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MLTAP has 5 Admission Scholorships of FSc MLT, BSc MLT & MSc MLT at Frontier Institute of Medical Sciences (FIMS), Abbotabad both on need & merit basis. Intreasted persons can contact us.
Meeting of MLTAP Delegate with Madam Bedar Bakhat, Principal College of Medical Lab Technology NIH, Islamabad. with senior faculty member to discuss the core issues of Medical Technologists & MLT Students.
Meeting of MLTAP Delegate with Prof. Dr. Zarfishan Tahir, Head of Bacteriology Lab. Institute of Public Health, Lahore, She Announced for Official Internship of 8 MLT Graduates in a year on rotation basis.
Medical Lab. Technologists Association of Pakistan (MLTAP) is going to organize its 5th National Seminar of MLT on " Molecular Advances in Diagnostics " at University of Health Sciences (UHS) Lahore on 06-11-2013 along with the Launch of MLTAP Scholarships for the deserving students of MLT.
info@mltap.com.pk
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MLTAP is going to collect The National Database of MLT's for on going efforts for the establishment of Allied Health Council / Pakistan Technologists Council. Please Provide Your Name, CNIC, Name of Institute, Professional Education, Place of Job, Date of Joining, Postal Address, Contact No., Email ID. at info@mltap.com.pk
MLTAP is going to arrange a Seminar on Quality Control & Techniques in Histopathology on 5th April, 2013 at Auditorium of COLLEGE OF MEDICAL LAB TECHNOLOGY NIH, ISLAMABAD.
A Tremendous Rally of MLTAP has been arranged on 1st May, World Labor Day 2012, to Highlight the core issues of Medical Technologists, specially for the seat creation of Medical Technologists at Tehsil, District and all teaching hospitals and for establishing Pakistan Technologist Council for the bright and secure future of our community.
Scholarship of MLTAP for poor and deserving students of MLT. Last date for submission of documents 31-12-2011
Seminar of Medical Lab. Technologists Association of Pakistan (MLTAP) on "Medical Technologists are the Backbone of Pathology" at the auditorium of Ziauddin Medical University/Hospital, Karachi on Tuesday, 20-09-2011.
A walk on World No Tobacco Day has been arranged on 31-05-2011 By Medical Lab. Technologists Association of Pakistan (MLTAP) for the nation of the awareness That "say no to tobacco"
National Pathology Week has jointly been arranged by CPSP and Medical Lab. Technologists Association of Pakistan (MLTAP), at Ziauddin Medical University/Hospital, Karachi.
A Tremendous Rally of MLTAP has been arranged on 1st May, World Labor Day 2011, to Highlight the core issues of Medical Technologists.
A Seminar on Molecular Biology & Lab Medicine is arranged by MLTAP on 10 Feb. 2011 at Auditorium of KEMU (King Edward Medical University, Lahore)
Job of Medical Technologist is available in Multan and Faisalabad region with attractive package through MLTAP, interesting MLT's send their c.v at info@mltap.com.pk
Two Flood relief camps have been arranged on the platform of MLTAP
Come to support your Nation
Admission for Condense Course of B.Sc MLT
Fatima Memorial College of Medicine & Dentistry and Institute of Allied Health Sciences in Affiliation with UHS Lahore
This is Two years Program. For more information contact with
Mr. Abu Bakar
Representative MLTAP
03334309005
A tremendous rally has been arranged in the favor and solidarity to Pakistani laborers on the occasion of world labor day in the platform of MLTAP
Publishing of news paper (Medical Journal)
Arranging of seminars
Registration of Members
Annual Conferences
Awareness Programs in all Medical Colleges and Institutes, Producing Lab. Technologists
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Medical Dictionary

  • A: Adenine, one member of the A-T (adenine-thymine) base pair in DNA. AA: Stands for amino acid, a building block of protein (and Alcoholics Anonymous). AAA: Many Americans know that the AAA ("triple A") is short for the American Automobile Association. Fewer may be aware that it is also the acronym for the American Association of Anatomists, one of a great multitude of professional societies in the health arena. Only a small selection of these is given as a sampler in this DICTIONARY. AAAS: American Association for the Advancement of Science. Spoken of as the "triple AS", an organization concerned not only with the biomedical sciences but with all sciences. The AAAS publishes the weekly journal "Science", one of the great scientific periodicals that carries a remarkable range of new information. including, for example, findings from the Apollo mission to Mars as well as reports from the project to map the human genome. AABB: American Association of Blood Banks. AACP: American Association of Child Psychiatry. AAD: American Association of Dermatology. AAFP: American Association of Family Practice. AAN: American Association of Neurology. AAO: Abbreviation for multiple organizations including American Association of Ophthalmology, American Association of Orthodontists, and American Academy of Otolaryngology. AAOS: American Academy of Orthopaedic Surgery. AAP: Abbreviation for multiple organizations including American Academy of Pediatrics, American Academy of Pedodontics, and American Academy of Periodontists. AAPMR: American Academy of Physical Medicine and Rehabilitation. Abdomen: The part of the body that contains the stomach, small intestine, colon, rectum, liver, spleen, pancreas, kidneys, appendix, gallbladder, and bladder. Abdominal cavity: The space between the abdominal wall and the spine. Abdominal hysterectomy: Surgical removal of the uterus through an incision made in the abdominal wall. As opposed to a vaginal hysterectomy. Abduction: Movement of a limb sideways away from the midline of the body. Abductor muscle: Any muscle used to pull a body part away from the midline of the body. For example, the abductor leg muscles serve to spread the legs. The opposite of "abductor" is "adductor." Aberration: A deviation, or irregularity. For example, a mental aberration is a significant deviation from normal mental activity. A chromosome aberration is a an abnormality in chromosome number or structure. Ablate: To remove, usually by cutting. At surgery a tumor may be ablated. Ablation: Removal or excision. Ablation is usually carried out surgically. For example, surgical removal of the thyroid gland (a total thyroidectomy) is ablation of the thyroid. The word ablation comes from the Latin ablatum meaning to carry away. ABO blood groups: The major blood group system. A person can be A, B, AB, or O. Abortion: In medicine, the premature exit of the products of conception from the uterus. A spontaneous abortion is a miscarriage. The miscarriage of 3 or more consecutive pregnancies is termed habitual abortion. Abortion, habitual: The miscarriage of 3 or more consecutive pregnancies. Recurrent abortion can be identically defined as 3 or more miscarriages (spontaneous abortions) with no intervening pregnancies. Habitual or recurrent abortion is a form of infertility. Abortion, multiple: Couples who have had 2 or more miscarriages (spontaneous abortions) have about a 5% chance that one member of the couple is carrying a chromsome translocation responsible for the miscarriages. Abortion, recurrent: See Abortion, habitual. Abrasion: 1. An Abrasion or "excoriation" is a wearing away of the upper layer of skin as a result of applied friction force. 2. In dentistry an "abrasion" is the wearing away of the tooth substance. Abruptio (abruptio placentae): Premature separation of the placenta from the wall of the uterus. Abruption is a potentially serious problem both for the mother and baby. Abscess: Abscess is a local accumulation of pus anywhere in the body. Abscess, peritonsillar: A persistent collection of pus behind the tonsil. Abscess, skin: Medical term for a common boil. Absolute CD4 count: The number of "helper" T-lymphocytes in a cubic millimeter of blood. With HIV, the absolute CD4 count declines as the infection progresses. The absolute CD4 count is frequently used to monitor the extent of immune suppression in persons with HIV. Also called a T4 count. Absorption: Uptake. Intestinal absorption is the uptake of food (or other substances) from the digestive tract. Acapnia: Less than the normal level of carbon dioxide in the blood. The opposite of hypercapnia. Accelerated phase of leukemia: Refers to chronic myelogenous leukemia that is progressing. The number of immature, abnormal white blood cells in the bone marrow and blood is higher than in the chronic phase, but not as high as in the blast phase. Accessory placenta: An extra placenta separate from the main placenta. Also called a succenturiate or supernumerary placenta. Accoucheur: French for a male obstetrician. Accoucheuse: French for a female obstetrician or midwife. ACE: Angiotensin converting enzyme. The angiotensins are peptides (smaller than proteins) that act as vasoconstrictors to narrow blood vessels. ACE inhibitors: Agents that inhibit ACE (angiotensin converting enzyme), thereby acting as vasodilators (really as anti-vasoconstrictors), lightening the stress load on the heart. Acentric: A chromosome fragment lacking a centromere (the "waist" of the chromosome essential for the division and the retention of the chromosome in the cell). Acetabulum: The cup-shaped socket of the hip joint. Acetylsalicylic acid: Aspirin. Achalasia: A failure of relaxation, especially of the muscle fibers at the junction of the esophagus and stomach. Achlorhydria: A lack of hydrochloric acid in the digestive juices in the stomach. Hydrochloric acid helps digest food. Achondroplasia: A genetic disorder of bone growth, the most common cause of short stature with disproportionately short arms and legs. ACL: See Anterior cruciate ligament. Acne: Localized skin inflammation as a result of overactivity of the oil glands at the base of hair follicles. When these oil glands become plugged up, the overactive oil glands become red and inflamed. Also called pimples. Acquired: In medicine, the word "acquired" means "new" or "added." New in the sense that it is not genetic (inherited) and added in the sense that is was not congenital (present at birth) but came along later. For example, AIDS is an acquired, not a genetic form of immune deficiency. Acquired immunodeficiency disease: Acquired immunodeficiency disease: Disease caused by infection with the human immunodeficiency virus (HIV). Acquired immunodeficiency syndrome: AIDS. Acquired mutation: A change in a gene or chromosome that occurs in a single cell after the conception of the individual. That change is then passed along to all cells descended from that cell. Acquired mutations are involved in the development of cancer. ACOG: American College of Obstetricians and Gynecologists. Acrocentric: A chromosome with a centromere near one end. Down syndrome (trisomy 21) is due to an extra acrocentic chromosome. Acrocyanosis: Blueness of the extremities (the hands and feet). Acrodermatitis enteropathica: An historic model for the therapy of genetic disease. In an era (the 1950s) when inherited disorders were usually seen as hopeless, this progressive hereditary (autosomal recessive) disease of children was found treatable. Acrodermatitis enteropathica is characterized by the simultaneous occurrence of skin inflammation (dermatitis) and diarrhea. The skin on the cheeks, elbows and knees and tissue about the mouth and anus are inflammed. There is also balding of the scalp, eyebrows and lashes, delayed wound healing and recurrent bacterial and fungal infections due to immune deficiency. The key laboratory finding is an abnormally low blood zinc level reflecting impaired zinc uptake. Treatment with zinc by mouth is curative. Acrodynia: Pain in the extremities. Acromegaly: Condition due to the production of too much growth hormone by the pituitary gland. Acromegaly is characterized by large structure of the tongue, forehead, hands, and feet. Actinic keratosis: A precancerous condition of thick and scaly patches of skin; also called solar or senile keratosis. Activity, drug: A measure of the physiological response a drug produces in the body. A less active drug produces less response (and visa versa). Active immunity: Immunity produced by the body in response to stimulation by a disease-causing organism or other agent. Activities of daily living (ADLs): The things we normally do in daily living including any daily activity we perform for self-care (such as feeding ourselves, bathing, dressing, grooming), work, homemaking, and leisure. The ability or inability to perform ADLs can be used as a very practical measure of ability/disability in many disorders. Acupuncture: The practice of inserting needles into the body with a therapeutic aim such as to reduce pain or induce anesthesia. Acute: Of short duration. Rapid and abbreviated in onset in reference to a disease process. (As opposed to chronic.) Acute leukemia: Cancer of the blood cells (leukemia) that characteristically comes on abruptly and (if not treated) progresses rapidly. ADA: American Dental Association (and the American Diabetes Association). Adam's apple: This familiar feature in front of the neck is due to forward protrusion of the largest cartilage of the larynx. It takes its name from the story that a piece of the forbidden fruit stuck in Adam's throat. ADD (Attention Deficit Disorder): An inability to control behavior due to difficulty in processing neural stimuli. Addison’s disease: Long-term underfunction of the outer portion of the adrenal gland. In medical terms, chronic insufficiency of the adrenal cortex. This may be due to a number of different insults to the adrenal including physical trauma, hemorrhage, and tuberculosis of the adrenal, and destruction of the cells in the pituitary gland that secrete ACTH (adrenocorticotropic hormone) which normally drives the adrenal. Addison’s disease is characterized by bronzing of the skin, anemia, weakness, and low blood pressure. The U.S. President J.F. Kennedy is said to have had Addison’s disease. Named after the British physician Thomas Addison (1793-1860). Adduction: Movement of a limb sideways toward the body. Adductor muscle: Any muscle that pulls inward toward the midline of the body. For example, the adductor muscles of the leg serve to pull the legs together. The opposite of "adductor" is "abductor." Adenine (A): One member of the base pair A-T (adenine-thymine) in DNA. Adenocarcinoma: A cancer that develops in the lining or inner surface of an organ. More than 95 percent of prostate cancers are adenocarcinoma. Adenoidectomy: The surgical removal of the adenoids. Adenoiditis: Infection of the adenoids. Adenoids: Masses of lymphoid tissue in the upper part of throat behind the nose. Adenoids and Tonsils: These celebrated structures in the back of the throat are composed of tissue similar to the lymph nodes or "glands." Adhesion: The union of two opposing tissue surfaces (often referring to the sides of a wound). Also refers to scar tissue strands that can form in an area of a previous operation, such as within the abdomen after a laparotomy. Adjuvant: Any substance that enhances the pharmacological effect of a drug or increases the ability of an antigen to stimulate the immune system. Adjuvant therapyTreatment given in addition to the primary treatment. ADLs: Activities of daily living. Adnexa: This Latin word (in the plural) is used in medicine in reference to appendages. For example, in gynecology the adnexa are the "appendages" of the uterus, namely the ovaries, Fallopian tubes and ligaments that hold the uterus in place. Adrenal glands: A pair of small glands, one located on top of each kidney. The adrenal glands produce hormones that help control heart rate, blood pressure, the way the body uses food, and other vital functions. Adrenaline: A substance produced by the medulla (inside) of the adrenal gland, adrenaline (the official name in the British Pharmacopoeia) is synonymous with epinephrine. Technically speaking, adrenaline is a sympathomimetic catcholamine. It causes quickening of the heart beat, strengthens the force of the heart’s contraction, opens up the bronchioles in the lungs and has numerous other effects. The secretion of adrenaline by the adrenal is part of the "fight-or-flight" reaction that we have in response to being frightened. Adult-onset Still’s disease: Although Still’s disease was first described in children, it is known to begin in adults. See: Still’s disease. Advance directives: See: Advance medical directives. Advance medical directives: Advance directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There ared two basic types of advance directives: (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for healthcare decision making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society). Adverse event: In pharmacology, an adverse event is any unexpected or dangerous reaction to a drug. Aerophagia: The word "phage" in Greek means "to eat." Aerophagia is literally to eat air. Aerophagia is a common cause of gas in the stomach. Everyone swallows small amounts of air when eating or drinking. However, rapid eating or drinking, chewing gum, smoking, or ill-fitting dentures may cause a significant increase in swallowed air. Aerosol: A fine spray or mist. An aerosol can be administered by a nebulizer and inhaled. Aetiology: The study of the causes, for example, of a disease. The word comes from the Greek "aitia", a cause + "logos", a discourse. Today in medicine the word "aetiology " is incorrectly used as a synonym for cause so often that it is fast becoming accepted usage, as in "the aetiology is unknown." Aetiology is the preferred spelling in some countries, including the U.K., whereas "etiology" without an "a" has taken over in the U.S. Afferent: Carrying away. Afferent comes from the Latin "ad", toward + "ferre", to bear = to carry toward. A vein is an afferent vessel since it carries blood toward from the heart. An afferent nerve carries impulses toward the central nervous system. The opposite of afferent is efferent. Afferent nerve: A nerve that carries impulses toward the central nervous system. Afferent vessel: A vessel carrying blood toward the heart. A vein or venule. African tapeworm: The beef tapeworm (Taenia saginata), the most common of the big tapeworms that parasitizes people, contracted from infected raw or rare beef. Can grow to be 12-25 feet (3.6-7.5 m) long in the human intestine. AFP: Abbreviation for alpha-fetoprotein AFO: Ankle-foot orthosis (a brace). African tick typhus: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (tache noire) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash. Also called fièvre boutonneuse. Afterbirth: The placenta + the fetal membranes that are normally expelled from the uterus after the birth of the baby. Hence, the "afterbirth." The placenta is of course the organ that joins the mother and fetus and permits the provision of oxygen and nutrients to the fetus and the release of carbon dioxide and waste products from the fetus to the mother. As humanity only disposable organ, the placenta is disk-shaped and at full term measures about 7 inches (18 cm) in diameter and a bit less than 2 inches (4 cm) thick. The fetal membranes—the chorion is the outer one and the amnion is the inner one—envelop the embryo and contain the amniotic fluid. The word "afterbirth" entered the English language in the 16th century. The term has also been applied to a child born after the father’s death or last testament. Agammaglobulinemia: Total (or nearly total) absence of the infection-fighting proteins (immunoglobulins) belonging to the class called gamma globulins. Can be due to certain genetic diseases or to acquired diseases such ad HIV. Agenesis: Lack of development of something. For example, agenesis of a toe means that toe failed to form. Agent, antihypertensive: As the name suggests, a drug aimed at reducing high blood pressure (hypertension). Agent, anti-infective: Something capable of acting against infection, by inhibiting the spread of an infectious agent or by killing the infectious agent outright. Agent, tocolytic: A medication that can inhibit labor, slow down or halt the contractions of the uterus. Tocolytic agents are widely used today to treat premature labor and permit pregnancy to procede and so let the fetus gain in size and maturity before being born. AIDS: Disease due to infection with the human immunodeficiency virus (HIV). AIDS is an acronym for Acquired ImmunoDeficiency Syndrome. Alpha-fetoprotein: A plasma protein, alpha-fetoprotein (AFP) is normally produced by the fetus. The level of AFP in the blood serum of pregnant women provides a screening test for open neural tube defects (anencephaly and spina bifida) and for Down syndrome (and other chromosome abnormalities) in the fetus. The maternal serum AFP (MSAFP) tends to be high with open neural tube defects and low with Down syndrome. AFP is also paradoxically produced by liver tumors (hepatomas) and germ cell tumors (teratocarcinoma and embryonal cell carcinomas) and so can be used to help detect and monitor the treatment of these tumors. Alpha interferon: The interferons are specialized proteins (lymphokines) produced by the body in response to an infection. these substances interfere with cell infection. There are 3 main classes of interferon, alpha, beta, and gamma. Alb-: Latin root form for the color white. Albinism: Partial or total lack of the pigment melanin in the skin, hair and iris. The word albino is Portuguese and comes from the Latin albus for white. Albino: A person with albinism. Albuginea: Tough white fibrous tissue. The tunica albuginea of the testis, for example, is the layer of dense whitish inelastic tissue that surrounds the testis. Albumen: "Albumen" with an "e" is the white of an egg, the part of the egg from which meringes are made. Albus in Latin is white. Albumin: "Albumin" with an "i" is the main protein in human blood. It is key to the regulation of the osmotic pressure of blood. Chemically, albumin is soluble in water, precipitated by acid, and coagulated by heat. Alcohol, pregnancy: The consumption of alcohol during pregnancy carries the danger of damaging the fetus. Aldosterone: Hormone produced by the outer portion (cortex) of the adrenal gland that regulates the balance of water and electrolytes (ions such as potassium and sodium) in the body. Aldosterone encourages the kidney to excrete potassium into the urine and retain sodium, thereby retaining water. Aldosterone is classified as a mineralocorticoid hormone. Aldosteronism: Overproduction of the hormone aldosterone from the cortex (the outer layer) of the adrenal gland or a tumor containing that type of tissue. Excess aldosterone (pronounced al’-do-ster-one) results in low potassium levels (hypokalemia), underacidity of the body (alkalosis), muscle weakness, excess thirst (polydipsia), excess urination (polyuria), and high blood pressure (hypertension). Also called hyperaldosteronism or Conn’s syndrome. Allele: An alternative form of a gene. Allergen: A substance that can allergic reaction. For examples, pollen, dander, mold. Allergic conjunctivitis: Inflammation of the whites of the eyes (the conjunctivae) with itching and redness of the eyes and tearing, due to allergy. Allergic reaction: A reaction that occurs when the immune system attacks a usually harmless substance (an allergen) that gains access to the body. The immune system calls upon a protective substance called immunoglobulin E (IgE) to fight these invading allergic substances ( allergens). Even though everyone has some IgE, an allergic person has an unusually large army of these IgE defenders -in fact, too many for their own good. This army of IgE antibodies attacks and engages the invading army of allergic substances of allergens. As is often the case in war, innocent bystanders are affected by this battle. These innocent bystanders are special cells called mast cells. These cells are frequently injured during the warring of the IgE antibodies and the allergic substances. When a mast cell is injured, it releases a variety of strong chemicals including histamine into the tissues and blood that frequently cause allergic reactions. These chemicals are very irritating and cause itching, swelling, and fluid leaking from cells. These allergic chemicals can cause muscle spasm and can lead to lung and throat tightening as is found in asthma and loss of voice. Allergic rhinitis: Medical term for hay fever, a condition due to allergy that mimicks a chronic cold. (Hay fever is a misnomer since hay is not a usual cause of this problem and there is no fever. Many substances cause the allergic symptoms in hay fever. Allergic rhinitis is the correct term for this allergic reaction. (Rhinitis means "irritation of the nose" and is a derivative of Rhino, meaning "nose.") Symptoms include nasal congestion, a clear runny nose, sneezing, nose and eye itching, and tearing eyes. Post-nasal dripping of clear mucus frequently causes a cough. Loss of smell is common and loss of taste occurs occasionally. Nose bleeding may occur if the condition is severe. Eye itching, redness, and tearing frequently accompany the nasal symptoms. Allergic rhinitis, perennial: Allergic rhinitis (hayfever) that occurs throughout the year. Allergic rhinitis, seasonal: Allergic rhinitis (hayfever) which occurs during a specific season. Allergic salute: The person with allergic rhinitis (hayfever) often rubs his/her nose using the index finger. This is the so-called "allergic salute." Allergy: A hypersensitivity of the body's immune system in response to exposure to specific substances (antigens), such as pollen, beestings, poison ivy, drugs, or foods. Anaphylactic shock is a severe form of allergy response which is a medical emergency. Symptoms of anaphylactic shock include dizziness, loss of consiousness, labored breathing, swelling of the tongue and breathing tubes, blueness of the skin, low blood pressure, and death. Allergy skin test: Test done on the skin to identify the allergy substance (allergen) triggering the allergic reaction. A small amount of the suspected allergy substance is placed on the skin. The skin is then gently scratched through the small drop with a special sterile needle. If the skin reddens and, more importantly, swells, then allergy to that substance is probable. Allergy desensitization: Stimulation of the immune system with gradually increasing doses of the substances to which a person is allergic, the aim being to modify or stop the allergy "war" (by reducing the strength of the IgE and its effect on the mast cells). This form of treatment is very effective for allergies to pollen, mites, cats, and especially stinging insects (eg, bees, hornets, yellowjackets, wasps, velvet ants, fire ants). Allergy immunotherapy usually takes 6 months to a year to become effective and injections ("shots") are usually required for 3-5 years. Allergy shots: See Allergy desensitization. Alloerotic: Having to do with sexual excitment toward the same sex. The opposite is heteroerotic. Alopecia: Baldness. There are many types of alopecia, each with a different cause. Alopecia can be localized to the front and top of the head, such as in male pattern baldness; patchy, such as in alopecia areata; or involve the entire head, such as in alopecia capitis totalis. Alopecia areata: Patchy baldness (alopecia means baldness and areata means occurring in patches). The problem typically begins with patchy hair loss on the scalp and sometimes progresses to complete baldness and even loss of body hair. Although alopecia areata affects 2.5 million people in the United States alone, little is known about its underlying causes. Stress, the immune system, and several different genes may play a part in causing alopecia areata. Alpha-1 antitrypsin deficiency: An inherited disease that results in low or no production of an important protein, alpha-1 antitrypsin. The lack of this protein leads to damage of various organs, but mainly to the lung and liver. Symptoms may become apparent at a very early age or in adulthood, manifesting either as shortness of breath or liver related symptoms (jaundice, fatigue, fluid in the abdomen, mental changes, or gastrointestinal bleeding). There are several options for treatment of the lung disease, including replacement of the missing protein. Treatment of the liver disease is a well-timed liver transplant Alpha error: The statistical error (said to be "of the first kind" or type I) made in testing an hypothesis when it is concluded that a result is positive when it really is not. Alpha error is often referred to as a false positive. ALS (Amyotropic Lateral Sclerosis): A chronic progressive disease of motor neurons (the nerves that come from the spinal cord to supply electrical energy to the muscles). Alternative medicine: Healing arts not generally taught in medical schools or typically practiced in hospitals. Alveoli: Tiny air sacs at the end of the bronchioles. Alzheimer's disease: A progressive degenerative disease of the brain that leads to dementia. On a cellular level, Alzheimer’s is characterized by unusual helical protein filaments in nerve cells (neurons) of the brain. These odd twisted filaments are called neurofibrillary tangles. On a functional level, there is degeneration of the cortical regions, especially the frontal and temporal lobes, of the brain. The U.S. President Ronald Reagan is said to have Alzheimer’s disease. Named after the German neurologist Alois Alzheimer (1864-1915). AMA: American Medical Association. Ambulance: Although you are undoubtedly familiar with the sound of the siren and the sight of the flashing lights of the ambulance, you may not necessarily know that the ambulance began as a walking hospital. The word "ambulance" indeed started off as a walking hospital, "un hôpital ambulant" in French, meaning literally "a walking hospital." The "hôpital ambulant" was devised during the campaigns of Napoleon to bring medical aid directly to his troops in the field. The original "hôpital ambulant" was a mobile unit designed to carry dressings and drugs to the wounded and evacuate the injured from the line of battle. The British, knowing a good idea when they saw it, came up with their own version of the "hôpital ambulant." But they economized by dropping the "hôpital" and corrupted "ambulant" to "ambulance." The French, of course, have for many years railed against the incursions of Anglo-Saxon words into the pure precincts of the French language. Nonetheless, they rejected their own "hôpital ambulant" and embraced the English "ambulance." So, in France today you can no longer see a hospital walking but "ambulances" are very much in evidence. Ambulant: Means the same as "ambulatory" (able to ambulate, walk about). Ambulatory: Able to ambulate, to walk about, not bed-ridden or hospitalized. Ambulatory care: Medical care (including diagnosis, observation, treatment and rehabilitation) provided on an outpatient basis. Ambulatory care is given to persons who are not confined to a hospital but rather are "ambulatory" and, literally, are able to ambulate or walk about. (A well-baby visit is considered ambulatory care even though the baby is not walking). American Type Culture Collection (ATTC): A key resource for cultured cells, located in Rockville, MD. AMI: Acute myocardial infarction (a heart attack). Amine: A chemical compound containing nitrogen. Amines are derived from ammonia. (The name "amine" was derived from the word "ammonia.") Amino acid: One of the building blocks of protein. The term "amino acids" dates to the middle of the 19th century. The idea that amino acids are "Bausteine" (building stones) came from the Nobel Prize winning German biochemist Albrecht Kossel (1853-1927). Amnesia: An impairment or lack of memory. Amnesia after a trauma event can be either antegrade (lack of memory related to events occurring after the event) or retrograde (lack of memory related to events occurring before the event). Amniocentesis: Procedure used in prenatal diagnosis to obtain amniotic fluid which can be used for genetic and other diagnostic tests. Informally called an "amnio." Amnion: A thin membrane surrounding the fetus during pregnancy. The amnion is the inner of the two fetal membranes (the chorion is the outer one). It contains the amniotic fluid. Amniotic fluid: The fluid bathing the fetus and serving as a shock absorber. Amplification: Event producing multiple copies of a gene or any sequence of DNA. Gene amplification plays a role in cancer. Amplification can occur in vivo (in the living individual) or in vitro (literally "in glass", or in a plastic vessel in the laboratory). Ampulla of Vater: A small projection into the duodenum through which bile and pancreatic secretions flow to mix with food for digestion. Amputation: Surgery to remove all or part of an arm, leg or digit (finger or toe). Amyloidosis: Disorder due to deposits of abnormal protein (amyloid) in body tissues. Amyotrophic lateral sclerosis (ALS): A chronic progressive disease of motor neurons (the nerves that come from the spinal cord to supply electrical energy to the muscles). ANA: See: Antinuclear antibodies. Anal fissure: Common tear in the anal canal. One of the common causes of red blood in the stool. Analgesia is the inability to feel pain. Anaphylactoid purpura: Also called Henoch-Schonlein purpura (HSP), this is a form of blood vessel inflammation, a vasculitis that affects small arterial vessels in the skin (capillaries) and the kidneys. HSP results in skin rash associated with joint inflammation (arthritis) and cramping pain in the abdomen. HSP frequently follows a bacterial or viral infection of the throat or breathing passages and is an unusual reaction of the body’s immune system to this infection. HSP occurs most commonly in children. HSP is generally a mild illness that resolves spontaneously, but sometimes it can cause serious problems in the kidneys and bowels. Treatment is directed toward the most significant area of involvement. Joint pain can be relieved by antiinflammatory medications, such as aspirin or ibuprofen. Some patients can require cortisone-related medications, such as prednisone, especially those with significant abdominal pain or kidney disease. Anastomosis: A procedure to connect healthy sections of the colon or rectum after the cancerous portion has been surgically removed. Anatomy: The study of form. Anatripsis: The use of friction as a treatment modality for a medical condition. Anatripsis may or may not also involve the application of a medicament. Androgen: A hormone that promotes the development and maintenance of male sex characteristics. Anemia is the condition of having less than the normal number of red blood cells or hemoglobin in the blood. The oxygen-transporting units are, therefore, insufficient. Patients can feel tired, fatigue easily, appear pale, develop palpitations, and become short of breath. There are many causes of anemia, including: bleeding, abnormal hemoglobin formation (such as in sickle cell anemia), iron, B12 (pernicious anemia), or folate deficiency, rupture of red blood cells (hemolytic anemia), and bone marrow diseases. Anemia, Cooley’s: Better known today as thalassemia (or as beta thalassemia or thalassemia major) .The clinical picture of this important type of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley. Another name for the disease is Mediterranean anemia. The name thalassemia was coined by the Nobel Prize winning pathologist George Whipple and the professor of pediatrics Wm Bradford at U. of Rochester because thalassa in Greek means the sea (like the Mediterrranean Sea) + -emia means in the blood so thalassemia means sea in the blood. Thalassemia is not just one disease. It is a complex contingent of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of normal adult hemoglobin is made up of 2 alpha and 2 beta polypeptide chains. In beta thalassemia, there is a mutation (change) in both beta globin chains leading to underproduction (or absence) of beta chains, underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin (for example, from Italy and Greece). Children with this disease inherit one gene for it from each parent. The parents are carriers (heterozygotes) with just one thalassemia gene, are said to have thalassemia minor, and are essentially normal. Their children affected with beta thalassemia seem entirely normal at birth because at birth we still have predominantly fetal hemoglobin which does not contain beta chains. The anemia surfaces in the first few months after birth and becomes progressively more severe leading to pallor and easy fatiguability, failure to thrive (grow), bouts of fever (due to infections) and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease. Anemia, iron deficiency: Deficiency of iron results in anemia because iron is necessary to make hemoglobin, the key molecule in red blood cells responsible for the transport of oxygen. In iron deficiency anemia, the red cells are unusually small (microcytic) and pale (hypochromic). Characteristic features of iron deficiency anemia in children include failure to thrive (grow) and increased infections. The treatment of iron deficiency anemia, whether it be in children or adults, is with iron and iron-containing foods. Food sources of iron include meat, poultry, eggs, vegetables and cereals (especially those fortified with iron). According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men. Anemia, Mediterranean: Better known today as thalassemia (or as beta thalassemia or thalassemia major) .The clinical picture of this important type of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley. The name thalassemia was coined by the Nobel Prize winning pathologist George Whipple and the professor of pediatrics Wm Bradford at U. of Rochester because thalassa in Greek means the sea (like the Mediterrranean Sea) + -emia means in the blood so thalassemia means sea in the blood. Thalassemia is not just one disease. It is a complex contingent of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of normal adult hemoglobin is made up of 2 alpha and 2 beta polypeptide chains. In beta thalassemia, there is a mutation (change) in both beta globin chains leading to underproduction (or absence) of beta chains, underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin (for example, from Italy and Greece). Children with this disease inherit one gene for it from each parent. The parents are carriers (heterozygotes) with just one thalassemia gene, are said to have thalassemia minor, and are essentially normal. Their children affected with beta thalassemia seem entirely normal at birth because at birth we still have predominantly fetal hemoglobin which does not contain beta chains. The anemia surfaces in the first few months after birth and becomes progressively more severe leading to pallor and easy fatiguability, failure to thrive (grow), bouts of fever (due to infections) and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease. Anemia, refractory: Anemia (a shortage of red blood cells) unresponsive to treatment. Anencephaly: Absence of the cranial vault and absence of most or all of the cerebral hemispheres of the brain. Anencephaly is a neural tube defect (NTD). It is due to abnormal development during embryonic life of the neural tube, the structure which gives rise to the central nervous system (the brain and spinal cord). Specifically, the upper end of the neural tube fails to close. Anencephaly is a uniformally lethal malformation. The risk of all NTDs including anencephaly can be decreased by the mother eating ample folic acid during pregnancy. Anesthesia: Loss of feeling or awareness. A local anesthetic causes loss of feeling in a part of the body. A general anesthetic puts the person to sleep. Anesthetic: A substance that causes lack of feeling or awareness. A local anesthetic causes loss of feeling in a part of the body. A general anesthetic puts the person to sleep. Aneuploidy: One or a few chromosomes above or below the normal chromosome number. For example, three number 21 chromosomes or trisomy 21 (characteristic of Down syndrome) is a form of aneuploidy. Aneurysm: A widening or dilatation of blood vessel. Angina: Angina is chest pain that is due to an inadequate supply of oxygen to the heart muscle. Angina trachealis: This has nothing whatsoever to do with the ordinary adult angina (angina pectoris) with chest pain of cardiac origin. Angina trachealis is more commonly known as croup, an infection of the larynx, trachea, and the bronchial tubes, largely in children. Caused usually by viruses, less often by bacteria. Symptoms include a cough that sounds like a barking seal and a harsh crowing sound during inhaling. Treatment can include moist air, salt water nose drops, decongestants and cough suppressants, pain medication, fluids, and occasionally antibiotics. The major concern in croup is breathing difficulty as the air passages narrow. Close monitoring of the breathing of a child with croup is important, especially at night. While most children recover from croup without hospitalization, some children can develop life-threatening breathing difficulties. Therefore, close contact with the doctor during this illness is important. Angioedema: Like hives but affects deeper skin layer. Angioedema, hereditary: A genetic form of angioedema. (Angioedema is also referred to as Quinke’s disease.) Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks. Also called hereditary angioneurotic edema. Angioid streaks: Tiny breaks in the elastin-filled tissue in the back of the eye (retinae). These abnormalities are visible to the doctor during an examination using a viewing instrument called an ophthalmoscope. Angioid streaks are seen in patients with pseudoxanthoma elasticum (abbreviated PXE), a rare disorder of degeneration of the elastic fibers with tiny areas of calcification in the skin, back of the eyes (retinae), and blood vessels. Angioid streaks can be associated with blindness. Angiogram: An x-ray of blood vessels, which can be seen because of an injection of a dye that shows up in the x-ray pictures. Angioneurotic edema, hereditary: A genetic form of angioedema. (Angioedema is also referred to as Quinke’s disease.) Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks. Also called hereditary angioedema. Angioplasty: Procedure with a balloon-tipped catheter to enlarge a narrowing in a coronary artery. Also called Percutaneous Transluminal Coronary Angioplasty (PTCA). Angiotensin: A family of peptides (smaller than proteins) that act as vasoconstrictors to narrow blood vessels. Angiotensin converting enzyme: Usually abbreviated ACE. Anhidrosis: Not sweating. From the Greek an- meaning not + hidros meaning sweat. Inability to sweat may seem a blessing but it is not, since to sweat is to be able to stay cool. Anhidrosis creates a dangerous inability to tolerate heat. Ankle-foot orthosis (AFO): A brace (usually plastic) worn on the lower leg and foot to support the ankle, hold the foot and ankle in the correct position, and correct foot drop. Ankle pain: The ankle is a "hinged" joint. The severity of ankle sprains ranges from mild (which can resolve within 24 hours) to severe (which can require surgical repair). Tendinitis of the ankle can be caused by trauma or inflammatory forms of arthritis. Ankylosing spondylitis: A type of arthritis that causes chronic inflammation of the spine. Anomaly: Something abnormal. A congenital anomaly is a birth defect. Anonymous reporting: In public health, anonymous reporting permits the acquisition of certain data such as the proportion of persons with a positive test or with a disease. Anonymous testing: Testing in which no name is used—there is total anonymity—to identify the person tested. For example, the State of Florida requires that each county have a site for anonymous HIV testing. Anorexia: A decreased appetite or aversion to food. Anorexia nervosa is a serious psychological disorder characterized by an extreme aversion to food, most often affecting young women. Anorexia nervosa: A decreased appetite or aversion to food. Anorexia nervosa is a serious psychological disorder characterized by an extreme aversion to food, most often affecting young women. Anosmia: No sense of smell. Anoxia: Lack of oxygen. Anterior cruciate ligament (ACL): One of the ligaments in the knee, the ACL crosses from bottom of the femur (the thigh bone) to the top of the tibia (the main bone in the lower leg). ACL injuries can occur in a number of situations including sports, such as football. Anthrax: A serious infection, anthrax is not primarily a human disease but rather an infection of animals. Cattle, sheep, horses, mules, and some wild animals are highly susceptible. Humans (and swine) are generally resistant to anthrax. Anthrax can take different forms. With the lung form of the disease. People inhale the anthrax spores and, if untreated, are likely to die. An intestinal form is caused by eating meat contaminated with anthrax. But most human anthrax comes from skin contact with animal products. Cutaneous (skin) anthrax was once well known among people who handled infected animals, like farmers, woolsorters, tanners, brushmakers and carpetmakers in the days when the brushes and carpets were animal products. The hallmark of skin anthrax is a carbuncle, a cluster of boils, that ulcerates in an ugly way. Typically this lesion has a hard black center surrounded by bright red inflammation. This accounts for its name, "anthrax", the Greek word for "coal", a burning coal. Anthrax has become the stuff, unfortunately, of frontpage news as a possible agent of biological warfare. Anthrax immunization: A series of six shots over six months and booster shots annually, the anthrax vaccine now in use in the USA was first developed in the 1950s and approved by the Food and Drug Administration for general use in 1970. It is produced by the Michigan Biologic Products Institute of Michigan’s Department of Health and is given routinely to veterinarians and others working with livestock. In December, 1997 it was announced that all US military would receive the vaccine, as do the military in the UK and Russia, the reason being concern that anthrax might be used in biologic warfare. Antibiotics: Drugs that fight infections. Antibiotic resistance: The ability of bacteria and other microorganisms to withstand an antibiotic to which they were once sensitive (and were once stalled or killed outright). Also called drug resistance. Antibodies are specialized proteins produced by white blood cells that circulate in the blood seeking and attaching to foreign proteins, microorganisms or toxins in order to neutralize them. They are part of the immune system. (see immune system). Antibodies, antinuclear (ANA): See: Antinuclear antibodies. Anticipation: The progressively earlier appearance and increased severity of a disease from generation to generation. The phenomenon of "anticipation" was once thought to be an artifact but a biological basis for it has been discovered in a number of genetic disorders such as myotonic dystrophy and Huntington's disease. Anti-coagulant agents: Medications, like heparin, used as "blood-thinners" to prevent blood clots and to maintain open blood vesssels. Anticholinergic: The action of certain medications that inhibit the transmission of parasympathetic nerve impulses and thereby reduce spasms of smooth muscle (such as t6hat, for example, in the bladder). Antinuclear antibodies (ANA): Antibodies directed against the nucleus of a cell. The ANA test is almost always positive (indicative of the presence of antinuclear antibodies) in systemic lupus erythematosus (SLE). It may also be positive in other connective tissue diseases such as rheumatoid arthritis and scleroderma. Antigen: Something potentially capable of inducing an immune response. Antibodies are elicited by antigens. Antihistamines: Drugs that combat the histamine released during an allergic reaction by blocking the action of the histamine on the tissue. Antihistamines do not stop the formation of histamine nor do they stop the conflict between the IgE and antigen. Therefore, antihistamines do not stop the allergic reaction but protect tissues from some of its effects. Antihistamines frequently cause mouth dryness and sleepiness. Newer "non sedating" antihistamines are generally thought to be somewhat less effective. Antihistamine side effects that very occasionally occur include urine retention in males and fast heart rate. Antihypertensive: Something that reduces high blood pressure (hypertension). Anti-infective: Something capable of acting against infection, by inhibiting the spread of an infectious agent or by killing the infectious agent outright. Antiphospholipid antibody syndrome: An immune disorder characterized by the presence of abnormal antibodies in the blood associated with certain medical conditions including abnormal blood clotting, migraine headaches, premature miscarriage, and low blood platelet counts (thrombocytopenia). Anti-platelet agents: Medications that, like aspirin, reduce the tendency of platelets in the blood to clump and clot. Antiseptic: Something that discourages the growth microorganisms. By contrast, aseptic refers to the absence of microorganisms. Antitoxin: An antibody from the serum of an animal stimulated with specific antibodies, used to provide passive immunity. For example, if a child gets whooping cough (diphtheria), an antitoxin prepared in horses against diphtheria may be useful in treatment. The antitoxin can only be of short-term value because the antibodies against diphtheria were made by the horse and the child is just the passive recipient of the antibodies. Antrum: A general term for cavity or chamber which may have specific meaning in reference certain organs or sites in the body. The antrum of the stomach (gastric antrum) is a portion before the outlet which is lined by mucosa which does not produce acid. The paranasal sinuses can be referred to as the frontal antrum, ethmoid antrum, and maxillary antrum. Ants, fire: Originally from S. America. Among the worst insect pests ever to invade the U.S. Red or yellowish ants of small-to-medium size with a severe sting that burns like fire. They normally feed on small insects but, with denser populations, they eat seeds and seedling plants, damage grain and vegetable crops, invade kitchens, attack newly hatched poultry and the young of ground-nesting wild birds. Fire ants can kill newborn domestic and wild animals. Each colony is composed of a queen, winged males and females and 3 kinds of workers. A nest averages about 25,000 workers, but far larger populations are common. Semipermanent nests are large mounds of excavated soil with openings for ventilation. Since nests may number 50-100 (or more) in a heavily infested field, cultivating becomes difficult (or impossible). Fire ants belong to the genus Solenopsis. Ants, fire (stings from): Also called thief ants, a scourge, these red or yellow ants of small-to-medium size, originally from South America, have a severe sting that burns like fire and can trigger an allergic reaction. Avoidance and prompt treatment are essential. Ants, velvet (stings from): Common in most parts of the world including the Southern and Southwestern U.S., velvet ants are not true ants but rather parasitic wasps. Their sting can trigger allergic reactions. Avoidance, prompt treatment and, in selected cases, allergy injection therapy are useful. Anus: The opening of the rectum to the outside of the body. Aorta: The great (main) artery from the left ventricle of the heart. Aortic insufficiency (regurgitation): Sloshing of blood back down from the aorta into the left ventricle due to incompetancy of the aortic valve. Aortic stenosis: Narrowing (stenosis) of the valve between the left ventricle of the heart and the aorta, impeding the delivery of blood via the aorta to the body. Aortic valve: Valve at the base of the aorta that prevents backflow of blood from the aorta into the left ventricle of the heart. AP: AP is a versatile abbreviation. It serves in cardiology to abbreviate angina pectoris (AP) and arterial pressure (AP). In endocrinology, it stands for the anterior pituitary (AP). And in anatomy, AP means anteroposterior, i.e., from front-to-back. AP, X-ray: An X-ray picture in which the beams pass from front-to-back (anteroposterior). As opposed to a PA (posteroanterior) film in which the rays pass through the body from back-to-front. Apex: From the Latin meaning summit, the apex is the tip of a pyramidal or rounded structure, like the lung or the heart. The apex of the lung is indeed its tip, its rounded most superior portion. The apex of the heart is likewise its tip, but that is formed by the left ventricle so it is essentially the most inferior portion of the heart. Apgar: Short for Apgar score. Apgar score: A practical method to assess a newborn infant, the Apgar score is a number arrived at by scoring the heart rate, respiratory effort, muscle tone, skin color, and response to a catheter in the nostril. Each of these objective signs can receive 0, 1, or 2 points. An Apgar score of 10 means an infant is in the best possible condition. The Apgar score is done routinely 60 seconds after the complete birth of the infant. An infant with a score of 0-3 needs immediate resusitation. The Apgar score is commonly repeated 5 minutes after birth and in the event of a difficult resusitation, the Apgar may be done again at 10, 15, and 20 minutes. An Apgar score of 0-3 at 20 minutes of age is predictive of high morbidity (disease) and mortality. The score is named for the American anesthesiologist Virginia Apgar (1909-1974) at Columbia University in New York who invented the scoring method. Aphasia: Literally aphasia means no speech. Aphasia can apply to a defect in expression or comprehension. Aphonia: Inability to speak. Apical: The adjective for apex, the tip of a pyramidal or rounded structure, like the lung or the heart. For example, an apical lung tumor is a tumor located at the top of the lung. Aplasia: Failure to develop. If something develops and then wastes away, that is atrophy. Aplastic anemia: Anemia due to failure of the bone marrow to produce red blood cells. Apnea: The absence of breathing (respirations). Appendectomy: Removal of the appendex by surgery. Appendicitis: Inflammation of the appendix. Appendix (vermiform appendix): A small outpouching from the beginning of the large intestine. Formally called the vermiform appendix because it is wormlike. Appendix epididymis: A small cystic projection from the surface of the epididymus which represents a remnant the embryologic mesonephros. Appendix epiploica: A finger-like projection of fat attached to the colon. Appendix testis: A small solid projection of tissue on the outer surface of the testis which is a remnant of the embryologic mullerian duct. Apthous ulcers: These small sensitive painful craters in the mouth are common canker sores. There are many possible causes of apthous ulcers and frequently the cause is unknown. Aqueduct: A channel for the passage of fluid. Aqueduct of Sylvius: A canal between two of the cavities (called the third and fourth ventricles) in the brain through which cerebrospinal fluid passes. Arachnodactyly: Long spider-like fingers and toes. Arborvirus: Although arbor sounds as if it should have something to do with trees, it doesn’t. It comes from the first 2 letters of "arthropod" + the first 3 letters of "borne." Arborviruses are transmitted (borne) to humans by mosquitoes and ticks (arthropods). Archaea: A unique group of microorganisms. They are called bacteria (Archaeobacteria) but they are genetically and metabolically different from all other known bacteria. They appear to be living fossils, the survivors of an ancient group of organisms that bridged the gap in evolution between bacteria and the eukaryotes (multicellular organisms). The name Archaea comes from the Greek archaios meaning ancient. Arcus senilis: A cloudy opaque arc or circle around the edge of the eye, often seen in the eye of the elderly. Areolus: The diminuitive of the Latin "area" meaning a little space or park. The areolus of the breast is the small darkened area around the nipple. Armed tapeworm: The pork tapeworm (Taenia solium). Contracted from undercooked or measly pork (pork infected with the larval forms of the tapeworm). Can grow to be 3-6 feet (0.9-1.8 m) long in the human intestine. Also known as the measly tapeworm. Arrayed library: In genetics, an arrayed library consists of (in technical terms) individual primary recombinant clones which are hosted in phage, cosmid, YAC, or another vector that have been placed in two- dimensional arrays in microtiter dishes (plastic dishes with an orderly array of tiny wells). Each primary clone can be identified by the identity of the plate and the clone location (row and column) on that plate. Arrayed libraries of clones are used for many purposes, including screening for a specific gene or genomic region. The information gathered on individual clones from genetic linkage and physical map studies is then entered into a database and used to construct physical and genetic linkage maps Arrector pili: A microscopic band of muscle tissue which connects a hair follicle to the dermis. When stimulated, the arrector pili will contract and cause the hair to become more perpendicular to the skin surface (stand on end). Arrhythmias: Abnormal heart rhythms. The heartbeats may be too slow, too rapid, irregular, or too early. Rapid arrhythmias (greater than 100 beats per minute) are called tachycardias. Slow arrhythmias (slower than 60 beats per minute) are called bradycardias. Irregular heart rhythms are called fibrillations (as in atrial fibrillation). When a single heartbeat occurs earlier than normal, it is called a premature contraction. Arrhythmias, atrial: Abnormal heart rhythm due to electrical disturbances in the atria (the upper chambers of the heart) or the AV node "relay station", leading to fast heart beats. Examples of atrial arrhythmias includes atrial fibrillation, atrial flutter, and paroxysmal atrial tachycardia (PAT). Arrhythmias, rapid: Abnormally rapid heart rhythms, medically termed tachycardia. Arrhythmias, slow: Abnormally slow heart rhythms, medically termed bradycardia. Arrhythmias, ventricular: Abnormal rapid heart rhythms (arrhythmias) that originate in the lower chambers of the heart (the ventricles). Ventricular arrhythmias include ventricular tachycardia and ventricular fibrillation. Both are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack. Arterial tension: The pressure of the blood within an artery, the arterial pressure. Also called the intra-arterial pressure. Arteriogram: An x-ray of blood vessels, which can be seen after an injection of a dye that shows up in the x-ray pictures. Arteriole: A small branch of an artery that leads to a capillary. Arteriosclerosis: Hardening and thickening of the walls of the arteries. Arthritis: Inflammation of a joint. When joints are inflamed they can develop stiffness, warmth, swelling, redness and pain. There are over 100 types of arthritis. (see osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, lupus, gout, pseudogout). Arteritis, cranial: A serious disease characterized by inflammation of the walls of the blood vessels (vasculitis). The vessels affected are the arteries (hence the name "arteritis"). The age of affected patients is usually over 50 years of age. Cranial arteritis is also known as temporal arteritis and as giant cell arteritis. It can lead to blindness and/or stroke. The disease is detected by a biopsy of an artery. It is treated with high dose cortisone-related medications. Artery: A blood vessel that carries blood away from the heart. Put otherwise, an artery is an efferent vessel (efferent coming from the Latin "ex’, out + "ferre", to bear = to bear out or carry away). Arterial blood is normally full of oxygen. The oxygenated hemoglobin (oxyhemoglobin) makes it look bright red. Arthralgia: Pain in the joints. The Greek "algos" means "pain." Arthritis, degenerative: A type of arthritis caused by inflammation, breakdown, and eventual loss of the cartilage of the joints. Also called osteoarthritis. Arteritis, giant cell: A chronic vascular disease, most often involving the carotid artery system, that can lead to blindness and/or stroke, Giant cell arteritis (also called temporal arteritis) is detected by a biopsy of an artery, and is treated with high dose cortisone. Arthritis, gout: Joint inflammation caused by uric acid crystal deposits in the joint space An attack is usually extremely painful.The uric acid crystals are deposited in the joint fluid (synovial fluid) and joint lining (synovial lining). Intense joint inflammation occurs as white blood cells engulf the uric acid crystals, causing pain, heat, and redness of the joint tissues. The term "gout" commonly is used to refer to these painful arthritis attacks but gouty arthritis is only one manifeatation of gout. Arthritis in children: Arthritis is not just a problem for the retired. It can and does affect children in the form of juvenile/pediatric arthritis. > Arthritis, Lyme: Inflammation of the joints associated with Lyme disease, a bacterial disease spread by ticks. Arthritis, psoriatic: Joint inflammation associated with psoriasis. Arthritis, quackery: Like many people with chronic ailments, sufferers from arthritis are potentially vulnerable to proponents of "cure-all" treatments which are promoted as having great benefits, but in reality have no right to such claims. Arthritis, Reiter's: The combination of inflammation of the joints (arthritis), eyes (conjunctivitis), and GU (genitourinary) &/or GI (gastrointestinal) systems. Arthritis, rheumatoid: Autoimmune disease that is characterized by chronic inflammation of the joints and can cause inflammation of tissues in other areas of the body (such as the lungs, heart, and eyes). Arthritis, spondylitis: A form of arthritis causing chronic inflammation of the spine. Arthritis, systemic-onset chronic rheumatoid : See: Arthritis, systemic-onset juvenile rheumatoid (Still’s disease). Arthritis, systemic-onset juvenile rheumatoid (Still’s disease): A form of joint disease, arthritis, that presents with systemic (bodywide) signs and symptoms including high intermittent fever, a salmon-colored skin rash, swollen lymph glands, enlargement of the liver and spleen, and inflammation of the lungs (pleuritis) and around the heart (pericarditis) The arthritis itself may not be immediately apparent but in time it surfaces and may persist after the systemic symptoms are long gone. Also known as systemic-onset juvenile chronic arthritis. Arteritis, temporal: Also called giant cell arteritis or cranial arteritis, this is a serious disease characterized by inflammation of the walls of the blood vessels (vasculitis). The vessels affected by inflammation are the arteries (hence the name "arteritis"). The age of affected patients is usually over 50 years of age. Giant cell arteritis can lead to blindness and/or stroke. It is detected by a biopsy of an artery. It is treated with high dose cortisone. Arthroscopy is a surgical technique whereby a doctor inserts a tube-like instrument into a joint to inspect, diagnose and repair tissues. It is most commonly performed in patients with diseases of the knees or shoulders. Articulation: The joining of two structures. From the Latin "articulus," meaning a joint. There are diverse application of the word "articulation" including: (1) in medicine, the place where bones come together, that is the joint; (2) in dentistry, the place where teeth come together, the occlusal surfaces of the teeth; and (3) in speech, the production of intelligible words and sentences, again by joining, but in this case by joining together properly the structures such as the lips, tongue and palate needed to articulate speech. Artery: An Artery is a blood vessel that carries blood high in oxygen content from the heart throughout the body. It is the part of the circulatory system Asbestos: A natural material that is made up of tiny fibers. If the fibers are inhaled, they can lodge in the lungs and lead to cancer, such as mesothelioma, or a scarring of the lungs, called asbestosis. Ascaris: Intestinal roundworms. Ascites: Abnormal buildup of fluid in the abdomen. Ascites can occur as a result of severe liver disease. ASD: Acronym for atrial septal defect. Aseptic: The absence of microorganisms. By contrast, something that just discourages the growth of microorganisms is antiseptic. Aseptic bursitis: Inflammation of a bursa that is not caused by infection. A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known as "bursitis." Most commonly this is not an infectious condition (aseptic bursitis). Aseptic necrosis: Condition in which poor blood supply to an area of bone leads to bone death. Also called avascular necrosis and osteonecrosis. Asphyxia: Impaired or impeded breathing. Aspirate: To suck in. A patient may aspirate for example by accidentally drawing material from the stomach into the lungs. A doctor can aspirate a joint. Aspiration: Removal of a sample of fluid and cells through a needle. Aspiration also refers to the accidental sucking in of food particles or fluids) into the lungs. Aspiration pneumonia: Inflammation of the lungs due to aspiration (the sucking in of food particles or fluids into the lungs). Aspirin: A good example of a tradename that entered into the language, Aspirin was once the Bayer trademark for acetylsalicylic acid. Assistive device: Any device that is designed, made, or adapted to assist a person perform a particular task. For examples, canes, crutches, walkers, wheel chairs, and shower chairs are all assistive devices. Asthma: Breathing problem due to reversible narrowing of airways (bronchospasm). Astigmatism: A common kind of impaired vision in which part of an image is not sharp. Due to unequal curvature of the refractive surfaces of the eye. Ataxia: Wobbliness. Ataxia is incoordination and unsteadiness due to the brain’s failure to regulate the body’s posture and regulate the strength and direction of limb movements. Ataxia is usually a consequence of disease in the brain, specifically in the cerebellum which lies beneath the back part of the cerebrum. Ataxia, cerebellar: See: Ataxia. Ataxia-telangiectasia (AT): A genetic disease with a wobbly gait and "red eye" due to widening of small blood vessels in the conjunctiva of the eye. AT carries with it an increased risk of leukemia and lymphoma. ATCC: American Type Culture Collection ( a key resource for cultured cells, located in Rockville, MD). Athetosis: Involuntary writhing movements particularly of the arms and hands. Athlete's foot: A skin infection caused by a fungus called Trichophyton which can thrive and infect the upper layer of the skin when the feet (or other areas of the body) remain moist, warm, and irritated. The fungus can be found on floors and in socks and clothing and can be spread from person to person by contact with these objects. However, without proper growing conditions (a warm, moist environment), the fungus will not infect the skin. Atresia: Failure of a structure to be tubular. Esophageal atresia is a birth defect in which part of esophagus is not hollow. With anal atresia, there is no hole at the bottom end of the intestine. Atria: The plural of atrium. Atrial arrhythmias: See Arrhythmias, atrial. Atrial fibrillation: Abnormal irregular heart rhythm with chaotic generation of electrical signals in the atria of the heart. Familiarly called atrial fib. Atrial septal defect (ASD): A hole in the septum, the wall, between the atria, the upper chambers of the heart. Commonly called an ASD. ASDs constitute a major class of heart formation abnormalities present at birth (congenital cardiac malformations). Normally, when clots in veins break off (embolize) , they travel first to the right side of the heart and, then to the lungs where they lodge. The lungs act as a filter to prevent the clots from entering the arterial circulation. However, when there is an ASD, a clot can cross from the right to the left side of the heart, then pass into the arteries as a paradoxical embolism. Once in the arterial circulation, a clot can travel to the brain, block a vessel there, and cause a stroke (cerebrovascular accident). Because of the risk of stroke from paradoxical embolism, it is usually recommended that even small ASDs be closed (repaired). Atrial septum: The wall between the two upper chambers (the right and left atrium) of the heart. Atrio-ventricular node: See AV node. Atrium: An entry chamber. On both sides of the heart, the atrium is the chamber leading to the ventricle. Atrophy: Wasting away or diminuition. Muscle atrophy is wasting of muscle, decrease in muscle mass. Attention deficit disorder (ADD): An inability to control behavior due to difficulty in processing neural stimuli. Attenuated virus: A weakened virus that is no longer virulent. Can be used to make a live virus vaccine. Audiogram: A test of hearing at a range of sound frequencies. Audiology: The study of hearing. Audiometry: The measurement of hearing. Aura: A premonition. There is often an aura before a migraine or a grand mal seizure. The aura, a symptom of brain malfunction, may consist of flashing lights, a gleam of light, blurred vision, an odor, the feeling of a breeze, numbness, weakness, or difficulty speaking. Auricle: The ear (actually, the pinna which is the principal projecting part of the ear) or something that is ear shaped like the upper chamber (atrium) of the heart. Auricular: Of or pertaining to the outer ear. Adjective form of auricle. (Not to be confused with avuncular which refers to an uncle). Auscultate: To listen to the sounds made by the internal organs of the body for diagnostic purposes. For example, nurses and doctors auscultate the lungs and heart of a patient by using a stethoscope placed on the patient's chest. Autism: Impaired development in social interaction, communication and behavior. Autoclave: A chamber for sterilizing with steam under pressure. The original autoclave was essentially a pressure cooker. The steam tightened the lid. The device was called an autoclave (from the Greek auto, self + clavis, key) meaning self-locking. Autogenous: Self-produced. Autoimmune diseases are illnesses which occur when the body tissues are attacked by its own immune system. The immune system is a complex organization within the body that is designed normally to "seek and destroy" invaders of the body, particularly infections. Patients with these diseases have unusual antibodies in their blood that target their own body tissues. Autonomic nervous system: Part of the nervous system once thought functionally independent of the brain. The autonomic nervous system regulates key functions including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The autonomic nervous system has two divisions: (1) the sympathetic nervous system that accelerates the heart rate, constricts blood vessels, and raises blood pressure; and (2) the parasympathetic nervous system slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles. Autopsy: Postmortem examination. Also called a necropsy. Autoradiography: A technique using X- ray film to visualize molecules or fragments of molecules that have been radioactively labeled. Autoradiography has many applications in the laboratory. Autoradiography can, for example, be used to analyze the length and number of DNA fragments after they are separated from one another by a method called gel electrophoresis. Autosome: Any chromosome other than the X and Y sex chromosome People normally have 22 pairs of autosomes (44 autosomes) in each cell. AV node: Specialized heart tissue which acts as an electrical relay station between the atria and the ventricles. Electrical signals from the SA node and the atria must pass through the AV node to reach the ventricles. (The SA node is the pacemaker of the heart and is situated in the right atrium.) Avascular necrosis: Condition in which poor blood supply to an area of bone leads to bone death. Also called avascular necrosis and osteonecrosis. Avulsion: Tearing away. A nerve can be avulsed by an injury, as can part of a bone. Axilla: Armpit. Axillary dissection: An axillary dissection means removal of a portion of the lymph nodes under the arm. Azotemia: A higher than normal blood level of urea or other nitrogen containing compounds in the blood. The hallmark test is the serum BUN (blood urea nitrogen) level. Usually caused by the inability of the kidney to excrete these compounds.
  • B cells: A type of white blood cell. Many B cells mature into plasma cells, which can produce antibody proteins necessary to fight off infections, such as viruses. 
    Baby, fetal alcohol syndrome: Alcohol is capable of causing birth defects. FAS (fetal alcohol syndrome) always involves brain damage. and impaired growth. FAS also always involves head and face abnormalities. No amount of alcohol has been proven safe during pregnancy. Women who are or may become pregnant are advised to avoid alcohol. 

    Back pain, low: Symptoms in the low back can relate to the bony lumbar spine, discs between the vertebrae, ligaments around the spine and discs, spinal cord and nerves, muscles of the low back, internal organs of the pelvis and abdomen, and the skin covering the lumbar area. The low back, or lumbar area, functions in structural support, movement, and protection of certain body tissue. 

    Bacteria: are single-celled microorganisms which can live as either independent organisms or as parasites. It is a bacteria that is responsible for the common throat infection "Strep throat." 

    Bacteriophage: A virus that naturally lives within a bacterial cell. Much used in molecular genetics and cell biology. Known commonly as phage. 

    "Bad" cholesterol: Low-density lipoprotein (LDL) cholesterol. 

    Baker’s cyst: A swelling in the space behind the knee (the popliteal space) composed of a membrane-lined sac filled with synovial fluid that has escaped from the joint. Named after the British surgeon William Morrant Baker (1839-1896). Also called a synovial cyst of the popliteal space. 

    Baldness: Alopecia. There are many types of baldness, each with a different cause. Baldness can be localized to the front and top of the head, such as in male pattern baldness; patchy, such as in alopecia areata; or involve the entire head, such as in alopecia capitis totalis. 

    Baldness, patchy: Medically referred to as alopecia areata (alopecia means baldness and areata means occurring in patches). The problem typically begins with patchy hair loss on the scalp and sometimes progresses to complete baldness and even loss of body hair. Although alopecia areata affects 2.5 million people in the United States alone, little is known about its underlying causes. Stress, a disordered immune system, and several different unknown genes may possibly play a part. 

    Balloon angioplasty: Coronary angioplasty is accomplished using a balloon-tipped catheter inserted through an artery in the groin or arm to enlarge a narrowing in a coronary artery. Coronary artery disease occurs when cholesterol plaque builds up (atherosclerosis) in the walls of the arteries to the heart. Angioplasty is successful in opening coronary arteries in 90% of patients. 40% of patients with successful coronary angioplasty will develop recurrent narrowing at the site of balloon inflation. 

    Banding of chromosomes: Treatment of chromosomes to reveal characteristic patterns of horizontal bands. Thanks to these banding patterns that resemble bar codes, each human chromosome is distinctive and can be identified without ambiguity. 

    Barium enema: A series of x-rays of the lower intestine. The x-rays are taken after the patient is given an enema with a white, chalky solution that contains barium. The barium outlines the intestines on the x-rays. 

    Barium solution: A liquid containing barium sulfate, which shows up on x-rays. It outlines organs of the body so they can be seen on x-ray film. 

    Barium swallow: An upper gastrointestinal series (barium swallow) is an X-ray test used to define the anatomy of the upper digestive tract. Women who are or may be pregnant should notify the doctor requesting the procedure and the radiology staff. The test involves filling the esophagus, stomach, and small intestines with a white liquid material (barium). 

    Barlow’s syndrome: Barlow’s syndrome is mitral valve prolapse (also known as "click murmur syndrome"), the most common heart valve abnormality, affecting 5-10% of the world population. Most patients have no symptoms and require no treatment. However, the condition can be associated with fatigue and/or palpitations. The mitral valve prolapse can often be detected by a doctor during examination of the heart and can be confirmed with an echocardiogram. Patients are usually given antibiotics prior to any procedure which might introduce bacteria into the bloodstream, including dental work and minor surgery. 

    Barr body: A microscopic feature of female cells due to the presence of two X chromosomes in the female. One of these X chromosomes is inactive and is crumpled up to form the Barr body. 

    Barrett's esophagus: A change in the cells of the tissue that lines the bottom of the esophagus. The esophagus may become irritated when the contents of the stomach back up (reflux). Reflux that happens often over a period of time can lead to Barrett's esophagus. Barrett’s esophagus is a risk factor in esophageal cancer. 

    Basal cells: Small, round cells found in the lower part, or base, of the epidermis, the outer layer of the skin. 

    Basal cell carcinoma: A type of skin cancer in which the cancer cells resemble the basal cells of the epidermis. 

    Basal metabolic rate: A measure of the rate of metabolism. For example, someone with an overly active thyroid will have an elevated basal metabolic rate. 

    Base in DNA: A unit of the DNA. There are 4 bases: adenine (A), guanine (G), thymine (T), and cytosine (C). The sequence of bases (for example, CAG) is the genetic code. 

    Base pair: Two DNA bases complementary to one another (A and T or G and C) that join the complementary strands of DNA to form the double helix characteristic of DNA. 

    Base sequence: The order of nucleotide bases (A,T, G, C) in a DNA molecule. 

    Base sequence analysis: A method for determining the order of nucleotide bases in DNA. 

    Battle fatigue: The World War II name for what is known today as post-traumatic stress, this is a psychological disorder that develops in some individuals who have had major traumatic experiences (and, for example, have been in a serious accident or through a war). The person is typically numb at first but later has symptoms including depression, excessive irritability, guilt (for having survived while others died), recurrent nightmares, flashbacks to the traumatic scene, and overreactions to sudden noises. Post-traumatic stress became known as such in the 70s due to the adjustment problems of some Vietnam veterans. 

    Bee stings: Stings from bees and other large stinging insects such as yellow jackets, hornets and wasps can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A’s" of insect allergy are Adrenaline, Avoidance and Allergist.) 

    Beef tapeworm: Taenia saginata, the most common of the big tapeworms that parasitizes people, contracted from infected raw or rare beef. Can grow to be 12-25 feet (3.6-7.5 m) long in the human intestine. Also known as the African tapeworm. 

    Behcet’s syndrome: Behcet’s syndrome is classically characterized as a triad of symptoms that include recurring crops of mouth ulcers (called apthous ulcers), genital ulcers, and inflammation of a specialized area around the pupil of the eye, the uvea. (The inflammation is called uveitis.) The cause of Behcet’s syndrome is not known. The disease is more frequent and severe in patients from the Eastern Mediterranean and Asia than those of European descent. 

    Belching: A normal process to relieve distention from the air that accumulates in the stomach. The upper abdominal discomfort associated with excessive swallowed air may extend into the lower chest, producing symptoms suggesting heart or lung disease. 

    Belly button: The navel or umbilicus. The one-time site of attachment of the umbilical cord. The term "belly button" was coined around 1877. 

    Benign: Not cancer; does not invade surrounding tissue or spread to other parts of the body. 

    Benign prostatic hypertrophy (BPH): Nonmalignant (noncancerous) enlargement of the prostate gland, a common occurrence in older adult men. 

    Bernard syndrome: A complex of abnormal findings, namely sinking in of one eyeball, ipsilateral ptosis (drooping of the upper eyelid on the same side) and miosis (constriction of the pupil of that eye) together with anhidosis (lack of sweating) and flushing of the affected side of the face. Due to paralysis of certain nerves (specifically, the cervical sympathetic nerves). Also called Horner-Bernard syndrome, Bernard-Horner syndrome and Horner’s ptosis, but best known today as Horner syndrome. 

    Beta blockers: A class of drugs that block the action of adrenaline (a beta adrenergic substance) and can relieve stress to the heart muscle. Beta blockers are often used to slow the heart rate or lower the blood pressure. 

    Beta carotene: An antioxidant which protects cells against oxidation damage that can lead to cancer. Beta carotene is converted, as needed, to vitamin A. Food sources of beta carotene include vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables; and fruit such as cantaloupes and apricots. Excessive carotene in the diet can temporarily yellow the skin, a condition called carotenemia, commonly seen in infants fed largely mushed carrots. 

    Beta error: The statistical error (said to be "of the second kind" or type II) made in testing when it is concluded that something is negative when it really is positive. Beta error is often referred to as a false negative. 

    Bias: In a clinical trial, bias refers to effects that a conclusion that may be incorrect as, for example, when a researcher or patient knows what treatment is being given. To avoid bias, a blinded study may be done. 

    Bicornuate: Having two horns or horn-shaped branches. The uterus (normally unicornuate) can sometimes be bicornuate (with two branches, eg, one at about 10:30 and the other at about 1:30).

    Bifid: Cleft (split) in two. See, for example, bifid uvula. 

    Bifid uvula: The uvula, the little V-shaped fleshy mass hanging from the back of the soft palate, is cleft or split. Cleft uvula is a common minor anomaly occurring in about 1% of whites and 10% of Native Americans. Persons with a cleft uvula should not have their adenoids removed because, without the adenoids, they cannot achieve proper closure between the soft palate and pharynx while speaking and develop hypernasal speech. 

    Bile: A yellow-green fluid made by the liver. Bile is stored in the gallbladder. It passes through the common bile duct into the duodenum, where it helps digest fat. 

    Bilharzia: Disease caused by worms that parasitize people. Also called schistosomiasis.. Three main species of these trematode worms (flukes)--Schistosoma haematobium, S. japonicum, and S. mansoni—cause disease in humans. Larval forms of the parasite live in freshwater snails. The cercaria (form of the parasite) is liberated from the snail burrow into skin, transforms to the schistosomulum stage, and migrates to the urinary tract (S. haematobium), liver or intestine (S. japonicum, S.mansoni) where the adult worms develop. Eggs are shed into the urinary tract or the intestine and hatch to form miracidia (yet another form of the parasite) which then infect snails, completing the life cycle of the parasite.. Adult schistosome worms can seriously damage tissue. The name bilharzia comes from that of the shortlived German physician Theodor Bilharz (1825-1862). 

    Bilharziasis: a parasite infection by a trematode worm acquired from infested water. Also known as schistosomiasis. Species which live in man can produce liver, bladder, and gastrointestinal problems. Species of the schistosomiasis parasite which cannot live in man cause swimmer’s itch. 

    Bilirubin: A yellow-orange compound produced by the breakdown of hemoglobin from red blood cells. 

    Biologic evolution: Biologic evolution was contrasted with cultural evolution in 1968 by A.G. Motulsky who pointed out that biologic evolution is mediated by genes, shows a slow rate of change, employs random variation (mutations) and selection as agents of change, new variants are often harmful, these new variants are transmitted from parents to offspring, the mode of transmission is simple, complexity is achieved by the rare formation of new genes by chromosome duplication, biologic evolution occurs with all forms of life, and the biology of humans requires cultural evolution. See Cultural evolution. 

    Biological response modifiers: Substances that stimulate the body's response to infection and disease. The body naturally produces small amounts of these substances. Scientists can produce some of them in the laboratory in large amounts and use them in cancer treatment. Also called BRMs. 

    Biological therapy: Treatment to stimulate or restore the ability of the immune (defense) system to fight infection and disease. Also called immunotherapy. 



    Biopsy: The removal of a sample of tissue for examination under a microscope to check for cancer cells. A specialist trained to examine such tissues is called a pathologist. 

    Biotechnology: The fusion of biology and technology. Biotechnology is the application of biological techniques to product research and development. In particular, biotechnology involves the use by industry of recombinant DNA, cell fusion, and new bioprocessing techniques. Biotechnology is expected to become increasingly important in the 21st century. 

    Bipolar disease: A type of depressive disease, formerly called manic-depressive illness. Not nearly as prevalent as other forms of depressive disorders, bipolar disorder involves cycles of depression and elation or mania. Sometimes the mood switches are dramatic and rapid, but most often they are gradual. Mania often affects thinking, judgment, and social behavior in ways that cause serious problems and embarrassment. For example, unwise business or financial decisions may be made when an individual is in a manic phase. Bipolar disorder is often a chronic recurring condition. 

    Birth rate: The birth rate is usually given as the number of live births divided by the average population (or the population at midyear). This is termed the crude birth rate. In 1995, for example, the crude birth rate per 1,000 population was 14 in the United States, 16.9 in Australia, etc. 

    Black death: The black plague, i.e., the plague. In 14th-century Europe, the victims of the "black plague" had bleeding below the skin (subcutaneous hemorrhage) which made darkened ("blackened") their bodies. Black plague can lead to "black death" characterized by gangrene of the fingers, toes, and nose. Black plague is caused by a bacterium (Yersinia pestis) which is transmitted to humans from infected rats by the oriental rat flea. 

    Black plague: In 14th-century Europe, the victims of the "black plague" had bleeding below the skin (subcutaneous hemorrhage) which made darkened ("blackened") their bodies. Black plague can lead to "black death" characterized by gangrene of the fingers, toes, and nose. Black plague is caused by a bacterium (Yersinia pestis) which is transmitted to humans from infected rats by the oriental rat flea. 

    Bladder: The organ that stores urine. 

    Bladder cancer: The most common warning sign of bladder cancer is blood in the urine. The diagnosis of bladder cancer is supported by findings in the medical history and examination, blood, urine, and x-ray tests, and confirmed with a biopsy (usually during a cystoscope exam). Treatment of bladder cancer depends on the growth, size, and location of the tumor. 

    Bladder cancer risks: Smoking is a major risk factor. Cigarette smokers develop bladder cancer 2-3 times more often than do nonsmokers. Quitting smoking reduces the risk of bladder cancer, lung cancer, several other types of cancer, and a number of other diseases as well. Workers in some occupations are at higher risk of developing bladder cancer because of exposure to carcinogens (cancer-causing substances) in the workplace. These workers include people in the rubber, chemical, and leather industries, as well as hairstylists, machinists, metal workers, printers, painters, textile workers, and truck drivers. 

    Bladder infection: Some people are at more risk for bladder and other urinary tract infections (UTIs) than others. One woman in five develops a UTI during her lifetime. Not everyone with a UTI has symptoms. Common symptoms include a frequent urge to urinate and a painful, burning when urinating. Underlying conditions that impair the normal urinary flow can lead to more complicated UTIs. 

    Bladder inflammation: Also referred to as cystitis. Cystitis most commonly occurs because of bacterial infection. Another form of bladder inflammation, interstitial cystitis (IC) involves inflammation or irritation of the bladder wall. This can lead to scarring and stiffening of the bladder, and even ulcerations and bleeding. Diagnosis is based on symptoms, findings on cystoscopy and biopsy, and eliminating other treatable causes such as infection. Because doctors do not know what causes IC, treatments are aimed at relieving symptoms. Most people are helped for variable periods of time by one or a combination of treatments. 

    Bladder pain: Among the symptoms of bladder infection are feelings of pain, pressure and tenderness around the bladder, pelvis, and perineum (the area between the anus and vagina or anus and scrotum), which may increase as the bladder fills and decrease as it empties; decreased bladder capacity; an urgent need to urinate; painful sexual intercourse; and, in men, discomfort or pain in the penis and scrotum. 

    Blast phase: Refers to advanced chronic myelogenous leukemia. In this phase, the number of immature, abnormal white blood cells in the bone marrow and blood is extremely high. Also called blast crisis. 

    Blasts: Immature blood cells. 

    Bleb: A bladderlike structure more than 5 mm in diameter with thin walls that may be full of fluid. Also called a bulla. 

    Blepharospasm: The involuntary, forcible closure of the eyelids. The first symptoms may be uncontrollable blinking. Only one eye may be affected initially, but eventually both eyes are usually involved. The spasms may leave the eyelids completely closed causing functional blindness even though the eyes and vision are normal. Blepharospasm is a form of focal dystonia. 

    Blinded study: Clinical trials of drugs are often done blinded so that the patient does not know (is blinded as to) whether they are receiving the product being tested or the control/placebo to ensure that the results of a study are not affected by a possible placebo effect (by the power of suggestion). 

    Blood: The blood is the fluid in the body that contains red and white cells as well as platelets, proteins, plasma and other elements. It is transported throughout the body by the circulatory system. 

    Blood-brain barrier: A protective network of blood vessels and cells that filters blood flowing to the brain. 

    Blood group: An inherited feature on the surface of the red blood cell. A series of related blood groups make up a blood group system such as the ABO system or the Rh system. 

    Blood pressure: The blood pressure is the pressure of the blood within the arteries. It is produced primarily by the contraction of the heart muscle. It's measurement is recorded by two numbers. The first (systolic pressure) is measured after the heart contracts and is highest. The second (diastolic pressure) is measured before the heart contracts and lowest. A blood pressure cuff is used to measure the pressure. Elevation of blood pressure is called "hypertension." (see hypertension). 

    Blood pressure, high: High blood pressure (hypertension) is a repeatedly elevated blood pressure exceeding 140 over 90 mmHg. High blood pressure is also called "the silent killer." Chronically high blood pressure can cause blood vessel changes in the back of the eye (retina), thickening of the heart muscle, kidney failure, and brain damage. No specific cause for high blood pressure is found in 95% of patients. High blood pressure is treated with salt restriction, regular aerobic exercise, and medications. 

    Blood sugar, low: The sugar here is glucose. Low blood glucose constitutes hypoglycemia . Hypoglycemia is only significant when it is associated with symptoms. It has many causes including drugs, liver disease, surgical absence of the stomach, pre-diabetes, and rare tumors that release excess insulin. 

    Blood sugar, high: Elevated levels of blood glucose (hyperglycemia) can be found in a number of conditions. The hyperglycemia leads to spillage of glucose into the urine, hence the term sweet urine. (Diabetes mellitus means "sweet urine.") 

    Blood-thinner: An anticoagulant. 

    Blood transfusion: The transfer of blood or blood products from one person (donor) into another person’s bloodstream (recipient). In most situations this is done as a life saving maneuver to replace blood cells or blood products lost through severe bleeding. Transfusion of your own blood (autologous) is the safest method but requires planning ahead and not all patients are eligible. Directed donor blood allows the patient to receive blood from known donors. Volunteer donor blood is usually readily available and when properly tested has a low incidence of adverse events. Blood conserving techniques are an important aspect of limiting transfusion requirements. 



    Blood urea nitrogen (BUN): A measure primarily of the urea level in blood. Urea is cleared by the kidney. Diseases that compromise the function of the kidney frequently lead to increased blood levels. 

    Blood, urinary: Medically called hematuria, blood in the urine can be microscopic or gross. Evaluating hematuria requires consideration of the entire urinary tract. Tests used for the diagnosis of hematuria include the intravenous pyelogram (IVP), cystoscopy, and urine cytology. Management of hematuria depends upon the underlying cause. 

    Bloody show: Literally, the appearance of blood. The bloody show consists of blood-tinged mucus created by extrusion and passage of the mucous plug that filled the cervical canal (the canal between the vagina and uterus) during pregnancy. The bloody show is therefore a classic sign of impending labor. The same term, bloody show, can be applied to the beginning of menstruation. 

    Blot, Northern: A technique in molecular biology, used mainly to separate and identify pieces of RNA. Called a Northern blot only because it is similar to a Southern blot (which is named after its inventor, the British biologist M.E. Southern). 

    Blot, Southern: A common test for checking for a match between DNA molecules. DNA fragments are separated by agarose gel electrophoresis, transferred (blotted) onto membrane filters, and hybridized with complementary radiolabeled probes. The aim is to detect specific base sequenceswith the probes. Lest all of this sound esoteric, note that in the television series "The X Files" a Southern blot was done (in this case, to learn if some alien virus genome had been integrated into a person’s genome). The Southern blot is named after its inventor, the British biologist M.E. Southern. There is also a Northern blot and a Western blot. 

    Blot, Western: A technique in molecular biology, used to separate and identify proteins. Called a Western blot merely because it has some similarity to a Southern blot (which is named after its inventor, the British biologist M.E. Southern). 

    Boils: A skin abscess, a collection of pus that forms inside the body. Antibiotics are often not very helpful in treating abscesses. The main treatments include hot packs and draining ("lancing") the abscess, but only when it is soft and ready to drain. If you have a fever or long-term illness, such as cancer or diabetes, or are taking medications that suppress the immune system, you should contact your healthcare practitioner if you develop an abscess. 

    Bone: Bone is the substance that forms the skeleton of the body. It is composed chiefly of calcium phosphate and calcium carbonate. It also serves as a storage area for calcium, playing a large role in calcium balance in the blood. 

    Bone cancer: Cancers that begin in bone are rare but it is not unusual for cancers to spread to bone from other parts of the body. This is not called bone cancer, but is named for the organ or tissue in which the cancer begins. Pain is the most frequent symptom of cancer of the bone. Diagnosis of cancer of the bone is supported by findings of the medical history and examination, blood and x-ray tests and confirmed with a biopsy. Treatment of cancer of the bone depends on the type, location, size, and extent of the tumor as well as the age and health of the patient. 

    Bone density: Bone density is the amount of bone tissue in a certain volume of bone. It can be measured using a special x-ray called a quantitative computed tomogram. 

    Bone marrow: The bone marrow is the soft substance that fills bone cavities. It is composed of mature and immature blood cells and fat. The blood cells include white blood cells, red blood cells and platelets. Diseases or drugs that affect the bone marrow can affect the "total counts" of these cells. 

    Bone marrow aspiration: The removal of a small sample of bone marrow (usually from the hip) through a needle for examination under a microscope to see whether cancer cells are present. 

    Bone marrow biopsy: The removal of a small piece of bone and bone marrow (usually from the hip) through a large needle. The sample is examined under a microscope to see whether cancer cells are present. 

    Bone marrow transplantation: A procedure in which doctors replace diseased bone marrow with healthy bone marrow. The diseased bone marrow is destroyed by high doses of chemotherapy and/or radiation therapy. The replacement marrow may come from another person, or it may be the patient's own marrow (which was removed and stored before treatment). When donated marrow is used, the procedure is usually called allogeneic bone marrow transplantation. Autologous bone marrow transplantation uses the patient's own marrow. 

    Bone scan: A technique to create images on bones on a computer screen or on film. A small amount of radioactive material is injected and travels through the bloodstream. It collects in the bones, especially in abnormal areas of the bones, and is detected by a scanner. 

    Boutonneuse: Fièvre boutonneuse or African tick typhus, one of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (tache noire) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash. The French word "boutonneuse" means pimply. Also called Conor and Bruch’s disease. 

    Bowel: Another name for the intestine. There is both a small and a large bowel. 

    Bowel disorders and fiber: High fiber diets help delay the progression of diverticulosis and, at least, reduce the bouts of diverticulitis. In many cases, it helps reduce the symptoms of the Irritable Bowel Syndrome ( IBS ). It is generally accepted that a diet high in fiber is protective, or at least reduces the incidence, of colon polyps and colon cancer. 



    bp: In genetics, base pair. In general medicine, blood pressure (but usually in capital letters as BP). 

    BP: Commonly used abbreviation for blood pressure. For example, in a medical chart, you might see scrawled "BP90/60 T98.6 Ht60/reg R15", which is short hand signifying that the blood pressure is 90/60 mm Hg, the temperature (T) is 98.6 degrees Fahrenheit, the heart rate (Ht) is 60 beats/min and regular, and the respirations ® 15/min. (This would be entirely normal for an adult or older child). 

    BPH: Benign prostatic hypertrophy. Nonmalignant enlargement of the prostate gland. 

    Brachial plexus: A bundle of nerves beginning in the posterior base of the neck and extending through the axilla. I is formed by the union of portions of the fifth through eighth cervical spinal nerves and first thoracic spinal nerve. Damage to the brachial plexus can affect nerves supplying the arm and chest. 

    Bradycardia: A slow heart rate, usually defined as less than 60 beats per minute. 

    Brain: The brain is that portion of the central nervous system that is located within the skull. It functions as a primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres." 

    Brain stem: The stemlike part of the brain that is connected to the spinal cord. 

    Brain stem glioma: A type of brain tumor. 

    Brain tumors: Can be malignant or benign and can occur at any age. Primary brain tumors initially form in the brain tissue. Secondary brain tumors are cancers that have spread to the brain tissue (metastasized) from tissue elsewhere in the body. 

    Branchial cleft cyst: Also called a branchial cyst, this is a cavity that is a remnant from embryologic development present at birth in one side of the neck just in front of the large angulated muscle on either side (the sternocleidomastoid muscle). The cyst may not be recognized until adolescence as it enlarges its oval shape. Sometimes it develops a sinus or drainage pathway to the surface of the skin from which mucus can be expressed. Total surgical excision is the treatment of choice. Recurrence is not expected. 

    Branchial cyst: Also called a branchial cleft cyst, this is a cavity that is a remnant from embryologic development present at birth in one side of the neck just in front of the large angulated muscle on either side (the sternocleidomastoid muscle). The cyst may not be recognized until adolescence as it enlarges its oval shape. It may develop a sinus or drainage pathway to the surface of the skin from which mucus can be expressed. Total surgical excision is the treatment of choice. Recurrence is not expected. 

    BRCA1: A gene that normally acts to restrain the growth of cells. (The symbol BRCA comes from BReast CAncer). 

    BRCA1 breast cancer susceptibility gene: This mutated (changed) version of the BRCA1 gene makes a person susceptible to developing breast cancer. 

    Breast: The anterior aspect of the chest or the mammary gland. The latter is composed of primarily fat in which there is a complex branching duct network from the nipple inward. In the female, lobules develop at the end of the ducts to produce milk. 

    Breast augmentation: Enlargement of the breasts. Augmentation of the breast typically consists of insertion of a silicone bag (prosthesis) under the breast (submammary) or under the breast and chest muscle (subpectoral) and then filling the bag with saline (salt water). This prosthesis expands the breast area to give a fuller breast (increased cup size), give a better contour, and give better cleavage. 

    Breast cancer: Breast cancer is diagnosed with self- and physician-examination of the breasts, mammography, ultrasound testing, and biopsy. There are many types of breast cancer that differ in their capability of spreading to other body tissues (metastasis). Treatment of breast cancer depends on the type and location of the breast cancer, as well as the age and health of the patient. The American Cancer Society recommends that a woman should have a baseline mammogram between the ages of 35 and 40 years. Between 40 and 50 years of age mammograms are recommended every other year. After age 50 years, yearly mammograms are recommended. 

    Breast cancer, familial: A number of factors have been identified that increase the risk of breast cancer. One of the strongest of these risk factors is the history of breast cancer in a relative. About15-20% of women with breast cancer have such a family history of the disease, clearly reflecting the participation of inherited (genetic) components in the development of some breast cancers. Dominant breast cancer suceptibility genes, including BRCA1 and BRCA2, appear responsible for about 5% of all breast cancer. See related entries to: Breast cancer susceptibility genes; BRCA1; BRCA2. 

    Breast cancer susceptibility genes: Inherited factors that predispose to breast cancer. Put otherwise, these genes make one more susceptible to the disease and so increase the risk of developing breast cancer. Two of these genes, BRCA1 and BRCA2, have been identified (and prominently publicized). Several other genes (those for the Li-Fraumeni syndrome, Cowden disease, Muir-Torre syndrome, and ataxia-telangiectasia) are also known to predispose to breast cancer. However, since all of these known breast cancer susceptibility genes together do not account for more than a minor fraction (1/5th at most) of breast cancer that clusters in families, it is clear that more breast cancer genes remain to be discovered. 

    Breast feeding: The ability of the breast to produce milk diminishes soon after childbirth without the stimulation of breastfeeding. Immunity factors in breast milk can help the baby to fight off infections. Breast milk contains vitamins, minerals, and enzymes which aid the baby’s digestion. Breast and formula feeding can be used together. 

    Breech: The buttocks. 

    Breech delivery: Literally, delivery of the baby by the buttocks first (as opposed to the head. The "Good Word" according to The Florida Times-Union of Feb. 10, 1998 is "Breech delivery—Birth, feet first." This is, of course, wrong. It should be: "Breech delivery—Birth, buttocks first." 

    Bridge teeth are false teeth that replace on or more missing teeth supported by a metal framework. 

    Brill-Zinsser disease: Recrudescence of epidemic typhus years after the initial attack. The agent that causes epidemic typhus (Rickettsia prowazekii) remains viable for many years and then when host defenses are down, it is reactivated causing recurrent typhus. The disease is named for the physician Nathan Brill and the great bacteriologist Hans Zinsser. 



    Bronchi: The large air tubes which begin at the end of the trachea and branch into the lungs. Characterized by having cartilage as part of the supporting wall structure. 

    Bronchioles: The tiny branches of air tubes within the lungs which are the continuation of bronchi and connect to the alveoli (air sacs). 

    Bronchitis: Inflammation (swelling and reddening) of the bronchi. 

    Bronchopulmonary segments: A subdivision of one lobe of a lung based on the connection to the segmental bronchus. For example, the right upper lobe has apical, anterior, and posterior segments. 

    Bronchoscope: A thin, flexible instrument used to view the air passages of the lung. 

    Bronchoscopy: A test that permits the doctor to see the breathing passages through a lighted tube. 

    Brown’s syndrome: An ophthalmology (eye) problem. Brown’s syndrome presents as an abnormality at birth (congenitally) and is characterized by an inability to elevate the eyeball when also trying to move the eyeball to the outside. Brown’s syndrome can also occur because of other conditions which affect the normal function of the eye muscles. 

    Bruise: A bruise or "contusion" is an traumatic injury of the soft tissues which results in breakage of the local capillaries and leakage of red blood cells. In the skin it can be seen as a reddish-purple discoloration which does not blanch when pressed upon. When it fades it becomes green and brown as the body metabolizes the blood cells in the skin. It is best treated with local application of a cold pack immediately after injury. 

    Bubo: An enlarged lymph node ("swollen gland") that is tender and painful, particularly in the groin and armpit (the axilla). A feature of a number of infectious diseases including gonorrhea, syphilis, tuberculosis, and the plague. Hence, the bubonic plague. The odd word "bubo" comes from the Greek "boubon" meaning groin or swollen groin. 

    Buboes: The plural of "bubo". 



    Bubonic plague: The most common form of the plague named for the characteristic buboes which are enlarged lymph nodes ("swollen glands") in the groin that are tender and painful. Lymph nodes may be similarly affected in the armpits (axillae), neck and elsewhere. Other features of the bubonic plague include headache, fever, chills, and weakness. Bubonic plague is caused by a bacterium (Yersinia pestis) which is transmitted to humans from infected rats by the oriental rat flea. Bubonic plague can lead to "black death" characterized by gangrene of the fingers, toes, and nose. 

    Buccal mucosa: The inner lining of the cheeks and lips. 

    Bulimia: An insatiable appetite, often interrupted by periods of anorexia. Bulimia is a psychological disorder that can be accompanied by self-induced vomiting. 

    Bulla: A blister more than 5 mm in diameter with thin walls that is full of fluid. Also called a bleb. 

    Bullous: Characterized by blistering, such as in second-degree burn. 

    Bullous pemphiguoid: A disease characterized by tense blistering eruptions of the skin. caused by antibodies abnormally accumulating in a layer of the skin called the "basement membrane." Can be chronic and mild without affecting the general health. It is diagnosed by skin biopsy showing the abnormal antibodies deposited in the skin layer. Treatment is with topical cortisone creams, but sometimes requires high doses of cortisone ("steroids") taken internally. 

    Bumps: The raised area of a bump or bruise results from blood leaking from these injured blood vessels into the tissues as well as from the body’s response to the injury. A purplish, flat bruise that occurs when blood leaks out into the top layers of skin is referred to as an ecchymosis. 

    BUN: Blood urea nitrogen. A measure primarily of the urea level in blood. Urea is cleared by the kidney and diseases which compromises the function of the kidney will frequently lead to increased blood levels. 

    Bunion: A bunion is a localized painful swelling at the base of the big toe. It is frequently associated with inflammation. It can be related to inflammation of the nearby bursa (bursitis) or degenerative joint disease (osteoarthritis). 

    Burkitt's lymphoma: A type of non-Hodgkin's lymphoma that most often occurs in young people between the ages of 12 and 30. The disease usually causes a rapidly growing tumor in the abdomen. 

    Burns: The treatment of burns depends on the depth, area and location of the burn. Burn depth is generally categorized as first, second or third degree. A first degree burn is superficial and has similar characteristics to a typical sun burn. The skin is red in color and sensation is intact. In fact, it is usually somewhat painful. Second degree burns look similar to the first degree burns; however, the damage is now severe enough to c ause blistering of the skin and the pain is usually somewhat more intense. In third degree burns the damage has progressed to the point of skin death. The skin is white and without sensation. 

    Burns, first degree: A first degree burn is superficial and has similar characteristics to a typical sun burn. The skin is red in color and sensation is intact. In fact, it is usually somewhat painful. 



    Burns, second degree: Second degree burns look similar to the first degree burns in that it is red and sensation is intact; however, the damage is severe enough to cause blistering of the skin and the pain is usually somewhat more intense. 

    Burns, third degree: In third degree burns the damage has progressed to the point of skin death. The skin is white and without sensation. 

    Bursa: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known to as "bursitis." Most commonly this is not an infectious condition (aseptic bursitis). When the bursa is infected with bacteria, the condition is called septic bursitis. Bypass: An operation in which the surgeon creates a new pathway for the movement of substances in the body. 

    Bursitis: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known to as "bursitis." 

    Bursitis, aseptic: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known as "bursitis." Most commonly this is not an infectious condition (aseptic bursitis). 

    Bursitiis, calcific: A bursa is a thin fluid-filled sac that reduces friction forces between tissues of the body. Chronic (repeated of long-standing) inflammation of the bursa (bursitis) can lead to calcification of the bursa. This is referred to as "calcific bursitis." The calcium deposition (calcification) can occur as long as the inflammation is present. 

    Bursitis, elbow: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. The bursa at the tip of the elbow is called the olecranon bursa. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery. 

    Bursitis, hip: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are two major bursae of the hip. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery. 

    Bursitis, knee: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are three major bursae of the knee. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery. 

    Bursitis, septic: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known as "bursitis." When the bursa is infected with bacteria, the condition is called septic bursitis. 

    Bursitis, shoulder: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are two major bursae of the shoulder. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery. 

    Bypass (Coronary Artery Bypass Graft): Coronary artery disease develops because of hardening of the arteries (atherosclerosis) that supply blood to the heart muscle. Diagnostic tests include EKG, stress test, echocardiography, and coronary angiography. Coronary artery bypass graft (CABG) surgery is advised for selected groups of patients with significant narrowings and blockages of the heart arteries (coronary artery disease) to create new routes around narrowed and blocked arteries, permitting increased blood flow to deliver oxygen and nutrients to the heart muscles. The bypass graft for a CABG can be a vein from the leg or an inner chest wall artery. CABG surgery is performed about 350,000 times annually in the United States, making it one of the most commonly performed major operations. 

    Bypass, cardiopulmonary: Bypass of the heart and lungs as, for example, in open heart surgery. Blood returning to the heart is diverted through a heart-lung machine (a pump-oxygenator) before returning it to the arterial circulation. The machine does the work both of the heart (pump blood) and the lungs (supply red blood cells with oxygen).

  • C: Cystosine, one member of the G-C (guanine-cytosine) pair of bases in DNA.
    C-section: Short for Caesarian section.
    C/S: Abbreviation for Caesarian section. Why the slash (/) is between the "C" and the "S", who knows?
    CABG (Coronary Artery Bypass Graft): Coronary artery disease develops because of hardening of the arteries (atherosclerosis) that supply blood to the heart muscle. Diagnostic tests include EKG, stress test, echocardiography, and coronary angiography. CABG surgery is advised for selected groups of patients with significant narrowings and blockages of the heart arteries (coronary artery disease) to create new routes around narrowed and blocked arteries, permitting increased blood flow to deliver oxygen and nutrients to the heart muscles. The bypass graft for a CABG can be a vein from the leg or an inner chest wall artery. CABG surgery is performed about 350,000 times annually in the United States, making it one of the most commonly performed major operations.
    Caesarian section: Procedure in which an infant, rather than being born vaginally, is surgically removed from the uterus. Also referred to as a C section. As the name "Caesarian" suggests, this is not exactly a new procedure. It was done in ancient civilizations upon the death of a near-full-term pregnant woman to salvage the baby. Julius Caesar (or one of his predecessors) was born by this procedure. Hence, the name "Caesarian". The term "section" in surgery refers to the division of tissue. What is being divided here is the abdominal wall of the mother as well as the wall of the uterus in order to extract the baby. In Shakespeare’s "Macbeth" the Witches’ prophecy was that "...none of woman born/ Shall harm Macbeth" (IV.i). Unfortunately for Macbeth, the Scottish nobleman Macduff was "from his mother’s womb/ Untimely ripped." and thus not naturally "born of woman"(V.vii). Macduff was the only agent capable of destroying Macbeth. He killed Macbeth in battle.
    Calcific bursitis: A bursa is a thin fluid-filled sac that reduces friction forces between tissues of the body. Chronic (repeated of long-standing) inflammation of the bursa (bursitis) can lead to calcification of the bursa. This is referred to as "calcific bursitis." The calcium deposition (calcification) can occur as long as the inflammation is present.
    Calcium: A mineral found mainly in the hard part of bones. Bone is a storage area for calcium. Calcium is added to bone by cells called osteoblasts. It is removed from bone by cells called osteoclasts. Calcium is not just essential for healthy bones. It is also important for muscle contraction, heart action and normal blood clotting. A low blood calcium (hypocalcemia) makes the nervous system highly irritable with tetany (spasms of the hands and feet, muscle cramps, abdominal cramps, overly active reflexes, etc.). Chronic calcium deficiency contributes to poor mineralization of bones, soft bones (osteomalacia) and osteoporosis; and, in children, rickets and impaired growth. Food sources of calcium include dairy foods, some leafy green vegetables such as broccoli and collards, canned salmon, clams, oysters, calcium-fortified foods, and tofu. According to the National Academy of Sciences, adequate intake of calcium is 1 gram daily for both men and women. The upper limit for calcium intake is 2.5 grams daily. Overly high intake of calcium (hypercalcemia) may cause muscle weakness and constipation, affect the conduction of electrical impulses in the heart (heart block) lead to calcium stones (nephrocalcinosis) in the urinary tract, impair kidney function, and interfere with the absorption of iron predisposing to iron deficiency.
    Calcium deficiency: A low blood calcium (hypocalcemia) makes the nervous system highly irritable with tetany (spasms of the hands and feet, muscle cramps, abdominal cramps, overly active reflexes, etc.). Chronic calcium deficiency contributes to poor mineralization of bones, soft bones (osteomalacia) and osteoporosis; and, in children, rickets and impaired growth. Food sources of calcium include dairy foods, some leafy green vegetables such as broccoli and collards, canned salmon, clams, oysters, calcium-fortified foods, and tofu. According to the National Academy of Sciences, adequate intake of calcium is 1 gram daily for both men and women. The upper limit for calcium intake is 2.5 grams daily.
    Calcium excess: Overly high intake of calcium (hypercalcemia) may cause muscle weakness and constipation, affect the conduction of electrical impulses in the heart (heart block) lead to calcium stones in the urinary tract, impair kidney function (through nephrocalcinosis), and interfere with the absorption of iron predisposing to iron deficiency. According to the National Academy of Sciences, adequate intake of calcium is 1 gram daily for both men and women. The upper limit for calcium intake is 2.5 grams daily.
    Callus: (1) A callus or callosity is a localized firm thickening of the upper layer of skin as a result of repetitive friction. (2) A callus is the hard new bone substance that forms in an area of bone fracture. It is part of the bone repair process.
    Cancer: Also called malignancy. Cancer refers to a abnormal growths which have a tendency to grow uncontrolled and metastasize. It can involve any tissue of the body and can have many different forms in each body area. Cancer is a group of more than 100 different diseases. Benign tumors are not cancer; malignant tumors are cancer. Most cancers are named for the type of cell or the organ in which they begin. When cancer spreads (metastasizes), the new tumor has the same name as the original (primary) tumor. Skin cancer is the most common type of cancer for both men and women. The second most common cancer in men is prostate cancer, in women it is breast cancer. Lung cancer is the leading cause of death from cancer for both men and women in the U.S. Cancer is NOT contagious.
    Cancer, bladder: Cancer of the organ responsible for temporarily holding urine after it leaves the kidneys. The most common warning sign of cancer in the bladder (the hollow organ in the lower abdomen that stores urine) is blood in the urine. The diagnosis of bladder cancer is supported by findings of the medical history and examination, blood, urine, and x-ray tests, and confirmed with a biopsy (usually during a cystoscope exam).
    Cancer, bone: Cancer of the skeleton. Cancers that begin in bone are rare but it is not unusual for cancers to spread (metastasize) to bone from other parts of the body. This is not called bone cancer, but is named for the organ or tissue in which the cancer begins. Pain is the most frequent symptom of cancer of the bone. Diagnosis of cancer of the bone is supported by findings of the medical history and examination, blood and x-ray tests and confirmed with a biopsy.
    Cancer, brain: Cancer of the central information processing center of the body. Tumors in the brain can be malignant or benign and can occur at any age. Primary brain tumors initially form in the brain tissue. Secondary brain tumors are cancers that have spread to the brain tissue (metastasized) from elsewhere in the body.
    Cancer, breast: Cancer of the tissue containing or involving the milk glands (mammary tissue). Breast cancer is diagnosed with self- and physician- examination of the breasts, mammography, ultrasound testing, and biopsy. There are many types of breast cancer that differ in their capability of spreading to other body tissues (metastasis). Treatment of breast cancer depends on the type and location of the breast cancer, as well as the age and health of the patient. The American Cancer Society recommends that a woman should have a baseline mammogram between the ages of 35 and 40 years. Between 40 and 50 years of age mammograms are recommended every other year. After age 50 years, yearly mammograms are recommended.
    Cancer, causes: Cancer is a group of more than 100 different diseases. Benign tumors are not cancer; malignant tumors are cancer. Most cancers are named for the type of cell or the organ in which they begin. When cancer spreads (metastasizes), the new tumor has the same name as the original (primary) tumor. Skin cancer is the most common type of cancer for both men and women. The second most common cancer in men is prostate cancer, in women it is breast cancer. Lung cancer is the leading cause of death from cancer for both men and women in the U.S. Cancer is NOT contagious.
    Cancer, cervix: Cancer of the entrance to the womb (uterus). Regular pelvic exams and Pap testing can detect precancerous changes in the cervix. Precancerous changes in the cervix may be treated with cryosurgery, cauterization, or laser surgery. The most common symptom of cancer of the cervix is abnormal bleeding. Cancer of the cervix can be diagnosed using a Pap test or other procedures that sample the cervix tissue. Cancer of the cervix requires different treatment than cancer that begins in other parts of the uterus.
    Cancer, colon: A malignant tumor arising from the inner wall of the large intestine. The third leading cause of cancer in males, fourth in females in the U.S. Risk factors for cancer of the colon and rectum (colorectal cancer) include heredity, colon polyps, and long standing ulcerative colitis. Most colorectal cancers develop from polyps. Removal of colon polyps can prevent colorectal cancer. Colon polyps and early cancer can have no symptoms. Therefore, regular screening is important. Diagnosis can be made by barium enema or by colonoscopy with biopsy confirmation of cancer tissue. Surgery is the most common treatment for colorectal cancer.
    Cancer, colon: screening and surveillance: Colon cancer is both preventable and curable. It is preventable by removing precancerous colon polyps. It is curable if early cancer is surgically removed before cancer spread to other parts of the body. Therefore, if screening and surveillance programs were practiced universally, there would be a major reduction in the incidence and mortality of colon cancer.
    Cancer detection: Methods used to find cancer in persons who may or may not have symptoms. Symptoms of cancer are abnormal sensations or conditions that persons can notice that are a result of the cancer. It is important to your doctor for regular checkups and not wait for problems to occur. But you should also know that the following symptoms may be associated with cancer: changes in bowel or bladder habits, a sore that does not heal, unusual bleeding or discharge, thickening or lump in the breast or any other part of the body, indigestion or difficulty swallowing, obvious change in a wart or mole, or nagging cough or hoarseness. These symptoms are not always a sign of cancer. They can also be caused by less serious conditions. Only a doctor can make a diagnosis. It is important to see a doctor if you have any of these symptoms. Don’t wait to feel pain. Early cancer often does not cause pain.
    Cancer, esophagus: Cancer of the swallowing tube that passes from the throat to the stomach. The risk of cancer of the esophagus is increased by long-term irritation of the esophagus, such as with smoking, heavy alcohol intake, and Barrett’s esophagitis. Cancer of the esophagus can cause difficulty and pain with swallowing solid food. Diagnosis of esophageal cancer can be made by barium x-ray of the esophagus, and confirmed by endoscopy with biopsy of the cancer tissue.
    Cancer, gastric: Cancer of the stomach, the major organ that holds food for digestion. Stomach cancer (gastric cancer) can develop in any part of the stomach and spread to other organs. Stomach ulcers do not appear to increase a person’s risk of developing stomach cancer. Symptoms of stomach cancer are often vague, such as loss of appetite and weight. The cancer is diagnosed with a biopsy of stomach tissue during a procedure called an endoscopy.
    Cancer, Hodgkin’s disease (adult): A type of lymphoma (cancer of the lymphatic system). The most common symptom of Hodgkin’s disease is a painless swelling in the lymph nodes in the neck, underarm, or groin. Hodgkin’s disease is diagnosed when abnormal tissue is detected by a pathologist after a biopsy of an enlarged lymph node. Treatment usually includes radiation therapy or chemotherapy. Regular follow-up examinations are important after treatment for Hodgkin’s disease. Patients treated for Hodgkin’s disease have an increased risk of developing other types of cancer later in life, especially leukemia.
    Cancer, kidney: Cancer of the major organ responsible for the removal from the blood of the toxins of body metabolism—the kidney. Childhood kidney cancer is different from the adult kidney cancer. The most common symptom of kidney cancer is blood in the urine. The diagnosis of kidney cancer is supported by findings of the medical history and examination, blood, urine, and x-ray tests, and confirmed with a biopsy. Kidney cancer is treated with surgery, embolization, radiation therapy, hormone therapy, biological therapy, or chemotherapy.
    Cancer, larynx: Cancer of the voice box. The larynx is the voice box located at the top of the windpipe (trachea). Cancer of the larynx occurs most often in people over the age of 55 years. People who stop smoking can greatly reduce their risk of cancer of the larynx. Painless hoarseness can be a symptom of cancer of the larynx. The larynx can be examined with a viewing tube called a laryngoscope. Cancer of the larynx is usually treated with radiation therapy or surgery. Chemotherapy can also be used for cancers that have spread.
    Cancer, leukemia: Leukemia is a cancer of the white blood cells. Leukemias are grouped by how quickly the disease develops (acute or chronic) as well as by the type of blood cell that is affected. People with leukemia are at significantly increased risk for developing infections, anemia, and bleeding. Diagnosis of leukemia is supported by findings of the medical history and examination, and examining blood under a microscope. Leukemia cells can be detected and further classified with a bone marrow aspiration and/or biopsy. Most patients with leukemia are treated with chemotherapy. Some patients also may have radiation therapy and/or bone marrow transplantation.
    Cancer, lung: Cancer of the major organ of respiration—the lung. Lung cancer kills more men and women than any other form of cancer. Since the majority of lung cancer is diagnosed at a relatively late stage, only 10% of all lung cancer patients are ultimately cured. Eight out of 10 lung cancers are due to tobacco smoke. Lung cancers are classified as either small cell or non-small cell cancers. Persistent cough and bloody sputum can be symptoms of lung cancer. Lung cancer can be diagnosed based on examination of sputum, or tissue examination with biopsy using bronchoscopy, needle through the chest wall, or surgical excision.
    Cancer, lymphoma, Hodgkin’s (adult): A type of lymphoma (cancer of the lymphatic system). The most common symptom of Hodgkin’s disease is a painless swelling in the lymph nodes in the neck, underarm, or groin. Hodgkin’s disease is diagnosed when abnormal tissue is detected by a pathologist after a biopsy of an enlarged lymph node. Treatment usually includes radiation therapy or chemotherapy. Regular follow-up examinations are important after treatment for Hodgkin’s disease. Patients treated for Hodgkin’s disease have an increased risk of developing other types of cancer later in life, especially leukemia.
    Cancer, lymphoma, non-Hodgkin’s: A lymphoma is a cancer that develops in the lymphatic system. The most common symptom of non-Hodgkin’s lymphomas is a painless swelling in the lymph nodes in the neck, underarm, or groin. Non-Hodgkin’s lymphomas are diagnosed with a biopsy of an enlarged lymph node. Follow-up examinations are important after lymphoma treatment. Most relapses occur in the first 2 years after therapy.
    Cancer, malignant melanoma: A skin cancer that begins in cells called melanocytes that can grow together to form benign (not cancerous) moles. A change in size, shape, or color of a mole can be a sign of melanoma. Melanoma can be cured if detected early, before spread (metastasis) to other areas of the body. Diagnosis is confirmed with a biopsy of the abnormal skin. Sun exposure can cause skin damage that can lead to melanoma.
    Cancer, melanoma: A skin cancer that begins in cells called melanocytes that can grow together to form benign (not cancerous) moles. A change in size, shape, or color of a mole can be a sign of melanoma. It can be cured if detected early, before spread (metastasis) to other areas. Diagnosis is confirmed by a biopsy of the abnormal skin. Sun exposure can cause skin damage that can lead to melanoma.
    Cancer, myeloma: A bone marrow cancer involving a type of white blood cell called a plasma (or myeloma) cell. The tumor cells can form a single collection (a plasmacytoma) or many tumors (multiple myeloma). Plasma cells are part of the immune system and make antibodies. Because patients have an excess of identical plasma cells, they have too much of one type of antibody. As myeloma cells increase in number, they damage and weaken the bones, causing pain and often fractures. When bones are damaged, calcium is released into the blood leading to hypercalcemia (too much calcium in the blood) and that causes loss of appetite, nausea, thirst, fatigue, muscle weakness, restlessness, and confusion. Myeloma cells prevent the bone marrow from forming normal plasma cells and other white blood cells important to the immune system so patients may not be able to fight infections. The cancer cells can also prevent the growth of new red blood cells, causing anemia. Excess antibody proteins and calcium may prevent the kidneys from filtering and cleaning the blood properly.
    Cancer, multiple myeloma: A bone marrow cancer involving a type of white blood cell called a plasma (or myeloma) cell. The tumor cells can form a single collection (a plasmacytoma) or many tumors (multiple myeloma). Plasma cells are part of the immune system and make antibodies. Because patients have an excess of identical plasma cells, they have too much of one type of antibody. As myeloma cells increase in number, they damage and weaken the bones, causing pain and often fractures. When bones are damaged, calcium is released into the blood leading to hypercalcemia (excess calcium in the blood) and that causes loss of appetite, nausea, thirst, fatigue, muscle weakness, restlessness, and confusion. Myeloma cells prevent the bone marrow from forming normal plasma cells and other white blood cells important to the immune system so patients may not be able to fight infections. The cancer cells can also prevent the growth of new red blood cells, causing anemia. Excess antibody proteins and calcium may prevent the kidneys from filtering and cleaning the blood properly Cancer, non-Hodgkin’s lymphoma: A lymphoma is a cancer that develops in the lymphatic system. The most common symptom of non-Hodgkin’s lymphomas is a painless swelling in the lymph nodes in the neck, underarm, or groin. Non-Hodgkin’s lymphomas are diagnosed with a biopsy of an enlarged lymph node. Follow-up examinations are important after lymphoma treatment. Most relapses occur in the first 2 years after therapy.
    Cancer, oral: Cancer of the mouth area. A sore in the mouth that does not heal can be a warning sign of oral cancer. A biopsy is the only to know whether as abnormal area in the oral cavity is cancer. Oral cancer is caused by tobacco (smoking and chewing) and alcohol use. Surgery to remove the tumor in the mouth is the usual treatment for patients with oral cancer.
    Cancer, ovarian: Cancer of the egg sac of females (ovary). In women under age 30, most ovarian growths are benign, fluid-filled sacs called cysts. There are several types of ovarian cancer. Symptoms of ovarian cancer can be vague. Detection of ovarian cancer involves physical examination (including pelvic exam), ultrasound, x-ray tests, CA-125 blood test and biopsy of the ovary.
    Cancer, ovary: Cancer of the egg sac of females. Most ovarian growths in women under age 30 are benign, fluid-filled cysts. There are several types of ovarian cancer. Symptoms of ovarian cancer can be vague. Detection of ovarian cancer involves physical examination (including pelvic exam), ultrasound, x-ray tests, CA-125 blood test and biopsy of the ovary.
    Cancer, pancreas: Cancer of the organ which produces many juices that are important for digesting food as well as hormones, such as insulin and glucagon. Pancreatic cancer has been called a "silent" disease because early pancreatic cancer usually does not cause symptoms. If the tumor blocks the common bile duct and bile cannot pass into the digestive system, the skin and whites of the eyes may become yellow, and the urine darker as a result of accumulated bile pigment called bilirubin. This condition is referred to as jaundice.
    Cancer, pancreatic: Cancer of the organ which produces many juices that are important for digesting food as well as hormones, such as insulin and glucagon. Pancreatic cancer has been called a "silent" disease because early pancreatic cancer usually does not cause symptoms. If the tumor blocks the common bile duct and bile cannot pass into the digestive system, the skin and whites of the eyes may become yellow, and the urine darker as a result of accumulated bile pigment called bilirubin. This condition is referred to as jaundice.
    Cancer, prostate: Cancer of the gland that produces some of the components of semen fluid. Prostate cancer is the second leading cause of death of males in the U.S. Prostate cancer is often first detected as a hard nodule during a routine rectal examination. The PSA blood test is a screening test for prostate cancer. Diagnosis of prostate cancer is established when cancer cells are identified in prostate tissue obtained by a biopsy. In some patients, prostate cancer is life threatening. In many others, prostate cancer can exist for years without causing any health problems. Treatment options for prostate cancer include observation, radiation therapy, surgery, hormonal therapy, and chemotherapy.
    Cancer, prostatic: Cancer of the gland (prostate) that produces some of the components of semen fluid. The second leading cause of death of males in the U.S. Prostate cancer is often first detected as a hard nodule during a routine rectal examination. The PSA blood test is a screening test for prostate cancer. Diagnosis of prostate cancer is established when cancer cells are identified in prostate tissue obtained by a biopsy. In some patients, prostate cancer is life threatening. In many others, prostate cancer can exist for years without causing any health problems. Treatment options for prostate cancer include observation, radiation therapy, surgery, hormonal therapy, and chemotherapy.
    Cancer, rectal: A malignant tumor arising from the inner wall of the end (rectum) of the large intestine. The third leading cause of cancer in males, fourth in females in the U.S. Risk factors for cancer of the colon and rectum (colorectal cancer) include heredity, colon polyps, and long standing ulcerative colitis. Most colorectal cancers develop from polyps. Removal of colon polyps can prevent colorectal cancer. Colon polyps and early cancer can have no symptoms. Therefore, regular screening is important. Diagnosis can be made by barium enema or by colonoscopy with biopsy confirmation of cancer tissue. Surgery is the most common treatment for colorectal cancer.
    Cancer, skin: Cancer of the outer surface of the body. The most common cancer in the U.S. There are many types of skin cancer. Ultraviolet light from sunlight is the main cause of skin cancer. Unexplained changes in the appearance of the skin, lasting longer than 2 weeks, should be evaluated by a doctor. The cure rate for skin cancer could be 100% if all skin cancers were brought to a doctor’s attention before they had a chance to spread.
    Cancer, stomach: Cancer of the major organ that holds food for digestion. Stomach cancer (gastric cancer) can develop in any part of the stomach and spread to other organs. Stomach ulcers do not appear to increase a person’s risk of developing stomach cancer. Symptoms of stomach cancer are often vague, such as loss of appetite or weight. The cancer is diagnosed with a biopsy of stomach tissue during a procedure called an endoscopy.
    Cancer symptoms: Abnormal sensations or conditions that persons can notice that are a result of a cancer. It is important to see your doctor for regular checkups and not wait for problems to occur. But you should also know that the following symptoms may be associated with cancer: changes in bowel or bladder habits, a sore that does not heal, unusual bleeding or discharge, thickening or lump in the breast or any other part of the body, indigestion or difficulty swallowing, obvious change in a wart or mole, or nagging cough or hoarseness. These symptoms are not always a sign of cancer. They can also be caused by less serious conditions. Only a doctor can make a diagnosis. It is important to see a doctor if you have any of these symptoms. Don’t wait to feel pain. Early cancer often does not cause pain.
    Cancer, testicles: Cancer of the male sex organ (testicle) that normally produces the hormone testosterone. One of the most common cancers in young men. Most testicular cancers are found by men themselves as a lump in the testicle. The risk of cancer of the testicles is increased in males whose testicles did not move down normally into the scrotum (holding sac for the testicles) during development if the problem is not corrected in early childhood. This condition is referred to as undescended testicles. When a growth in the testicle is detected, cancer is confirmed after surgical removal of the affected testicle (orchiectomy) and examination of the tissue under a microscope. Testicular cancer is almost always curable if it is found early.
    Cancer, testicular: Cancer of the male sex organ (testicle) that normally produces the hormone testosterone. One of the most common cancers in young men. Most testicular cancers are found by men themselves as a lump in the testicle. The risk of cancer of the testicles is increased in males whose testicles did not move down normally into the scrotum (holding sac for the testicles) during development if the problem is not corrected in early childhood. This condition is referred to as undescended testicles. When a growth in the testicle is detected, cancer is confirmed after surgical removal of the affected testicle (orchiectomy) and examination of the tissue under a microscope. Testicular cancer is almost always curable if it is found early.
    Cancer, thyroid: Cancer of the gland in front of the neck that normally produces thyroid hormone which is important to the normal regulation of the metabolism of the body. There are four major types of cancer of the thyroid gland. Persons who received radiation to the head or neck in childhood should be examined by a doctor every 1 to 2 years. The most common symptom of thyroid cancer is a lump, or nodule, that can be felt in the neck. The only certain way to tell whether a thyroid lump is cancer is by examining the thyroid tissue obtained using a needle or surgery for biopsy.
    Cancer, uterine: Cancer of the womb (uterus). Cancer of the uterus occurs most often in women between the ages of 55 and 70 years. Abnormal bleeding after menopause is the most common symptom of cancer of the uterus. Cancer of the uterus is diagnosed based on the results of the pelvic examination, pap smear, biopsy of the uterus, and D and C procedure.
    Cancer, uterus: Cancer of the womb. Also referred to as uterine cancer. Cancer of the uterus occurs most often in women between the ages of 55 and 70 years. Abnormal bleeding after menopause is the most common symptom of cancer of the uterus. Cancer of the uterus is diagnosed based on the results of the pelvic examination, pap smear, biopsy of the uterus, and D and C procedure.
    Canker sores: Also known as aphthous ulcers, these are small ulcer craters in the lining of the mouth that are frequently painful and sensitive. Canker sores are one of the most common problems that occur in the mouth. About 20% of the population (1 out of 5) people will have canker sores at any one time. Canker sores typically last for 10-14 days and heal without scarring The word canker comes from the Latin cancer for crab. (The Latin cancer was once pronounced kanker from which came canker). Chronic ulcers might seem as hard as a crab shell.
    Capillaries: Capillaries are tiny blood vessels that distribute blood from arteries to the tissues of the body. They are part of the circulatory system. When pink areas of skin are compressed this causes blanching. This occurs because blood is pressed out of the capillaries. (see blood).
    Carbuncles: A skin abscess, a collection of pus that forms inside the body. Antibiotics are often not very helpful in treating abscesses. The main treatments include hot packs and draining ("lancing") the abscess, but only when it is soft and ready to drain. If you have a fever or long-term illness, such as cancer or diabetes, or are taking medications that suppress the immune system, you should contact your healthcare practitioner if you develop an abscess.
    Carcinogen: A substance or agent that is known to cause cancer.
    Carcinoma: Cancer that begins in the tissues lining or covering an organ.
    Carcinoma in situ: Cancer that involves only the cells in which it began and that has not spread to other tissues.
    Cardiac: Having to do with the heart.
    Cardiac muscle: A type of muscle with unique features and only found in the heart.
    Cardiopulmonary: Having to do with both the heart and lungs.
    Cardiopulmonary bypass: Bypass of the heart and lungs as, for example, in open heart surgery. Blood returning to the heart is diverted through a heart-lung machine (a pump-oxygenator) before returning it to the arterial circulation. The machine does the work both of the heart (pump blood) and the lungs (supply oxygen to red blood cells).
    Cardiopulmonary resusitation (CPR): CPR involves breathing for the victim and applying external chest compression to make the heart pump. In the case of an early heart attack, death can often be avoided if a bystander starts CPR promptly (within 5 minutes of the onset of ventricular fibrillation). When paramedics arrive, medications and/or electrical shock (cardioversion) to the heart can be administered to convert ventricular fibrillation to a normal heart rhythm. Therefore, prompt CPR and rapid paramedic respronse can improve the survival chances from a heart attack.
    Carditis: Inflammation of the heart.
    Care proxy, health: A health care proxy is one form of advance medical directive. Advance medical directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There are two basic forms of advance directives:
    (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for health-care decision-making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society).
    Caries: Dental cavities. Holes in the two outer layers of a tooth called the enamel and the dentin. The enamel is the outermost white hard surface and the dentin is the yellow layer just beneath enamel. Both layers serve to protect the inner living tooth tissue called the pulp, where blood vessels and nerves reside. Small cavities may not cause pain, and may be unnoticed by the patient. Larger cavities can collect food, and the inner pulp of the affected tooth can become irritated by bacterial toxins, foods that are cold, hot, sour, or sweet—causing toothache. 
    Carotene, beta: An antioxidant which protects cells against oxidation damage that can lead to cancer. Beta carotene is converted, as needed, to vitamin A. Food sources of beta carotene include vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables; and fruit such as cantaloupes and apricots. Excessive carotene in the diet can temporarily yellow the skin, a condition called carotenemia, commonly seen in infants fed largely mushed carrots.
    Carotenemia: Tempoary yellowing of the skin due to excessive carotene in the diet, commonly seen in infants fed too much mushed carrots or adults consuming high quantities of carrots or beta carotene.
    Carpal tunnel syndrome: Condition caused by irritation of the median nerve at the wrist. Predisposing factors include obesity, pregnancy, hypothyroidism, arthritis, diabetes, and trauma. Tendon inflammation from repetitive work such as prolonged typing is another cause. Symptoms include numbness and tingling of the hand. Diagnosis is suspected based on symptoms, supported by physical examination signs, and confirmed by nerve conduction testing. Treatment of depends on the severity of symptoms and the underlying cause.
    Carrier test: A test designed to detect carriers of a gene for recessive genetic disorder. For example, carrier testing is done for sickle cell trait, thalassemia trait, and the Tay-Sachs gene.
    Cartilage: Firm, rubbery tissue that cushions bones at joints. A more flexible kind of cartilage connects muscles with bones and makes up other parts of the body, such as the larynx and the outside parts of the ears.
    Cataract: A clouding or loss of transparency of the eye lens. There are many causes of cataracts including aging, diabetes, cortisone medication, trauma, or other diseases. Cataracts will affect most people if they live long enough. Symptoms include double or blurred vision and sensitivity to light and glare. Cataracts can be diagnosed when the doctor examines the eyes with a viewing instrument. The ideal treatment for cataracts is surgical implantation of a new lens. Sunglasses can help to prevent cataracts.
    Catheter: A thin, flexible tube. When a catheter is placed in a vein, it provides a pathway for giving drugs, nutrients, fluids, or blood products. Also, blood samples can be withdrawn through the catheter.
    CAT scan: Computerized axial tomography (CAT) scanning adds X-ray images with the aid of a computer to generate cross-sectional views anatomy. It can identify normal and abnormal structures and be used to guide procedures. CAT scanning is painless. Iodine-containing contrast material is sometimes used in CAT scanning. If you having a CAT scan and are allergic to iodine or contrast materials, you should notify your physicians and radiology staff.
    Cauliflower-ear deformity: Destruction of the underlying cartilage framework of the outer ear (pinnae), usually caused by either infection or trauma, resulting in a thickening of the ear. Classically, blood collects (hematoma) between the ear cartilage and the skin. There is a marked thickening of the entire ear which may be so extensive that the shape of the ear becomes unrecognizable. The ear is said to look like a piece of cauliflower. It is typically seen in wrestlers and boxers who have had repeated trauma to the ear.
    Causes of cancer: Cancer is a group of more than 100 different diseases. Benign tumors are not cancer; malignant tumors are cancer. Most cancers are named for the type of cell or the organ in which they begin. When cancer spreads (metastasizes), the new tumor has the same name as the original (primary) tumor. Skin cancer is the most common type of cancer for both men and women. The second most common cancer in men is prostate cancer, in women it is breast cancer. Lung cancer is the leading cause of death from cancer for both men and women in the U.S. Cancer is NOT contagious.
    Cauterization: The use of heat to destroy abnormal cells. Also called diathermy or electrodiathermy.
    Cavities: Holes in the two outer layers of a tooth called the enamel and the dentin. The enamel is the outermost white hard surface and the dentin is the yellow layer just beneath enamel. Both layers serve to protect the inner living tooth tissue called the pulp, where blood vessels and nerves reside. Small cavities may not cause pain, and may be unnoticed by the patient. Larger cavities can collect food, and the inner pulp of the affected tooth can become irritated by bacterial toxins, foods that are cold, hot, sour, or sweet—causing toothache. Also referred to as caries.
    Cavity, abdominal: The space between the abdominal wall and the spine.
    CCD (Central core disease of muscle): One of the conditions that produces ‘floppy baby’ syndrome. CCD causes hypotonia (floppiness) in the newborn baby, slowly progressive muscle weakness, and muscle cramps after exercise. Muscle biopsy shows a key diagnostic finding (absent mitochondria in the center of many type I muscle fibers). CCD is inherited as a dominant trait. The CCD gene is on chromosome 19 (and involves ryanodine receptor-1).
    CD4 count, absolute: The number of "helper" T-lymphocytes in a cubic millimeter of blood. With HIV, the absolute CD4 count declines as the infection progresses. The absolute CD4 count is frequently used to monitor the extent of immune suppression in persons with HIV. Also called a T4 count.
    cDNA: Complementary DNA. cDNA is made from a messenger RNA template. The single- stranded form is often used as a probe in physical mapping.
    CEA assay: A laboratory test to measure the level of carcinoembryonic antigen (CEA), a substance that is sometimes found in an increased amount in the blood of colorectal cancer patients.
    Cecum: The first portion of the large bowel which receives fecal material from the small bowel (ileum). The appendix is also attached to the cecum. The cecum is located in the lower right quadrant of the abdomen.
    Celiac disease, adult: See Celiac sprue.
    Celiac sprue: A result of an immune reaction to gluten, a protein found in wheat or related grains and present in many foods that we eat. Celiac sprue causes impaired absorption and digestion of nutrients through the small intestine. Symptoms include requent diarrhea and weight loss. A skin condition called dermatitis herpetiformis can be associated with celiac sprue. The most accurate test for celiac sprue is a biopsy of the involved small bowel. Treatment is to avoid gluten in the diet. Medications are used for refractory (stubborn) sprue.
    Cell: The basic structural and functional unit in people and all living things. Each cell is a small container of chemicals and water wrapped in a membrane.
    Cell cloning: The process of producing a group of cells (clones), all genetically identical, from a single ancestral cell.
    Cells, reproductive: The eggs and sperm are the reproductive cells. Each mature reproductive cell is haploid in that it has a single set of 23 chromosomes.
    Centimorgan (cM): A unit of measure of genetic recombination frequency. One cM is equal to a 1% chance that a marker at one genetic locus will be separated from a marker at another locus due to crossing over in a single generation. In humans, 1 cM is equivalent, on average, to 1 million base pairs. The centimorgan is named after the pioneering (and Nobel Prize winning) geneticist Thomas Hunt Morgan.
    Central core disease of muscle (CCD): One of the conditions that produces ‘floppy baby’ syndrome. CCD causes hypotonia (floppiness) in the newborn baby, slowly progressive muscle weakness, and muscle cramps after exercise. Muscle biopsy shows a key diagnostic finding (absent mitochondria in the center of many type I muscle fibers). CCD is inherited as a dominant trait. The CCD gene is on chromosome 19 (and involves ryanodine receptor-1).
    Central nervous system: The central nervous system is that part of the nervous system consisting of the brain and spinal cord.
    Centromere: The "waist" of the chromosome essential for the division and the retention of the chromosome in the cell. The centromere is a uniquely specialized region of the chromosome to which spindle fibers attach during cell division.
    CEPH: The Centre d’Etudes du Polymorphisme Humain (CEPH), an internationally reknowned research laboratory created in Paris in 1984 by Professor Jean Dausset (Nobel Prize, Medicine and Physiology, 1980) to provide the scientific community with resources for human genome mapping. Also known as the Fondation Jean Dausset-CEPH.
    Cephalgia: Headache. (One of those things we all know but that defies an easy definition.) Literally, headache is an ache in the head. It is pain in the head. The Greek "algos" means "pain."
    Cerebellum: The portion of the brain in the back of the head between the cerebrum and the brain stem.
    Cerebral hemispheres: The two halves of the cerebrum, the largest part of the brain.
    Cerebritis: Inflammation of the brain.
    Cerebrospinal fluid: The watery fluid that fills the spaces in and around the brain and spinal cord. Also called CSF.
    Cerebrovascular accident (CVA): A stroke. The sudden death of brain cells due to lack of oxygen caused by blockage of blood flow or rupture of an artery to the brain. Sudden weakness or paralysis of one side of the body can be a symptom of a stroke. A suspected stroke can be confirmed by scanning the brain with special X-ray tests, such as CAT scanning. Stroke prevention involves minimizing risk factors, such as controlling high blood pressure and diabetes.
    Cerebrovascular accident (CVA) prevention: In many cases, a person may have a transient ischemic attack (TIA). a neurological event with the symptoms of a stroke, but the symptoms go away within a short period of time. This is often caused by the narrowing or ulceration of the carotid arteries (the major arteries in the neck that supply blood to the brain). If not treated, there is a high risk of having a major stroke in the future. If you suspect a TIA, you should seek medical attention right away. An operation to clean out the carotid artery and restore normal blood flow through the artery (a carotid endarterectomy) markedly reduces the incidence of a subsequent stroke. In other cases, when a person has a narrowed carotid artery, but no symptoms, the risk of having a stroke can be reduced with medications such as aspirin and ticlopidine (TICLID). These medications act by partially blocking the function of blood elements, called platelets, which assist blood clotting.
    Cerebrum: The largest part of the brain. It is divided into two hemipheres, or halves.
    Cervical cancer: Cancer of the entrance to the womb (uterus). Regular pelvic exams and Pap testing can detect precancerous changes in the cervix. Precancerous changes in the cervix may be treated with cryosurgery, cauterization, or laser surgery. The most common symptom of cancer of the cervix is abnormal bleeding. Cancer of the cervix can be diagnosed using a Pap test or other procedures that sample the cervix tissue. Cancer of the cervix requires different treatment than cancer that begin in other parts of the uterus.
    Cervical intraepithelial neoplasia: A general term for the growth of abnormal cells on the surface of the cervix. Numbers from 1 to 3 may be used to describe how much of the cervix contains abnormal cells. Also called CIN.
    Cervical rib: A rib which arises from the seventh cervical vertebrae (above the normal first rib). Occurs in only about 0.5% of people. May cause nerve and artery problems.
    Cervicitis: Inflammation of the cervix.
    Cervix: The cervix, is the end of the womb, or uterus that protrudes into the upper vagina.
    Cesarian section: The obstetrical procedure is often spelled this way in the U.S. with just an "e"although the Roman emperor remains Caesar in America with an "ae". Procedure in which an infant, rather than being born vaginally, is surgically removed from the uterus. Also referred to as a C section. As the name "Caesarian" suggests, this is not exactly a new procedure. It was done in ancient civilizations upon the death of a near-full-term pregnant woman to salvage the baby. Julius Caesar (or one of his predecessors) was born by this procedure. Hence, the name "Caesarian". The term "section" in surgery refers to the division of tissue. What is being divided here is the abdominal wall of the mother as well as the wall of the uterus in order to extract the baby. In Shakespeare’s "Macbeth" the Witches’ prophecy was that "...none of woman born/ Shall harm Macbeth" (IV.i). Unfortunately for Macbeth, the Scottish nobleman Macduff was "from his mother’s womb/ Untimely ripped." and thus not naturally "born of woman"(V.vii). Macduff was the only agent capable of destroying Macbeth. He killed Macbeth in battle. See: Caesarian section.
    Charbon: Known also as anthrax, charbon is a serious bacterial infection. It is not primarily a human disease but rather an infection of animals. Cattle, sheep, horses, mules, and some wild animals are highly susceptible. Humans (and swine) are generally resistant to anthrax. Anthrax can take different forms. With the lung form of the disease. People inhale the anthrax spores and, if untreated, are likely to die. An intestinal form is caused by eating meat contaminated with anthrax. But most human anthrax comes from skin contact with animal products. Cutaneous (skin) anthrax was once well known among people who handled infected animals, like farmers, woolsorters, tanners, brushmakers and carpetmakers in the days when the brushes and carpets were animal products. The hallmark of skin anthrax is a carbuncle, a cluster of boils, that ulcerates in an ugly way. Typically this lesion has a hard black center surrounded by bright red inflammation. This accounts for its name, "anthrax", the Greek word for "coal". "Charbon" in French means "coal."
    Chalazion: Also called a Meibomian cyst or a tarsal cyst, a chalazion is an inflammation of the oil gland of the eyelid.
    Chancre: The classic non-painful ulcer of syphilis. The chancre forms in the first (primary) stage of syphilis, is highly contagious and can last 1-5 weeks. The disease can be transmitted from any contact with one of the ulcers, which are teeming with spirochetes. If the ulcer is outside of the vagina or on the scrotum of the male, the use of condoms may not help in preventing transmission of the disease. Likewise, if the ulcer is in the mouth, merely kissing the infected individual can spread syphilis. (The word chancre is the French for a little ulcer. Chancre and the English canker come from the Latin cancer for crab. Why? Perhaps because chronic ulcers can be hard like the shell of a crab).
    Chemoprevention: The use of natural or laboratory-made substances to prevent cancer.
    Chemotherapy: Treatment with anticancer drugs.
    Chest film: Most common X-ray used to detect abnormalities in or within the thoracic cage, such as the lungs, heart, aorta, and the bones of the chest. Extra metallic objects, such as jewelry are removed from the chest and neck areas for a chest x-ray to avoid interference with x-ray penetration and improve accuracy of the interpretation.
    Chest pain: There are many causes of chest pain. One is angina which results from inadequate oxygen supply to the heart muscle. Angina can be caused by coronary artery disease or spasm of the coronary arteries. Chest pain can also be due to a heart attack (coronary occlusion) and other important diseases. Do not try to ignore chest pain and "work (or play) though it." Chest pain is a warning to seek medical attention.
    Chest X-ray: Commonly used to detect abnormalities in the lungs, but can also detect abnormalities in the heart, aorta, and the bones of the thoracic area. Metallic objects, such as jewelry are removed from the chest and neck areas for a chest x-ray to avoid interference with x-ray penetration and improve accuracy of the interpretation.
    Chickenpox: A highly infectious viral disease, chickenpox is known medically (and in many countries) as varicella. Chickenpox has nothing to do with chicken. The name was meant to distinguish this "weak" form of the pox from smallpox (chicken being used, as in chickenhearted, to mean weak or timid). The "pox" of chickenpox is no major matter unless infected (through scratching) or occur in an immunodeficient person. However, there can be very major problems with chickenpox including pneumonia and encephalitis, particularly in adults but also sometimes in children, and reactivation of the same herpes virus is reponsible for shingles (zoster). The current aim in the U.S. is to achieve universal (or nearly universal) immunization of children with the chickenpox vaccine.
    Chickenpox immunization: This vaccine prevents the common disease known as chickenpox (varicella zoster). While chickenpox is often considered a trivial illness, it can cause significant lost time on the job and in school and have serious complications including ear infections, pneumonia, and infection of the rash with bacteria, inflammation of the brain (encephalitis) leading to difficulty with balance and coordination (cerebellar ataxia), damaged nerves (palsies), and Reye’s syndrome, a potentially fatal complication. The vaccination requires only one shot given at about a year of age. If an older person has not had chickenpox, the shot may be given at any time. There have been few significant reactions to the chickenpox vaccine. All children, except those with a compromised immune system, should have the vaccination.
    Chilblains: A form of cold injuries along with"trench foot," and frostbite. Cold injuries occur with and without freezing of body tissues. The young and the elderly are especially prone to cold injury. Alcohol increases the risk of cold injury which can lead to loss of body parts and even to death. It is important not to thaw an extremity if there is a risk of it re-freezing.
    Children’s immunizations: In the United States, it is recommended that all children receive vaccination against:
    Hepatitis B 
    Diphtheria, tetanus, pertussis 
    Haemophilus influenzae type B (HIB) 
    Poliovirus 
    Measles, mumps, rubella 
    Varicella zoster virus (chickenpox). 
    Every child in the U.S. should have these vaccinations except when there are special circumstances and the child’s doctor advises specifically against a vaccination. 
    Chiropractic: A system of diagnosis and healing based on the concept that health and disease are related to nervous system function, disease is due to malfunction of the nervous system due to noxious irritants, and health can be restored by their removal.
    Chiropractor: Someone who practices chiropractic.
    Chlamydia: A bacteria that causes infection very similar to gonorrhea in the way that it is spread and the symptoms it produces. Like gonorrhea, it is found in the cervix and urethra and can live in the throat or rectum. It is very destructive to the tubes (fallopian tubes) that transport eggs from a woman’s ovary to the womb and can cause infertility and tubal pregnancy and severe pelvic infection. Because it is common for infected women to have no symptoms, it is often untreated, leading to extensive destruction of the fallopian tubes and fertility problems. Like gonorrhea, chlamydia is associated with an increased incidence of preterm births. The infant can also acquire the disease during passage through the birth canal, leading to eye involvement or pneumonia. For this reason, all newborns are treated with eye drops after birth. The drops contain an antibiotic which treats chlamydia. Treatment of all newborns is routine because of the large number of infected women without symptoms, and the dire consequences of chlamydial eye infection to the newborn.
    Cholecystitis: Inflammation of the gallbladder, a complication of gallstones which are formed by cholesterol and pigment (bilirubin) in bile. (Bile is produced in the liver and stored in the gallbladder). Cholecystitis is frequently associated with infection in the gallbladder. Risk factors for cholesterol gallstones include age, obesity, female gender, multiple pregnancies, birth control pills, and heredity. The most common symptom is pain in the upper abdomen. Diagnosis is usually made with ultrasound of the abdomen. Some patients have no symptoms. Patients with mild and infrequent symptoms may consider oral medication to dissolve gallstones. Surgery (standard or laparoscopic) is considered for patients with severe symptoms and for patient with cholecystitis.
    Cholesterol: The most common steroid in the body, cholesterol is produced in the liver and carried in the bloodstream by lipoproteins. LDL (Low-Density Lipoprotein) cholesterol (the "bad" cholesterol) is associated with an increased risk of coronary artery (heart) disease. After age 20 years, cholesterol level testing is recommended every 5 years. Diets high in cholesterol and saturated fats can increase blood cholesterol levels. Diets high in unsaturated fats can lower blood cholesterol. The most effective means of lowering blood cholesterol is to reduce dietary saturated fat intake. Treatment of elevated cholesterol includes diet, weight loss, regular exercise, and occasionally medications.
    Chondroplasia: The formation of cartilage by specialized cells called chondrocytes.
    Chondrosarcoma: A cancer that forms in cartilage.
    Chordae tendineae: Thread-like bands of fibrous tissue which attach on one end to the edges of the tricuspid and mitral valves and on the other to the papillary muscles.
    Chordoma: A form of bone cancer that usually starts in the lower spinal column.
    Chorion: The outermost of the two fetal membranes—the amnion is the innermost --. which together surround the embryo. The chorion develops villi (vascular fingers) and gives rise to the placenta. In Greek, the word "chorion" means "skin or leather."
    Chorionic villus sampling (CVS): Procedure used at 8-10 weeks of pregnancy for prenatal diagnosis (diagnosis of conditions of the fetus before birth). Tissue is withdrawn from an area of the placenta, namely the villi of the chorion.
    Chromatids: The daughter strands of a duplicated chromosome joined together by a centromere.
    Chromosomes: Chromosomes are microscopic components of every cell in the body that carry all of the genetic material that will eventually determine hair color, eye color and our overall appearance and makeup.
    Chromosome complement: The whole set of chromosomes for the species. In humans, the chromosome complement (which is also called the karyotype) consists of 46 chromosomes.
    Chromosome disorder: An abnormal condition due to an abnormality of the chromosomes. For example, Down syndrome (the genetic abnormality featuring three chromosome 21s, instead of two, also refered to as trisomy 21) is a chromosome disorder.
    Chromosome map: The chart of the linear array of genes on a chromosome. The Human Genome Project aims to map all of the human chromosomes.
    Chromosomes in multiple miscarriages: Couples who have had more than one miscarriage (spontaneous abortion) have about a 5% chance that one member of the couple is carrying a chromsome translocation responsible for the miscarriages.
    Chronic: This is an important term in medicine. It comes from the Greek chronos meaning time (as in chronometer). It means lasting a long time. A chronic condition is one lasting 3 months or more, by the definition of the U.S. National Center for Health Statistics. In ancient Greece, the "father of medicine" Hippocrates distinguished diseases that were acute (abrupt, sharp and brief) from those that were chronic. This is still a very useful distinction. Subacute has been coined to designate the mid-ground between acute and chronic.
    Chronic arthritis, systemic-onset juvenile (Still’s disease): Also known as systemic-onset juvenile rheumatoid arthritis, this is a form of joint disease (arthritis) that presents with systemic (bodywide) symptoms including a high intermittent fever, a transient salmon-colored skin rash, swollen lymph glands, enlargement of the liver and spleen, and inflammation of the lungs (pleuritis) and around the heart (pericarditis) The arthritis may not be apparent at first but it always surfaces and may persists long after the systemic symptoms are gone.
    Chronic fatigue syndrome (CFS): A debilitating medical condition, chronic in nature, cause unknown, diagnosis by exclusion, no known verified test, treatment by relief of symptoms, life style changes, and occasionally time. Known also as Chronic Fatigue and Immune Dysfunction Syndrome (CFIDS) and as Myalgic Encephalomyelitis (ME), there has been some debate over the existence and causes of this condition.
    Chronic leukemia: Cancer of the blood cells (leukemia) that progresses slowly.
    Chronic phase: Refers to the early stages of chronic myelogenous leukemia. The number of immature, abnormal white blood cells in the bone marrow and blood is higher than normal, but lower than in the accelerated or blast phase.
    Chronicity: Characterized by long duration. The state of being chronic.
    Circulation: The movement of fluid in a regular or circuitous course. Although the noun "circulation" does not necessarily refer to the circulation of the blood, for all practical purposes today it does. Heart failure is an example of a problem with the circulation.
    Circulation, fetal: The blood circulation in the fetus (the unborn baby). Before birth, the blood from the heart that is destined (in the pulmonary artery) for the lungs is shunted away from the lungs and returned to the greatest of arteries (the aorta). The shunt is through a short vessel called the ductus arteriosus. When this shunt is open, it is said to be a patent (pronounced pá tent) ductus arteriosus (PDA). The PDA usually closes at or shortly after birth and blood is permitted to course freely to the lungs.
    Circulatory: Having to do with the circulation, the movement of fluid in a regular or circuitous course. Although the adjective "circulatory" need not necessarily refer to the circulation of the blood, for all practical purposes today it does. A circulatory problem is taken usually to be a problem with the blood circulation, for example with heart failure.
    Circulatory System: The circulatory system is a composed of the heart, arteries, capillaries and veins. It serves to transport blood low in oxygen from the body to the lungs and heart (veins) and oxygenated blood from the lungs and heart throughout the body (arteries). (see heart, blood).
    Cirrhosis: An abnormal liver condition characterized by irreversible scarring of the liver. Alcohol and viral hepatitis B and C are among the many causes of cirrhosis. Cirrhosis can cause yellowing of the skin (jaundice), itching, and fatigue. Diagnosis of cirrhosis can be suggested by physical examination and blood tests, and can be confirmed by liver biopsy in some patients. Complications of cirrhosis include mental confusion, coma, fluid accumulation (ascites), internal bleeding, and kidney failure. Treatment of cirrhosis is designed to limit any further damage to the liver as well as complications. Liver transplantation is becoming an important option for patients with advanced cirrhosis.
    Cl: The chemical symbol for chloride. Sodium chloride (ordinary salt) is chemically represented NaCl.
    Clap: Gonorrhea, a bacterial infection transmitted by sexual contact. Gonorrhea is one of the oldest known sexually transmitted diseases (STDs). In women infected with this bacteria (Neisseria gonorrhoeae), 25-40% will also be infected with another bacteria that can cause another STD called chlamydia. Gonorrhea is NOT transmitted from toilet seats. More than half of women infected with gonorrhea do not have any symptoms. If symptoms occur, they may include burning or frequent urination, yellowish vaginal discharge, redness and swelling of the genitals, and a burning or itching of the vaginal area. Untreated, gonorrhea can lead to severe pelvic infections.
    Clavicle: The bone extending from the breastbone (sternum) at the base of the front of the neck to the shoulder.
    Cleft uvula: The uvula, the little V-shaped fleshy mass hanging from the back of the soft palate, is cleft. . Cleft uvula is a common minor anomaly occurring in about 1% of whites and 10% of Native Americans. Persons with a cleft uvula should not have their adenoids removed because, without the adenoids, they cannot achieve proper closure between the soft palate and pharynx while speaking and develop hypernasal speech. Also called bifid uvula.
    Click-murmur syndrome: Mitral valve prolapse (also known as "Barlow’s syndrome"), the most common heart valve abnormality, affecting 5-10% of the world population. Most patients have no symptoms and require no treatment, but some have fatigue and/or palpitations. The mitral valve prolapse can often be detected by a doctor during examination of the heart and confirmed with an echocardiogram. Patients are usually given antibiotics prior to any procedure which might introduce bacteria into the bloodstream, including dental work and minor surgery, because of an increased risk of infection of the abnormal heart valve.
    Clinical cytogenetics: The application of chromosome studies to clinical medicine. For example, clinical cytogenetic testing is done to see if a child with possible Down syndrome has an extra chromosome #21, as is most often the case. Clinical Cytogenetics is a specialty certified by the American Board Of Medical Genetics.
    Clinical research trials: Evaluating the safety and effectiveness of medications or medical devices by monitoring their effects on large groups of people. Clinical medical trials sponsored by the U. S. government are listed on a web site of the National Institutes of Health (NIH). The NIH Clinical Center intends to make details of current clinical research studies for various diseases available over the Internet to increase opportunities for patients and physicians to participate in clinical investigations. The site is at http://www.cc.nih.gov/nihstudies/
    Clinical trials: Medical research studies conducted with volunteers. Each study is designed to answer scientific questions and to find better ways to prevent, detect, or treat cancer.
    Clitoris: A small mass of erectile tissue situated at the anterior apex of the vestibule.
    Clone: Literally a fragment, the word in modern medical science has come to mean a replica, for example, of a group of bacteria or a macromolecule such as DNA. Clone also refers to an individual developed from a single somatic (non-germ) cell from a parent, representing an exact replica of that parent. A clone is a group of cells derived from a single ancestral cell.
    Clone bank: Synonym for Genomic library.
    Cloning: The process by which a genetically identical copy is made.
    Cloning, cell: The process of producing a group of cells (clones), all genetically identical, from a single ancestor.
    Cloning, DNA: The use of DNA manipulation procedures to produce multiple copies of a single gene or segment of DNA.
    Clones, recombinant: Clones containing recombinant DNA molecules.
    Clostridium difficile (C.difficile): A bacterium, one of the most common causes of infection of the large bowel (colon) in the U.S. affecting millions of people yearly. Patients taking antibiotics are at risk of becoming infected with C. difficile.Antibiotics disrupt the normal bacteria of the bowel, allowing C. difficile bacteria to become established in the colon. Many persons infected with C. difficile bacteria have no symptoms. These people become carriers of the bacteria and can infect others. In other people, a toxin produced by C. difficile causes diarrhea, abdominal pain, severe inflammation of the colon (colitis), fever, an elevated white blood count, vomiting and dehydration. In severely affected patients, the inner lining of the colon becomes severely inflamed (a condition called pseudomembranous colitis). Rarely, the walls of the colon wear away and holes develop (colon perforation), which can lead to a life-threatening infection of the abdomen.
    Clot-dissolving medications: Agents such as plasminogen-activator (t-PA) and streptokinase that are effective in dissolving clots and re-opening arteries. Used, for example, in the treatment of heart attacks. Also called thrombolytic agents.
    Clubfoot: A common malformation of the foot evident at birth. The medical term for the common ("classic") type of clubfoot is talipes equinovarus. The Latin word talipes was compounded from talus (ankle) + pes (foot) since, with a clubfoot, the foot is turned in sharply and the person seems to be walking on their ankle. Equino- indicates the heel is elevated (like a horse’s) and -varus indicates it is turned inward.
    cM: A centimorgan, a unit of measure of genetic recombination frequency. One cM is equal to a 1% chance that a marker at one genetic locus will be separated from a marker at another locus due to crossing over in a single generation. In humans, 1 cM is equivalent, on average, to 1 million base pairs. The centimorgan is named after the pioneering (and Nobel Prize winning) geneticist Thomas Hunt Morgan.
    CNS: Central nervous system.
    CNS prophylaxis: Chemotherapy or radiation therapy to the central nervous system (CNS). This is preventative treatment. It is given to kill cancer cells that may be in the brain and spinal cord, even though no cancer has been detected there.
    Cocci: pleural of coccus. Bacteria which are spherically shaped.
    Coccus: a bacterial cell which has the shape of a sphere.
    Coccyx: The small tail-like bone at the bottom of the spine very near to the anus.
    Code: The genetic code is the correspondence between the triplet of bases in DNA with the amino acids. The discovery of the genetic code clearly ranks as one of the premiere events of what has been called the Golden Age of Biology (and Medicine).
    Codon: A triplet of any three of chemical components in the genetic material called bases.
    Coefficient of inbreeding: A statistical way of gauging how close two people are as to the genes. The coefficient of inbreeding (symbolized as F) is the probability that a person with two identical genes received both genes from an identical ancestor. Take first cousins who by definition share a set of grandparents. So for any particular allele (gene) in the father, the chance that the mother inherited the same allele from the same source is 1/8. Further, for any gene the father passes to his child, the chance is 1/8 that the mother has the same gene and ½ that she transmits that gene to the child so 1/8 X ½ = 1/16. Thus, a first-cousin marriage has a coefficient of inbreeding F =1/16. The added risks to the offspring of first cousins depend not only upon this coefficient of inbreeding but also upon the genetic family history and, in some cases, upon test results (for example, for beta thalassemia for first cousins of Italian descent). However, there are always added risks from the mating of closely related persons and those risks are not negligible.
    Colchicine: A substance found in a plant that is used in clinical medicine for the treatment of gouty arthritis and in the laboratory to arrest cells during cell division (by disrupting the spindle) so their chromosomes can be visualized. The name colchicine is from the Greek kolchikon meaning autumn crocus or meadow saffron, the plant from which colchicine was originally isolated.
    Colpo-: Combining form from the Greek kolpos meaning a fold, cleft, or hollow and usually referring to the vagina. Words incorporating colpo- as the start of the word include colporrhaphy, colposcopy, colpotomy.
    Cold, common: A viral upper respiratory tract infection. A contagious illness caused by a number of different types of viruses. Because of the great number of viruses that can cause a cold, the body never builds up resistance (immune) against all of them. For this reason, colds are a frequent and recurring problem. In fact, preschool children average 9 colds a year; those in kindergarten, 12 colds a year; and adolescents and adults, 7 colds per year. Going out into the cold weather has no effect on the spread of a cold. Antibiotics do not help the common cold.
    Cold injury: Cold injuries include chilblains, "trench foot," and frostbite. Cold injuries occur with and without freezing of body tissues. The young and the elderly are especially prone to cold injury. Alcohol increases the risk of cold injury which can lead to loss of body parts and even to death.. It is important not to thaw an extremity if there is a risk of it re-freezing.
    Colectomy: An operation to remove all or part of the colon. In a partial colectomy, the surgeon removes only the cancerous part of the colon and a small amount (called a margin) of surrounding healthy tissue.
    Colic: An attack of abdominal pain and crying in infant. Overfeeding, undiluted juices, food allergies, and emotional stress can aggravate colic. It is important for a baby with new abdominal pain and crying to be evaluated by a doctor who can exclude other more serious conditions.
    Colitis: Inflammation of the large intestine (the colon). There are many forms of colitis, including ulcerative, Crohn’s, infectious, pseudomembranous, and spastic. For example, intermittent rectal bleeding, crampy abdominal pain and diarrhea can be symptoms of ulcerative colitis. Diagnosis can be made by barium enema, but direct visualization (sigmoidoscopy or colonoscopy) is the most accurate test. Long-standing ulcerative colitis increases the risk for colon cancer. Ulcerative colitis can also be associated with inflammation in joints, spine, skin, eyes, the liver and its bile ducts. Treatment of ulcerative colitis can involve medications and surgery.
    Colitis, Crohn’s: Crohn’s disease affecting only the large intestine (colon). The disease usually affects persons in their teens or early twenties. It tends to be chronic, recurrent with periods of remission and exacerbation. In the early stages, it causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs. Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery. (The disease is also called granulomatous enteritis or regional enteritis).
    Colitis, mucus: A common gastrointestinal disorder characterized by abdominal pain, bloating, mucous in stools, and irregular bowel habits with alternating diarrhea and constipation, symptoms that tend to be chronic and wax and wane over the years. Although mucus colitis can cause chronic recurrent discomfort, it appears to be an abnormal condition of gut contractions (motility) and does not lead to any serious organ problems. Diagnosis usually involves excluding other illnesses. Treatment is directed toward relief of symptoms and includes high fiber diet, exercise, relaxation techniques, avoidance of caffeine, milk products and sweeteners, and medications. Alternative names include irritable bowel syndrome, spastic colitis and nervous colon syndrome.
    Colitis, pseudomembranous: Severe inflammation of the inner lining of the colon due usually to the clostridium difficile (C.difficile) bacterium, one of the most common causes of infection of the large bowel (colon) in the United States, affecting millions of patients yearly. Patients taking antibiotics are at risk of becoming infected with C. difficile. Antibiotics disrupt the natural bacteria of the bowel, allowing C. difficile bacteria to become established in the colon. Many persons infected with C. difficile bacteria have no symptoms. These people become carriers of the bacteria and can infect others. In some people, a toxin produced by C. difficile causes diarrhea, abdominal pain, severe inflammation of the colon (colitis), fever, an elevated white blood count, vomiting and dehydration. Rarely, the walls of the colon wear away and holes develop (colon perforation), which can lead to a life-threatening infection of the abdomen.
    Colitis, spastic: See Colitis, mucus.
    Colitis, ulcerative: Inflammation of the large intestine (the colon). Cause unknown. Intermittent rectal bleeding, crampy abdominal pain and diarrhea can be symptoms of ulcerative colitis. Diagnosis can be made by barium enema, but direct visualization (sigmoidoscopy or colonoscopy) is the most accurate test. Long-standing ulcerative colitis increases the risk for colon cancer. Ulcerative colitis can also be associated with inflammation in joints, spine, skin, eyes, the liver and its bile ducts. Treatment of ulcerative colitis can involve medications and surgery.
    Collagen: Collagen is the principal protein of the skin, tendons, cartilage, bone and connective tissue.
    Colon: The long, coiled, tubelike organ that removes water from digested food. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus. The colon is sometimes called the large bowel or the large intestine.
    Colon cancer: A malignant tumor arising from the inner wall of the large intestine. The third leading cause of cancer in males, fourth in females in the U.S. Risk factors for colorectal cancer include heredity, colon polyps, and long standing ulcerative colitis. Most colorectal cancers develop from polyps. Removal of colon polyps can prevent colorectal cancer. Colon polyps and early cancer can have no symptoms. Therefore regular screening is important. Diagnosis can be made by barium enema or by colonoscopy with biopsy confirmation of cancer tissue. Surgery is the most common treatment for colorectal cancer.
    Colon cancer and polyps: Benign tumors of the large intestine are called polyps. Malignant tumors of the large intestine are called cancers. Benign polyps do not invade nearby tissue or spread to other parts of the body. Benign polyps can be easily removed during colonoscopy, and are not life threatening. If benign polyps are not removed from the large intestine, they can become malignant (cancerous) over time. Most of the cancers of the large intestine are believed to have developed from polyps.
    Colon cancer, family history of: Colorectal cancer can run in families. The colon cancer risk is higher if an immediate (first-degree) family member (parents, siblings or children) had colorectal cancer and even higher if more than one such relative had colorectal cancer or if a family member developed the cancer at young age (younger than 55 years). Under any of these circumstances, individuals are recommended to undergo a colonoscopy every three years starting at an age that is 7-10 years younger than when the youngest family member with the cancer wasdiagnosed. For example, if a parent had colon cancer diagnosed at age 50, colonoscopy should start in that person’s children at 40-43 years of age.
    Colonoscope: A flexible, lighted instrument used to view the inside of the colon.
    Colonoscopy: Colonoscopy is a procedure whereby a doctor inserts a viewing tube (colonoscope) into the rectum for the purpose of inspecting the colon. Upon detecting certain abnormal areas of the colon a biopsy can be performed.
    Colony-stimulating factors: Laboratory-made agents similar to substances in the body that stimulate the production of blood cells. Treatment with colony-stimuating factors (CSFs) can help the blood-forming tissue recover from the effects of chemotherapy and radiation therapy.
    Colorectal: Related to the colon and/or rectum.
    Colorectal cancer: Cancer of the colon and rectum. A malignant tumor arising from the inner wall of the large intestine. Risk factors include heredity, colon polyps, and long standing ulcerative colitis. Most colorectal cancers develop from polyps. Removal of colon polyps can prevent colorectal cancer. Since colon polyps and early cancer can have no symptoms, regular screening is important. Diagnosis can be made by barium enema or by colonoscopy with biopsy confirmation of cancer tissue. Surgery is the most common treatment for colorectal cancer.
    Colostomy: An altered exit from the colon by diverting from a hole in the colon through the wall of the abdomen. A colostomy is commonly performed by severing the colon to attach the end leading to the stomach to the skin through the wall of the abdomen. The end of the colon that leads to the rectum is closed off and becomes dormant. This is known as a "Hartmann’s Colostomy". There are other types of colostomy procedures, but this one is the most common. Usually a colostomy is performed for infection, blockage, or in rare instances, severe trauma of the colon. This is not an operation to be taken lightly. It demands the close attention of both patient and doctor. A colostomy is often performed so that an infection can be stopped and/or the affected colon tissues can heal.
    Colostomy, a patient’s perspective: For an excellent article about colostomy from a patient’s viewpoint, we recommend "Colostomy...a Patient’s Perspective" by Craig J. McCracken. This article is available here at MedicineNet.
    Colporrhaphy: Surgical repair of the vagina. The -rrhaphy part of the word comes from the Greek raphe meaning suture.
    Colposcopy: A procedure in which a lighted magnifying instrument (called a colposcope) is used to examine the vagina and cervix.
    Colpotomy: A surgical incision in the vagina. The -tomy part of the word comes from the Greek tome meaning cutting.
    Coma: A state of unarousable unconsciousness.
    Common bile duct: The duct formed by the junction of the cystic duct from the gallbladder and the common hepatic duct from the liver. Carries bile to the duodenum.
    Common cold: A viral upper respiratory tract infection. A contagious illness caused by a number of different types of viruses. Because of the great number of viruses that can cause a cold, the body never builds up resistance (immune) against all of them. For this reason, colds are a frequent and recurring problem. In fact, preschool children average 9 colds a year; those in kindergarten, 12 colds a year; and adolescents and adults, 7 colds per year. Going out into the cold weather has no effect on the spread of a cold. Antibiotics do not help the common cold.
    Complementary DNA (cDNA): DNA made from a messenger RNA template. The single-stranded form is often used as a probe in physical mapping.
    Complementary sequence: Nucleic acid sequence of bases that can form a double- stranded structure by matching base pairs. For example, the complementary sequence to C-A-T-G (where each letter stands for one of the bases in DNA) is G-T-A-C.
    Complete hysterectomy: Complete surgical removal of the uterus and cervix.
    Also called a total hysterectomy.
    Compound microscope: A microscope (an optical instrument that augments the power of the eye to see small objects) which consists of two microscopes in series, the first serving as the ocular lens (close to the eye) and the second serving as the objective lens (close to the object to be viewed). Credit for creating the compound microscope goes usually to the Dutch spectaclemakers Hans and Zacharias Janssen who in 1590 invented an instrument that could be used as either a microscope or telescope. The compound microscope has evolved into the dominant type of optical microscope today.
    Computed tomography: An x-ray procedure that uses a computer to produce a detailed picture of a cross section of the body; also called CAT or CT scan.
    Computerized axial tomography (CAT): Cat scanning adds X-ray images with the aid of a computer to generate cross-sectional views anatomy. It can identify normal and abnormal structures and be used to guide procedures. CAT scanning is painless. Iodine-containing contrast material is sometimes used in CAT scanning. If you are having a CAT scan and are allergic to iodine or contrast materials, you should notify your physicians and radiology staff.
    Concussion: A concussion is a traumatic injury of soft tissue, usually the brain, as a result of a violent blow or shaking. A brain concussion can cause immediate and temporary impairment of brain function, such as thinking, vision, equilibrium and consciousness.
    Condyloma acuminatum: Warts confined primarily to the moist skin of the genitals and around the anus due to viruses belonging to the family of human papilloma viruses (HPVs) transmitted through sexual contact. Most infected people have no symptoms but these viruses increase a woman’s risk for cancer of the cervix. The virus can also be transmitted from mother to baby during childbirth. HPV infection is the most common sexually transmitted disease in the United States. It is also the leading cause of abnormal PAP smears and pre-cancerous changes of the cervix in women. There is no cure for genital warts virus infection. Once contracted, the virus can stay with a person for life.
    Condylomata acuminata: Genital warts caused by certain human papillomaviruses. Congenital: Present at birth.
    Congenital defect: A birth defect.
    Congenital heart disease: A birth defect of the heart or great blood vessels (like the aorta).
    Congenital malformation: Abnormal formation of a structure evident at birth.
    Conization: Surgery to remove a cone-shaped piece of tissue from the cervix and cervical canal. Conization may be used to diagnose or treat a cervical condition. Also called cone biopsy.
    Conjunctivitis: Inflammation of the membrane covering the surface of the eyeball. It can be a result of infection, irritation, or related to systemic diseases, such as Reiter’s syndrome.
    Conjunctivitis, alllergic: Inflammation of the whites of the eyes (the conjunctivae) with itching and redness of the eyes and tearing, due to allergy. Frequently accompanies hayfever.
    Connective tissue: Connective tissue is a material consisting of fibers that form a framework that provides support structure for body tissues.
    Conor and Bruch’s disease: African tick typhus, one of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (tache noire) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash. Also called boutonneuse and fièvre boutonneuse.
    Conn’s syndrome: Overproduction of the hormone aldosterone by a tumor containing tissue like that in the outer portion (cortex) of the adrenal gland. The excess aldosterone (pronounced al’-do-ster-one) results in low potassium levels (hypokalemia), underacidity of the body (alkalosis), muscle weakness, excess thirst (polydipsia), excess urination (polyuria), and high blood pressure (hypertension). Also called primary aldosteronism and hyperaldosteronism. Named after the American physician Jerome W. Conn.
    Consanguinity: Everyone carries rare recessive alleles, rare genes that are generally innocuous in the heterozygous state but that in the company of another gene of the same type are capable of causing an autosomal recessive disease. We are all reservoirs for genetic disease. First cousins, as noted, share a set of grandparents. So for any particular allele (gene) in the father, the chance that the mother inherited the same allele from the same source is 1/8. Further, for any gene the father passes to his child, the chance is 1/8 that the mother has the same gene and ½ that she transmits that gene to the child so 1/8 X ½ = 1/16. Thus, a first-cousin marriage has a coefficient of inbreeding of 1/16. The added risks for first cousins depend not only upon this coefficient of inbreeding but also upon their genetic family histories and, in some cases, upon test results (for example, for beta thalassemia for first cousins of Italian descent). However, there are always added risks from the mating of closely related persos and those risks are not negligible.
    Conserved sequence: A base sequence in a DNA molecule (or an amino acid sequence in a protein) that has remained essentially unchanged, and so has been conserved, throughout evolution.
    Constipation: Infrequent (and frequently incomplete) bowel movements. The opposite of diarrhea, constipation is commonly caused by irritable bowel syndrome, diverticulosis, and medications (constipation can paradoxically be caused by overuse of laxatives). Colon cancer can narrow the colon and thereby cause constipation. The large bowel (colon) can be visualized by barium enema x-rays, sigmoidoscopy, and colonoscopy. Barring a condition such as cancer, high-fiber diets can frequently relieve the constipation.
    Contig: Group of clones representing overlapping regions of the genome.
    Contig map: A map depicting the relative order of a linked library of small overlapping clones representing a complete chromosome segment.
    Contraceptive device, intrauterine (IUD): A device inserted into the uterus (womb) to prevent conception (pregnancy). The IUD can be a coil, loop, triangle, or T in shape made of plastic or metal.
    Contraceptive device, intrauterine (IUD): A device inserted into the uterus (womb) to prevent conception (pregnancy). The IUD can be a coil, loop, triangle, or T in shape made of plastic or metal.
    Contralateral: On the other side. The opposite of iposilateral (the same side). For example, a stroke involving the right side of the brain may cause contralateral paralysis of the leg (that is, of the left leg).
    Contusion: Another name for a bruise. What is a bruise ? A bruise, or contusion, is caused when blood vessels are damaged or broken as the result of a blow to the skin (be it bumping against something or hitting yourself with a hammer). The raised area of a bump or bruise results from blood leaking from these injured blood vessels into the tissues as well as from the body’s response to the injury. A purplish, flat bruise that occurs when blood leaks out into the top layers of skin is referred to as an ecchymosis.
    Coronal: A coronal plane through the body is a vertical plane from head to foot and parallel to the shoulders.
    Coronary artery bypass graft (CABG): Coronary artery disease develops because of hardening of the arteries (atherosclerosis) that supply blood to the heart muscle. Diagnostic tests include EKG, stress test, echocardiography, and coronary angiography. CABG surgery is advised for selected groups of patients with significant narrowings and blockages of the heart arteries (coronary artery disease) to create new routes around narrowed and blocked arteries, permitting increased blood flow to deliver oxygen and nutrients to the heart muscles. The bypass graft for a CABG can be a vein from the leg or an inner chest wall artery. CABG surgery is performed about 350,000 times annually in the United States, making it one of the most commonly performed major operations.
    Corpora cavernosa: Two chambers in the penis which run the length of the organ and are filled with spongy tissue. Blood flows in and fills the open spaces in the spongy tissue to create an erection.
    Corpus: The body of the uterus (womb).
    Coryza: A runny nose. The word "coryza" came from the Greek "koryza" thought to have been compounded from "kara", head + "zeein", to boil = boiling over from the head.
    Cosmid: An artificially constructed vector (carrier) used in cloning pieces of DNA. (On a technical level, a cosmid contains the cos gene of phage lambda and can be packaged in a lambda phage particle for infection into E. coli, permitting cloning of larger DNA fragments that can be introduced into bacterial hosts in plasmid vectors). Cultural evolution: By contrast with biologic evolution, A.G. Motulsky in 1968 noted that social evolution is mediated by ideas, shows a rapid (exponential) rate of change, is usually purposeful, often beneficial, is widely disseminated by diverse means, is frequently transmitted in complex ways, further complexity comes from the frequent formation of new ideas and new technologies. Cultural evolution is unique to humans among all forms of life. Human culture required biologic evolution to achieve the human brain. See Biologic evolution.
    Costal margin: The lower edge of the chest (thorax) formed by the bottom edge of the rib cage.
    Cortex: The outer layer of an organ. The cerebral cortex is the outer portion of the cerebrum, the main part of the brain.
    Cortical: Having to do with the cortex, the outer layer of an organ.
    Corticosteroid: Any of the steroid hormones made by the cortex (outer layer) of the adrenal gland. Cortisol is a corticosteroid.
    Cortisol: The primary stress hormone. Cortisol is the major natural GLUCOCORTICOID (GC) in humans.
    Costochondritis: Costochondritis is the result of inflammation of the cartilage of the chest wall, usually involving that which surrounds the breast bone (sternum). It causes local pain and tenderness of the chest around the sternum.
    Cousin marriage: See: Consanguinity.
    CPR: Cardiopulmonary resusitation. CPR involves breathing for the victim and applying external chest compression to make the heart pump. In the case of an early heart attack, death can often be avoided if a bystander starts CPR promptly (within 5 minutes of the onset of ventricular fibrillation). When paramedics arrive, medications and/or electrical shock (cardioversion) to the heart can be administered to convert ventricular fibrillation to a normal heart rhythm. Therefore, prompt CPR and rapid paramedic respronse can improve the survival chances from a heart attack.
    Cracked tooth syndrome: A toothache caused by a broken tooth (tooth fracture) without associated cavity or advanced gum disease. Biting on the area of tooth fracture can cause severe sharp pains. These fractures are usually due to chewing or biting hard objects such as hard candies, pencils, nuts, etc. Sometimes, the fracture can be seen by painting a special dye on the cracked tooth. Treatment usually is to protect the tooth with a crown. However, if placing a crown does not relieve pain symptoms, a root canal procedure may be necessary.
    Cramp,writer’s: A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs during handwriting. Similar focal dystonias have also been called typist’s cramp, pianist’s cramp, musician’s cramp, and golfer’s cramp.
    Cranial arteritis: A serious disease characterized by inflammation of the walls of the blood vessels (vasculitis). The vessels affected by inflammation are the arteries (hence the name "arteritis"). The age of affected patients is usually over 50 years of age. Cranial arteritis is also known as temporal arteritis and as giant cell arteritis. It can lead to blindness and/or stroke. The disease is detected by a biopsy of an artery. It is treated with high dose cortisone-related medications.
    Cranial dystonia: A term used to describe dystonia that affects the muscles of the head, face, and neck. Oromandibular dystonia affects the muscles of the jaw, lips, and tongue. The jaw may be pulled either open or shut, and speech and swallowing can be difficult. Spasmodic dysphonia involves the muscles of the throat that control speech. Also called spastic dysphonia or laryngeal dystonia, it causes strained and difficult speaking or breathy and effortful speech. Meige’s syndrome is the combination of blepharospasm and oromandibular dystonia and sometimes spasmodic dysphonia. Spasmodic torticollis can be classified as a type of cranial dystonia.
    Craniopharyngioma: A type of brain tumor.
    Craniotomy: An operation in which an opening is made in the skull so the doctor can reach the brain.
    Cranium: The top portion of the skull which protects the brain. The bones of the cranium include the frontal, parietal, occipital, temporal, sphenoid, and ethmoid.
    Creutzfeldt-Jakob disease (CJD): A dementing disease of the brain. It is believed due to an unconventional (not a bacteria or virus), transmissible agent called a prion. Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome, Jakob-Creutzfeldt disease, and spastic pseuodoparalysis.
    Crib death: The sudden and unexpected death of a baby with no known illness, typically affecting infants from 2 weeks to 6 months of age while sleeping. Crib death is now called Sudden Infant Death Syndrome (SIDS). Babies at an increased risk for SIDS include those with a brother or sister who died of SIDS; children whose mothers smoked or used heroin, methadone, or cocaine during pregnancy; infants born weighing less than 4.4 pounds (2000 grams); children with an abnormal breathing pattern with long periods without taking a breath (apnea); and babies who sleep on their stomachs. Since babies who sleep on their stomachs are at least 3 times more likely to die of SIDS than babies who sleep on their backs, children’s health authorities such as the American Academy of Pediatrics recommend always placing infants on their backs to sleep.
    Crohn’s colitis: Crohn’s disease involving only the large intestine (colon).
    Crohn’s disease: A chronic inflammatory disease of the intestine primarily in the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition with periods of remission and exacerbation. In the early stages, Crohn’s disease causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs.When only the large intestine (colon) is involved, the condition is called Crohn’s colitis. When only the small intestine is involved, the condition is called Crohn’s enteritis. When only the end of the small intestine (the terminal ileum) is involved, it is termed terminal ileitis. When both the small intestine and the large intestine are involved, the condition is called Crohn’s enterocolitis (or ileocolitis). Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery. (The disease is also called granulomatous enteritis or regional enteritis).
    Crohn’s enteris: Crohn’s disease (regional enteritis) involving only the small intestine.
    Crohn’s enterocolitis: Crohn’s disease involving both the small and large intestines.
    Crohn’s ileocolitis: Crohn’s disease involving the ileum (the lowest portion of the small intestine) and the colon (the large intestine).
    Crossing over: The exchange of genetic material between two paired chromosomes. Crossing over is a way to recombine the genetic material so that each person (except for identical twins) is genetically unique.
    Croup: An infection of the larynx, trachea, and the bronchial tubes, mainly in children. Caused usually by viruses, less often by bacteria. Symptoms include a cough that sounds like a barking seal and a harsh crowing sound during inhaling. Treatment can include moist air, salt water nose drops, decongestants and cough suppressants, pain medication, fluids, and occasionally antibiotics. The major concern in croup is breathing difficulty as the air passages narrow. Close monitoring of the breathing of a child with croup is important, especially at night. While most children recover from croup without hospitalization, some children can develop life-threatening breathing difficulties. Therefore, close contact with the doctor during this illness is important.
    Cryosurgery: Treatment performed with an instrument that freezes and destroys abnormal tissue.
    Cryptorchidism: A condition in which one or both testicles fail to move from the abdomen, where they develop before birth, into the scrotum; also called undescended testicles. Boys who have had cryptorchidism that was not corrected in early childhood are at increased risk for developing cancer of the testicles.
    CT (or CAT) scan: A series of detailed pictures of areas inside the body created by a computer linked to an x-ray machine. Also called computed tomography (CT) scan or computed axial tomography (CAT) scan.
    Culture: A culture is the propagation of microorganisms in a growth media. Any body tissue or fluid can be evaluated in the laboratory by culture techniques in order to detect and identify infectious processes. Culture techniques also be used to determine sensitivity to antibiotics.
    Curettage: Removal of tissue with a curette.
    Curette: A spoon-shaped instrument with a sharp edge.
    Cushing’s syndrome: The constellation of symptoms and signs caused by an excess of cortisol hormone. Cushing syndrome is an extremely complex hormonal condition that involves many areas of the body. Common symptoms are thinning of the skin, weakness, weight gain, bruising, hypertension, diabetes, thin weak bones (osteoporosis), facial puffiness, and in women cessation of periods. Ironically, one of the commonest causes of Cushing’s syndrome is the administration of "cortisol-like medications" for the treatment of diverse diseases. All other cases of Cushing’s syndrome are due to excess production of cortisol by the adrenal gland including 1) an abnormal growth of the pituitary gland, which stimulates the adrenal gland, 2) a benign or malignant growth within the adrenal gland itself, which produces cortisol and 3) production within another part of the body (ectopic production) of a hormone that directly or indirectly stimulates the adrenal gland to make cortisol. Neurosurgeon Harvey Cushing (1869-1939) described hyperadrenocorticism (excessive production of cortisol by the adrenal gland) due quite specifically to an ACTH-secreting pituitary adenoma, a benign pituitary tumor that puts out ACTH (AdrenoCorticoTropic Hormone) which, in turn, drives (or overdrives) the adrenal gland to overproduce cortisol.
    Cusp: In reference to heart valves, one of the triangular segments of the valve which opens and closes with the flow of blood. In reference to teeth, a raised area of the biting surface.
    Cutaneous: Related to the skin.
    Cuts: Severed skin. Washing a cut or scrape with soap and water and keeping it clean and dry is all that is required to care for most wounds. Putting alcohol hydrogen peroxide, and iodine into a wound can delay healing and should be avoided. Seek medical care early if you think that you might need stitches. Any delay can increase the rate of wound infection. Any puncture wound through tennis shoes has a high risk of infection and should be seen by your healthcare professional. Any redness, swelling, increased pain, or pus draining from the wound may indicate an infection that requires professional care.
    CVS: See Chorionic villus sampling.
    Cyst: A closed sac or capsule, usually filled with fluid or semisolid material.
    Cyst, Baker’s: A swelling in the space behind the knee (the popliteal space) composed of a membrane-lined sac filled with synovial fluid that has escaped from the joint. Named after the British surgeon William Morrant Baker (1839-1896). Also called a synovial cyst of the popliteal space.
    Cyst, Meibomian: Also called a chalazian or a tarsal cyst, an inflammation of the oil gland of the eyelid.
    Cyst, pilonidal: A special kind of abscess that occurs in the cleft between the buttocks. Forms frequently in adolescence after long trips that involve sitting.
    Cyst, sebaceous: A sebaceous cyst is a rounded swollen area of the skin formed by an abnormal sac of retained excretion (sebum) from the sebaceous follicles.
    Cyst, synovial, of the popliteal space: A swelling in the space behind the knee (the popliteal space). The swelling is composed of a membrane-lined sac filled with synovial fluid that has escaped from the joint. Commonly called Baker’s cyst.
    Cyst, tarsal: Also called a chalazian or a Meibomian cyst, an inflammation of the oil gland of the eyelid.
    Cyst thyroglossal: A thyroglossal cyst is a fluid-filled sac present at birth and located in the midline of the neck. A thyroglossal cyst is a result of incomplete closure of a segent of a tube-like structure (the thyroglossal duct) that is present, and normally closes, as the embryo develops. A thyroglossal cyst is also called a thyrolingual cyst.
    Cyst, thyrolingual: A thyrolingual cyst is a fluid-filled sac that is present at birth and located in the midline of the neck. A thyrolingual cyst is a result of incomplete closure of a segent of a tube-like structure (the thyrolingual duct) that is present, and normally closes, as the embryo develops. A thyrolingual cyst is also called a thyroglossal cyst.
    Cystectomy: Surgery to remove the bladder. Cystic fibrosis: A common genetic disease inherited as a recessive condition. Thick mucus can clog the lung passages and block the ducts of the pancreas in cystic fibrosis.
    Cystic acne: This is a type of localized infection (abscess) formed when oil ducts become clogged and infected. Cystic acne is most common in the teenage years.
    Cystic fibrosis (CF): One of the most common serious genetic (inherited) diseases. The CF gene is carried by 1/20 persons (in Caucasian populations) and 1 in 400 couples is at risk for having children with CF. CF is characterized by the production of abnormal secretions leading to mucous build-up. which can impair the pancreas (and, secondarily, the intestine). CF mucous build-up in lungs can impair respiration. Without treatment, CF results in death for 95% of children before age 5. Early diagnosis of CF is of great importance. Early and continuing treatment of CF is valuable.
    Cystitis: Inflammation of the bladder. Cystitis can be due for example to infection from bacteria that ascend the urethra (the canal from the outside) to the bladder.
    Cystitis, interstitial (IC): Disease that involves inflammation or irritation of the bladder wall. This inflammation can lead to scarring and stiffening of the bladder, and even ulcerations and bleeding. Diagnosis is based on symptoms, findings on cystoscopy and biopsy, and eliminating other treatable causes such as infection. Because doctors do not know what causes IC, treatments are aimed at relieving symptoms. Most people are helped for variable periods of time by one or a combination of treatments.
    Cystoscope: An instrument that allows the doctor to see inside the bladder and remove tissue samples or small tumors.
    Cystoscopy: A procedure in which the doctor inserts a lighted instrument into the urethra (the tube leading from the bladder to the outside of the body) to look at the bladder.
    Cytogenetics: The study of the chromosomes, the visible carriers of the hereditary material. Cytogenetics is a fusion science due to joining of cytology (the study of cells) with genetics (the study of inherited variation).
    Cytogenetics, clinical: The application of cytogenetics to clinical medicine. For example, clinical cytogenetic studies might be done to determine whether a child with possible Down syndrome has an extra chromosome #21.
    Cytometry, flow: Analysis of biological material by detection of the light-absorbing or fluorescing properties of cells or subcellular fractions such as chromosomes passing in a narrow stream through a laser beam. Flow cytometry is used with automated sorting devices to sort successive droplets of the stream into different fractions depending on the fluorescence emitted by each droplet.
    Cytoplasm: The substance of the cell outside the nucleus.
    Cytosine (C): One member of the G-C (guanine-cytosine) pair of bases in DNA.

  • D & C: Dilatation and curettage, a minor operation in which the cervix is expanded enough (dilatation) to permit the cervical canal and uterine lining to be scraped with a spoon-shaped instrument called a curette (curettage).
    Dactylitis: Inflammation of a digit (either a finger or a toe).
    Death rate: The number of deaths in the population divided by the average population (or the population at midyear) is the crude death rate. In 1994, for example, the crude death rate per 1,000 population was 8.8 in the United States, 7.1 in Australia, etc. A death rate can also be tabulated according to age or cause.
    Decongestants: Drugs that shrink the swollen membranes in the nose and make it easier to breath. Decongestants can be taken orally or by nasal spray. Decongestant nasal spray should not be used for more than five days without the doctor"s advice, and if so, usually only when accompanied by a nasal steroid. Many decongestant nasal sprays often cause a rebound effect if taken too long. A rebound effect is the worsening of symptoms when a drug is discontinued. This is a result of a tissue dependence on the medication. Decongestants should not be used by patients with high blood pressure (hypertension) unless under doctor’s supervision.
    Defect, atrial septal (ASD): A hole in the septum, the wall, between the atria, the upper chambers of the heart. Commonly called an ASD. ASDs are a major class of congenital cardiac malformation.
    Defect, enzyme: An abnormality in the protein (enzyme) important in catalyzing a normal biochemical reaction in the body. Disorders result from a deficiency (or functional abnormality) of an enzyme. Archibald Garrod in 1902 was the first to attribute a disease to an enzyme defect: an inborn error of metabolism. Today, newborns are routinely screened for certain enzyme defects such as phenylketonuria (PKU) and galactosemia, an error in the handling (metabolism) of the sugar galactose.
    Defect, ventricular septal (VSD): A hole in the interventricular septum, the wall between the ventricles (lower chambers of the heart). Commonly called a VSD. VSDs are a common class of heart deformity present at birth (congenital cardiac malformation).
    Deficiency, alpha-1 antitrypsin: An inherited disease with little or no production of an important protein, alpha-1 antitrypsin. The lack of this protein leads to damage of various organs, mainly the lung and liver. The disease may become apparent at a very early age or in adulthood, as shortness of breath or liver-related symptoms (jaundice, fatigue, fluid in the abdomen, mental changes, or gastrointestinal bleeding). There are several options for treatment of the lung disease, including replacement of the missing protein. Treatment of the liver disease is a well-timed liver transplant
    Deficiency, calcium: A low blood calcium (hypocalcemia). Hypocalcemia makes the nervous system highly irritable with tetany (spasms of the hands and feet, muscle cramps, abdominal cramps, overly active reflexes, etc.). Chronic calcium deficiency contributes to poor mineralization of bones, soft bones (osteomalacia) and osteoporosis; and, in children, rickets and impaired growth. Food sources of calcium include dairy foods, some leafy green vegetables such as broccoli and collards, canned salmon, clams, oysters, calcium-fortified foods, and tofu. According to the National Academy of Sciences, adequate intake of calcium is 1 gram daily for both men and women. The upper limit for calcium intake is 2.5 grams daily.
    Deficiency dermatitis and diarrhea, zinc: A genetic disease called acrodermatitis enteropathica is characterized by the simultaneous occurrence of skin inflammation (dermatitis) and diarrhea. The skin on the cheeks, elbows and knees and tissue about the mouth and anus are inflammed. There is also balding of the scalp, eyebrows and lashes, delayed wound healing and recurrent bacterial and fungal infections due to immune deficiency. The key laboratory finding is an abnormally low blood zinc level reflecting impaired zinc uptake. Oral treatment with zinc is curative.
    Deficiency, glucocerebrosidase: Causes Gaucher’s disease (type 1), a progressive genetic disease, due to an enzyme defect. The enzyme, glucocerebrosidase, is needed to break down the chemical glucocerebroside. The enzyme defect in persons with Gaucher’s disease (GD) leads to the accumulation of glucocerebroside in the spleen, liver, and lymph nodes. The most common early sign is enlargement of the spleen (located in the upper left abdomen). Other signs include low red blood cell counts (anemia), a decrease in blood clotting cells (platelets), increased pigmentation of the skin, and a yellow fatty spot on the white of the eye (a pinguecula). Severe bone involvement can lead to pain and collapse of the bone of the hips, shoulders, and spine. The GD gene is on chromosome 1. The disease is a recessive trait. Both parents carry a GD gene and transmit it for their child with the disease. The parents’ risk of a child with the disease is 1 in 4 with each pregnancy. This type of Gaucher’s disease (noncerebral juvenile Gaucher’s disease) is most common in Ashkenazi Jews (of European origin) and is the most common genetic disease among Jews in the United States.
    Deficiency, glucose-6-phosphate dehydrogenase (G6PD): Deficiency of G6PD is the commonest disease-causing enzyme defect in humans affecting an estimated 400 million people. The G6PD gene is on the X chromosome. Males with the enzyme deficiency develop anemia due to breakup of their red blood cells when they are exposed to oxidant drugs such as the antimalarial primaquine, the sulfonamide antibiotics or sulfones, naphthalene moth balls, or fava beans.
    Deficiency, iron: Deficiency of iron results in anemia because iron is necessary to make hemoglobin, the key molecule in red blood cells responsible for the transport of oxygen. In iron deficiency anemia, the red cells are unusally small (microcytic) and pale (hypochromic). Characteristic features of iron deficiency anemia in children include failure to thrive (grow) and increased infections. The treatment of iron deficiency anemia , whether it be in children or adults, is with iron and iron-containing foods. Food sources of iron include meat, poultry, eggs, vegetables and cereals (especially those fortified with iron). According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men.
    Deficiency, lactase: Lack of the enzyme lactase resulting in failure to digest lactose in milk (lactose intolerance).
    Deficiency, magnesium: Can occur due to inadequate intake or impaired intestinal absorption of magnesium. Low magnesium (hypomagnesemia) is often associated with low calcium (hypocalcemia) and potassium (hypokalemia) levels. Deficiency of magnesium causes increased irritability of the nervous system with tetany (spasms of the hands and feet, muscular twitching and cramps, spasm of the larynx, etc.). According to the National Academy of Sciences, the Recommended Dietary Allowances of magnesium are 420milligrams per day for men and 320 milligrams per day for women. The upperlimit of magnesium as supplements is 350 milligrams daily, in addition to the magnesium from food and water.
    Deficiency, protein C: Protein C is a protein in plasma that enters into the cascade of biochemical events leading to the formation of a clot. Deficiency of protein C results in thrombotic (clotting) disease.
    Deficiency, selenium: Deficiency of the essential mineral selenium causes Keshan disease, a fatal form of cardiomyopathy (disease of the heart muscle) first observed in Keshan province in China and since found elsewhere. According to the National Academy of Sciences, the Recommended Dietary Allowances of selenium are 70 milligrams per day for men and 55 milligrams per day for women. Food sources of selenium include seafoods, some meats such as kidney and liver, and some grains and seeds.
    Deficiency, zinc: Deficiency of zinc is associated with short stature, anemia, increased pigmentation of skin (hyperpigmentation), enlarged liver and spleen (hepatosplenomegaly), impaired gonadal function (hypogonadism), impaired wound healing, and immune deficiency. (For a genetic disorder that impairs zinc uptake, please see Acrodermatitis enteropathica). According to the National Academy of Sciences, the Recommended Dietary Allowances of zinc are 12 milligrams per day for women and 10 milligrams per day for men. Food sources of zinc include meat including liver, eggs, seafood, nuts and cereal.
    Deformation: A change from the normal size or shape. Also called deformity. A deformation can be present at birth (congenital) or develop after birth (acquired).
    Degenerative arthritis: Also known as osteoarthritis, this type of arthritis is caused by inflammation, breakdown and eventual loss of the cartilage of the joints. Among the over 100 different types of arthritis conditions, osteoarthritis is the most common, affecting usually the hands, feet, spine, and large weight-bearing joints, such as the hips and knees. Also called degenerative joint disease.
    Degenerative joint disease: Also known as osteoarthritis, this type of arthritis is caused by inflammation, breakdown and eventual loss of the cartilage of the joints. Among the over 100 different types of arthritis conditions, osteoarthritis is the most common, affecting usually the hands, feet, spine, and large weight-bearing joints, such as the hips and knees. Also called degenerative arthritis.
    Dehydration: Excessive loss of body water. Diseases of the gastrointestinal tract may lead to dehydration. One clue to dehydration is a rapid drop in weight. A loss of over 10% (15 pounds in a person weighing 150 pounds) is considered severe. Symptoms include increasing thirst, dry mouth, weakness or lightheadedness (particularly if worsening on standing), or a darkening/decrease in urination are suggestive. Severe dehydration can lead to changes in the body’s chemistry, kidney failure, and become life-threatening. The best way to treat dehydration is to prevent it from occurring. If one suspects fluid loss is excessive, notify a physician. Intravenous or oral fluid replacement may be needed.
    Dehydration: Excessive loss of body water.
    Delay, developmental: Behind schedule in reaching milestones of early childhood development.
    Deletion: Loss of a segment of DNA from a chromosome. An example is the cat-cry (cri du chat) syndrome which is due to loss of part of chromosome 5. A deletion is the opposite of a duplication.
    Dementia: Significant loss of intellectual abilities such as memory capacity, severe enough to interfere with social or occupational functioning.
    Dental braces (orthodontics): The use of devices to move teeth or adjust underlying bone. The ideal age for starting orthodontic treatment is between ages 3 to 12 years. Temporomandibular joint (TMJ) problems can be corrected with splinting or dental braces. Teeth can be moved by removable appliances or by fixed braces. Crowding of teeth can require extraction of teeth. Retainers may be necessary long after dental braces are placed, especially with orthodontic treatment of adults.
    Dental impaction: Teeth pressing together. For example, molar teeth (the large teeth in the back of the jaw) can be impacted, cause pain and require pain medication, antibiotics, and surgical removal.
    Dental pain (toothache): The most common cause of a toothache is a dental cavity. The second most common is gum disease. Toothache can be caused by a problem that does not originate from a tooth or the jaw.
    Dentin: Dentin is the hard tissue of the tooth surrounding the central core of nerves and blood vessels (pulp).
    Deoxyribonucleic acid (DNA): The molecule that encodes the genetic information. DNA is a double-stranded molecule that is held together by weak bonds between base pairs of nucleotides to form a double helix. The four nucleotides in DNA contain the bases: adenine (A), guanine (G), cytosine ©, and thymine(T). Base pairs form naturally only between A and T and between G and C so the base sequence of each single strand of DNA can be simply deduced from that of its partner strand. The code is in triplets such as ATG. The base sequence of that triplet in the partner strand is therefore TAC.
    Department of Energy (DOE). One of the U.S. government agencies contributing to the Human Genome Project.
    Depression: Low spirits; dejection. Symptoms of depression include apathy, anorexia, lack of emotional expression (flat affect), social withdrawal and fatigue. Prevalent types of depression are major depression, dysthymia, and bipolar disorder. Some types of depression run in families. The first step to getting appropriate treatment is a complete physical and psychological evaluation to determine whether one, in fact, has a depressive illness.
    Depression, bipolar: Formerly called manic- depressive illness. Not nearly as prevalent as other forms of depressive disorders, bipolar disorder involves cycles of depression and elation or mania. Sometimes the mood switches are dramatic and rapid, but most often they are gradual. When in the depressed cycle, you can have any or all of the symptoms of a depressive disorder. When in the manic cycle, any or all symptoms listed under mania may be experienced. Mania often affects thinking, judgment, and social behavior in ways that cause serious problems and embarrassment. For example, unwise business or financial decisions may be made when an individual is in a manic phase. Bipolar disorder is often a chronic recurring condition.
    Depression, dysthmia: A less severe type of depression, dysthymia involves long-term chronic symptoms that do not disable, but keep one from functioning at "full steam" or from feeling good. Sometimes people with dysthymia also experience major depressive episodes.
    Depression, major: Major depression is manifested by a combination of symptoms (see Depression, symptoms of) that interfere with the ability to work, sleep, eat, and enjoy once pleasurable activities. These disabling episodes of depression can occur once, twice, or several times in a lifetime.
    Dermatitis: Inflammation of the skin.
    Dermatologic: Having to do with the skin.
    Dermatologist: A doctor who specializes in the diagnosis and treatment of skin problems.
    Dermatome: (1) A localized area of skin that is has its sensation via a single nerve from a single nerve root of the spinal cord. Shingles (herpes zoster) typically affects one or several isolated dermatomes. (2) A dermatome is also a cutting instrument used for skin grafting or slicing thin pieces of skin.
    Dermatomyositis: Dermatomyositis is a chronic inflammatory disease of muscle which is associated with patches of slightly raised reddish or scaly rash. The rash can be on the bridge of the nose, around the eyes, or on sun-exposed areas of the neck and chest. Classically, however, it is over the knuckles. (see polymyositis).
    Dermatopathy: Any disease of the skin. Synonymous with dermopathy.
    Dermatophytic onychomycosis: Ringworm of the nail, the most common fungus infection of the nails (onychomycosis). Onychomycosis makes the nails look white and opaque, thickened, and brittle. Older women (perhaps because estrogen deficiency may increase the risk of infection). and men and women with diabetes or disease of the small blood vessels (peripheral vacscular disease) are at increased risk. Artificial nails (acrylic or "wraps") increase the risk because when an artificial nail is applied, the nail surface is usually abraded with an emery board damaging it, emery boards can carry infection, and. water can collect under the nail creating a moist, warm environment for fungal growth.Alternative names include tinea unguium.
    Dermis: The lower or inner layer of the two main layers of cells that make up the skin.
    Dermopathy: Any disease of the skin. Synonymous with dermatopathy.
    Desensitization, allergy: Stimulation of the immune system with gradually increasing doses of the substances to which a person is allergic, the aim being to modify or stop the allergy "war" (by reducing the strength of the IgE and its effect on the mast cells). This form of treatment is very effective for allergies to pollen, mites, cats, and especially stinging insects (eg, bees, hornets, yellowjackets, wasps, velvet ants, fire ants). Allergy immunotherapy usually takes 6 months to a year to become effective and shots (injections) are usually required for 3-5 years.
    Designer estrogen: An engineered drug that possesses some, but not all, of the actions of estrogen. Designer estrogens are selective estrogen-receptor modulators (SERMs). For example, raloxifene (trade name Evista) is classified as a SERM because it prevents bone loss (like estrogen) and lowers serum cholesterol (like estrogen) but (unlike estrogen) does not stimulate the endometrial lining of the uterus.
    Development: The process of growth and differentiation.
    Developmental delay: Behind schedule in reaching milestones of early childhood development.
    Device, assistive: Any device that is designed, made, and/or adapted to assist a person to perform a particular task. For examples, canes, crutches, walkers, wheel chairs, and shower chairs are all assistive devices. Device, intrauterine contraceptive (IUD): A device inserted into the uterus (womb) to prevent conception (pregnancy). The IUD can be a coil, loop, triangle, or T in shape made of plastic or metal.
    Dextro-: From the Latin dexter meaning on the right side. For example, a molecule that shows dextrorotation is turning or twisting to the right. The opposition of dextro- is levo- (from the Latin laevus meaning on the left side) so the opposite of dextrorotation is levorotation.
    Dextrocardia: The heart is reversed and is in the right side of the chest rather than in its normal location on the left. This is a true anatomic reversal. With dextrocardia, for example, the apex (tip) of the heart points to the right rather than (as is normal) to the left. Dextrocardia occurs in an abnormal condition present at birth (congenital) called Kartagener’s syndrome.
    Dextroposition: Move to the right.
    Dextroposition of the heart: The heart is displaced to the right (from its usual location in the left chest). There is no anatomic alteration in the heart itself, just in its location. Dextroposition occurs when the contents of the left side of the chest shove the heart to the right or when the contents of the right chest are reduced (for example, by collapse of the right lung) and the heart moves toward the sparsely occupied space on the right.
    Diabetes and fiber: Soluble fibers (oat bran, apples, citrus, pears, peas/beans, psyllium, etc.) slow down the digestion of carbohydrates (sugars), which results in better glucose metabolism. Some patients with the adult-onset diabetes may actually be successfully treated with a high-fiber diet alone, and those on insulin, can often reduce their insulin requirements by adhering to a high-fiber diet.
    Diabetes mellitus: A chronic condition associated with abnormally high levels of sugar (glucose) in the blood.. Absence or insufficient production of insulin (which is produced by the pancreas and lowers blood glucose) causes diabetes. The two types of diabetes are referred to as insulin dependent (type I) and non-insulin dependent (type II). Symptoms of diabetes include increased urine output and appetite as well as fatigue. Diabetes mellitus is diagnosed by blood sugar (glucose) testing. The major complications of diabetes mellitus include dangerously elevated blood sugar, abnormally low blood sugar due to diabetes medications, and disease of the blood vessels which can damage the eye, kidneys, nerves, and heart. Treatment depends on the type of the diabetes.
    Diabetes, type 1: Insulin dependent diabetes or juvenile diabetes.
    Diabetes, type 2: Non-insulin dependent diabetes, adult-onset diabetes or insulin-resistant diabetes.
    Diagnosis: The nature of a disease.
    Dialysis: The process of cleansing the blood by passing it through a special machine. Dialysis is necessary when the kidneys are not able to filter the blood. Dialysis allows patients with kidney failure a chance to live productive lives. There are two types of dialysis: hemodialysis and peritoneal dialysis. Each type of dialysis has advantages and disadvantages. Patients can often choose the type of long term dialysis that best matches their needs.
    Dialysis, peritoneal: Technique that uses the patient’s own body tissues inside of the belly (abdominal cavity) to act as a filter. The intestines lie in the abdominal cavity, the space between the abdominal wall and the spine. A plastic tube called a "dialysis catheter" is placed through the abdominal wall into the abdominal cavity. A special fluid is then flushed into the abdominal cavity and washes around the intestines. The intestinal walls act as a filter between this fluid and the blood stream. By using different types of solutions, waste products and excess water can be removed from the body through this process.
    Diaper rash: Also called "diaper dermatitis," a diaper rash is a skin inflammatory reaction localized to the area usually covered by the diaper. It can have many causes including infections (yeast, bacterial or viral), friction irritation, chemical allergies (perfumes, soaps), sweat and plugging of sweat glands.

    Diaphragm: The muscle that separates the chest (thoracic) cavity from the abdomen. Contraction of the diaphragm muscle helps to expand the lungs when breathing air inward.
    Diaphragmatic hernia: Passage of a loop of bowel through the diaphragm muscle. This type of hernia occurs as the bowel from the abdomen "herniates" upward through the diaphragm into the chest (thoracic) cavity.
    Diarrhea: Unusually liquid bowel movements.
    Diarrhea, antibiotic-induced: A bacterium called Clostridium difficile (C.difficile), one of the most common causes of infection of the large bowel (colon). Patients taking antibiotics are at particular risk of becoming infected with C. difficile. Antibiotics disrupt the normal bacteria of the bowel, allowing C. difficile bacteria (and other bacteria) to become established and overgrow the colon. Many persons infected with C. difficile bacteria have no symptoms but can become carriers of the bacteria and infect others. In other people, a toxin produced by C. difficile causes diarrhea, abdominal pain, severe inflammation of the colon (colitis), fever, an elevated white blood count, vomiting and dehydration. In severely affected patients, the inner lining of the colon becomes severely inflamed (a condition called pseudomembranous colitis). Rarely, the walls of the colon wear away and holes develop (colon perforation), which can lead to a life-threatening infection of the abdomen.
    Diathermy: The use of heat to destroy abnormal cells. Also called cauterization or electrodiathermy.
    Dicentric: An abnormal chromosome with two centromeres as opposed to the normal one entromere.
    Diethylstilbestrol: A drug that was once widely prescribed to prevent miscarriage. Women whose mothers were given diethylstilbestrol (DES) during pregnancy to prevent miscarriage are at increased risk for developing cancer of the cervix.
    Differential diagnosis: The process of weighing the probability of one disease versus that of other diseases possibly accounting for a patient's symptoms.
    Differentiation: The process of change during development that leads to the progressive diversity in structure and function of cells.
    Diffuse idiopathic skeletal hyperostosis (DISH) : A form of degenerative arthritis characteristically associated with flowing calcification along the sides of the vertebrae of the spine and commonly with inflammation (tendinitis) and calcification of the tendons at their attachments points to bone. Because areas of the spine and tendons can become inflamed, antiinflammatory medications (NSAIDs), such ibuprofen, can be helpful in both relieving pain and inflammation. Also called Forestier’s disease.
    Digestive system: The organs that are responsible for getting food into and out of the body and for making use of food to keep the body healthy. These include the mouth, esophagus, stomach, liver, gallbladder, pancreas, small intestine, colon, and rectum.
    Digital rectal exam: An exam to detect rectal cancer. The doctor inserts a lubricated, gloved finger into the rectum and feels for abnormal areas. It is also an important screening test for the detection of prostate abnormalities, including cancer.
    DiGeorge syndrome (DGS): This disorder is characterized by (1) low blood calcium levels (hypocalcemia) due to underdevelopment (hypoplasia) of the parathyroid glands needed to control calcium; (2) underdevelopment (hypoplasia) of the thymus, an organ behind the breastbone in which lymphocytes mature and multiply; and (3) defects involving the outflow tracts from the heart. Most cases of DGS are due to a very small deletion (microdeletion) in chromosome band 22q11.2. A small number of cases have defects in other chromosomes, notably 10p13. Named after the American pediatric endocrinologist Angelo DiGeorge. Other names for DGS include hypoplasia of the thymus and parathyroids and the third and fourth pharyngeal pouch syndrome.
    Digit, supernumerary: An extra finger or toe.
    Dilatation and curettage: A minor operation in which the cervix is expanded enough (dilatation) to permit the cervical canal and uterine lining to be scraped with a spoon-shaped instrument called a curette (curettage) This procedure also is called D and C.
    Dilate: To stretch or enlarge.
    Dilator: A device used to stretch or enlarge an opening. Patients with scarring of the muscular tube through which food passes from the throat to the stomach (esophagus) can require a dilator procedure in order to open the esophagus for adequate passage of food and fluids.
    Diphtheria: An acute infectious disease that typically strikes the upper respiratory tract including the throat. Diphtheria can be deadly. It is one of the diseases that the DTP (Diphtheria-Tetanus-Pertussis) and DTaP (Diphtheria-Tetanus-acellular Pertussis) vaccines are designed to prevent.
    Diploid: The number of chromosomes in most cells of the body. This number is 46 in humans. It is naturally twice the haploid number of 23 chromosomes contained in human eggs (ova) and sperm.
    Diplopia: The condition whereby a single object appears as two objects. Also called "double vision."
    Directives, advance medical: Advance directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There ared two basic types of advance directives: (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for health-care decision-making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society).
    Disaster Supplies Kit: You and your family can cope best by preparing for disaster before it strikes. One way to prepare is by assembling a Disaster Supplies Kit. Once disaster hits, you won’t have time to shop or search for supplies. But if you’ve gathered supplies in advance, your family can endure an evacuation or home confinement. For useful information, see the MedicineNet site on YOUR FAMILY DISASTER SUPPLIES KIT.
    Disease: Illness or sickness often characterized by typical patient problems (symptoms) and physical findings (signs). Disruption sequence: The events that occur when a fetus that is developing normally is subjected to a destructive agent such as the rubella (German measles) virus.
    Disease, Addison’s: Long-term underfunction of the outer portion of the adrenal gland. In medical terms, chronic insufficiency of the adrenal cortex. This may be due to a number of different insults to the adrenal including physical trauma, hemorrhage, and tuberculosis of the adrenal, and destruction of the cells in the pituitary gland that secrete ACTH (adrenocorticotropic hormone) which normally drives the adrenal. Addison’s disease is characterized by bronzing of the skin, anemia, weakness, and low blood pressure. The U.S. President J.F. Kennedy is said to have had Addison’s disease. Named after the British physician Thomas Addison (1793-1860).
    Disease, adult celiac: This condition results from an immune (allergic) reaction to gluten, a protein found in wheat and related grains and present in many foods that we eat. Sprue causes impaired absorption and digestion of nutrients through the small intestine. Symptoms include requent diarrhea and weight loss. A skin condition called dermatitis herpetiformis can be associated with celiac sprue. The most accurate diagnostic test for sprue is a biopsy of the involved small bowel. Treatment is to avoid gluten in the diet. Medications are used for refractory (stubborn) sprue. Known under a number of other names, including celiac sprue.
    Disease, Alzheimer’s: A progressive degenerative disease of the brain that leads to dementia. On a cellular level, Alzheimer’s is characterized by unusual helical protein filaments in nerve cells (neurons) of the brain. These odd twisted filaments are called neurofibrillary tangles. On a functional level, there is degeneration of the cortical regions, especially the frontal and temporal lobes, of the brain. The U.S. President Ronald Reagan is said to have Alzheimer’s disease. Named after the German neurologist Alois Alzheimer (1864-1915).
    Disease, bipolar: A type of depressive disease, formerly called manic-depressive illness. Not nearly as prevalent as other forms of depressive disorders. Bipolar disorder involves alternating cycles of depression and elation or mania. Sometimes the mood switches are dramatic and rapid, but most often they are gradual. Mania often affects thinking, judgment, and social behavior in ways that cause serious problems and embarrassment. For example, unwise business or financial decisions may be made when an individual is in a manic phase. Bipolar disorder is often a chronic recurring condition.
    Disease, Brill-Zinsser: Recrudescence of epidemic typhus years after the initial attack. The agent that causes epidemic typhus (Rickettsia prowazekii) remains viable for many years and then when host defenses are down, it is reactivated causing recurrent typhus. The disease is named for the physician Nathan Brill and the great bacteriologist Hans Zinsser.
    Disease, central core, of muscle (CCD): One of the conditions that produces ‘floppy baby’ syndrome. CCD causes hypotonia (floppiness) in the newborn baby, slowly progressive muscle weakness, and muscle cramps after exercise. Muscle biopsy shows a key diagnostic finding (absent mitochondria in the center of many type I muscle fibers). CCD is inherited as a dominant trait. The CCD gene is on chromosome 19 (and involves ryanodine receptor-1).
    Disease, congenital heart: A birth defect of the heart or great blood vessels (like the aorta).
    Disease, Conor and Bruch’s: African tick typhus, one of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (tache noire) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash. Also called boutonneuse and fièvre boutonneuse.
    Disease, Creutzfeldt-Jakob (CJD): A dementing disease of the brain. It is believed due to an unconventional (not a bacteria or virus), transmissible agent called a prion. Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome, Jakob-Creutzfeldt disease, and spastic pseuodoparalysis.
    Disease, Crohn’s: A chronic inflammatory disease of the intestine. Named after Burrill Crohn who described the disease in 1932. It usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition withperiods of remission and exacerbation. In the early stages, there are small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel. The bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis)and in adjacent organs. When only the large intestine (colon) is involved, the condition is called Crohn’s colitis. When only the small intestine is involved, the condition is called Crohn’s enteritis. When only the end of the small intestine (the terminal ileum) is involved, it is termed terminal ileitis.When both the small intestine and the large intestine are involved, the condition is called Crohn’s enterocolitis (or ileocolitis). Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, orsurgery. (The disease is also called granulomatous enteritis or regionalenteritis).
    Disease, degenerative joint: Also known as osteoarthritis, this type of arthritis is caused by inflammation, breakdown and eventual loss of the cartilage of the joints. Among the over 100 different types of arthritis conditions, osteoarthritis is the most common, affecting usually the hands, feet, spine, and large weight-bearing joints, such as the hips and knees. Also called degenerative arthritis.
    Disease, fifth (erythema infectiosum): In the pre-vaccination era, it was frequently the "fifth disease" that a child would develop. It is caused by a virus known as parvovirus B 19. Symptoms include low-grade fever, fatigue, a "slapped cheeks rash," and a rash over the whole body. While the illness is not serious in children, 80% of adults have joint aches and pains (arthritis) which may become long-term with stiffness in the morning, redness and swelling of the same joints on both sides of the body (a "symmetrical" arthritis), most commonly involving the knees, fingers, and wrists. Pregnant women (who have not previously had the illness) should avoid contact with patients who have fifth disease. The fifth disease virus can infect the fetus prior to birth. And, while no birth defects have been reported as a result of fifth disease, it can cause the death of the unborn fetus. The risk of fetal death is 5-10% if the mother becomes infected.
    Disease, Fong: The nail-patella syndrome. This condition is sometimes called Fong disease for the physician who in 1946 discovered it in a patient on whom he performed intravenous pyelography while investigating hypertension and albuminuria related to pregnancy. On X-ray Dr. Fong saw the ‘iliac horns’ (symmetrical bilateral central posterior iliac processes) which are now known to be a characteristic feature of nail-patella syndrome.
    Disease, Forestier’s: A form of degenerative arthritis characteristically associated with flowing calcification along the sides of the vertebrae of the spine and commonly with inflammation (tendinitis) and calcification of the tendons at their attachments points to bone. Because areas of the spine and tendons can become inflamed, antiinflammatory medications (NSAIDs), such ibuprofen, can be helpful in both relieving pain and inflammation. Also called diffuse idiopathic skeletal hyperostosis (DISH).
    Disease, Gaucher’s type 1: A progressive genetic disease caused by a defect in an enzyme. The enzyme, called glucocerebrosidase, is needed to break down the chemical glucocerebroside. The enzyme defect in persons with Gaucher’s disease (GD) leads to the accumulation of glucocerebroside in the spleen, liver, and lymph nodes. The most common early sign is enlargement of the spleen (located in the upper left abdomen). Other signs include low red blood cell counts (anemia), a decrease in blood clotting cells (platelets), increased pigmentation of the skin, and a yellow fatty spot on the white of the eye (a pinguecula). Severe bone involvement can lead to pain and collapse of the bone of the hips, shoulders, and spine. The GD gene is on chromosome 1. The disease is a recessive trait. Both parents carry a GD gene and transmit it for their child with the disease. The parents’ risk of a child with the disease is 1 in 4 with each pregnancy. This type of Gaucher’s disease (noncerebral juvenile Gaucher’s disease) is most common in Ashkenazi Jews (of European origin) and is the most common genetic disease among Jews in the United States.
    Disease, graft-versus-host: A reaction of donated bone marrow against a patient’s own tissue. Also called GVHD.
    Disease, Graves’: The most common cause of hyperthyroidism (too much thyroid hormone), Graves’ disease is due to a generalized (diffuse) overactivity (toxic) of the whole enlarged thyroid gland (goiter); it is also commonly known as diffuse toxic goiter. There are three components to Graves’ disease: hyperthyroidism, protrusion of the eyes (ophthalmopathy), and skin lesions (dermopathy). Ophthalmopathy can cause sensitivity to light and a feeling of "sand in the eyes." With further protrusion of the eyes, double vision and vision loss may occur. The ophthalmopathy tends to worsen with smoking. Dermopathy of Graves’ disease is a rare, painless, reddish lumpy skin rash that occurs on the front of the leg. Graves’ disease can run in families. Factors that can trigger Graves’ disease include stress, smoking, radiation to the neck, medications (such as interleukin-2 and interferon-alpha), and infectious organisms such as viruses. Graves’ disease can be diagnosed by a typical thyroid scan (diffuse increase uptake), the characteristic triad of ophthalmopathy, dermopathy, and hyperthyroidism, or blood testing for TSI (Thyroid Stimulating Immunoglobulin) level which is abnormally high.
    Disease, gum: Inflammation of the soft tissue (gingiva) and abnormal loss of bone that surrounds the teeth and holds them in place. Gum disease is caused by toxins secreted by bacteria in "plaque" that accumulate over time along the gum line. This plaque is a mixture of food, saliva, and bacteria. Early symptoms of gum disease include gum bleeding without pain. Pain is a symptom of more advanced gum disease as the loss of bone around the teeth leads to the formation of gum pockets. Bacteria in these pockets cause gum infection, swelling, pain, and further bone destruction. Advanced gum disease can cause loss of otherwise healthy teeth.
    Disease, hemolytic, of the newborn: Abnormal breakup of red blood cells in the fetus or newborn.
    Disease, Hirschsprung’s: Absence of nerves (ganglia) in the bowel wall starting in the anus extending up a variable distance with enlargement of the bowel above that point. Hirschsprung’s disease is the commonest cause of lower intestinal obstruction in the newborn and, later, one of the causes of chronic constipation. Also called congenital aganglionic megacolon.
    Disease, His: Named for the Swiss physician Wilhelm His, Jr. (who also described the bundle of His in the heart), this is a louse-borne disease first recognized in the trenches of World War I (and so called trench fever), again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Also called Wolhynia fever, shin bone fever, quintan fever, five-day fever, Meuse fever, His-Werner disease, Werner-His disease.
    Disease, His-Werner: Named for the Swiss physician Wilhelm His, Jr. (who also described the bundle of His in the heart) and the German physician Heinrich Werner (who did not describe Werner’s syndrome). See Disease, His.
    Disease, Hodgkin’s (adult): A type of lymphoma (cancer of the lymphatic system). The most common symptom is painless swelling of the lymph nodes in the neck, underarm, or groin. Hodgkin’s disease is diagnosed when abnormal tissue is detected by a pathologist after a biopsy of an enlarged lymph node. Treatment usually includes radiation therapy or chemotherapy. Regular follow-up examinations are important after treatment. Patients treated for Hodgkin’s disease have an increased risk of developing other types of cancer later in life, especially leukemia.
    Disease, Hodgkin’s (Hodgkin’s lymphoma): A disease of the lymph nodes named after the English physician Thomas Hodgkin (1798-1866) who discovered it. ("Perfecting the World" is an excellent biography of Dr. Hodgkin by A. M. and E. H. Kass).
    Disease, Huntington’s: An hereditary disorder with mental and physical deterioration leading to death. Although characterized as an "adult-onset" disease (as is usually the case), we have seen children with full-blown Huntington’s disease.
    Disease, Jakob-Creutzfeldt: A transmissible degenerative brain disorder technically termed spongiform encephalopathy. Eating "mad cow" meat or squirrel brain can lead to Jakob-Creuzfeldt-like disease. Better known as Creutzfeldt-Jakob disease (CJD). A dementing disease of the brain, believed due to an unconventional, transmissible agent (a prion). Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome, Jakob’s disease, and spastic pseuodoparalysis.
    Disease, Jakob’s: Better known as Creutzfeldt-Jakob disease (CJD), a dementing disease of the brain. It is believed due to an unconventional, transmissible agent (a prion). Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome, Jakob-Creutzfeldt disease, and spastic pseuodoparalysis.
    Disease, Kawasaki’s: A syndrome of unknown origin, mainly affecting young children, causing fever, reddening of the eyes (conjunctivitis), lips and mucous membranes of the mouth, ulcerative gum disease (gingivitis), swollen glands in the neck (cervical lymphadenopathy), and a rash that is raised and bright red (maculoerythematous) in a glove-and-sock fashion over the skin of the hands and feet which becomes hard, swollen (edematous), and peels off. Also called mucocutaneous lymph node syndrome.
    Disease, Keshan: Condition caused by deficiency of the essential mineral selenium. Keshan disease is a potentially fatal form of cardiomyopathy (disease of the heart muscle). It was first observed in Keshan province in China and since has been found elsewhere (including New Zealand and Finland) in areas where the selenium level in the soil is low.
    Disease, kissing: Infectious mononucleosis ("mono"), a very common illness caused by the Epstein-Barr virus (EBV). By the time most people reach adulthood, an antibody against EBV can be detected in their blood meaning they have been infected with EBV. The illness is less severe in young children. The infection can be spread by saliva. Hence, the name: the kissing disease. The incubation period for "mono" is 4 to 8 weeks. Symptoms include fever, fatigue, sore throat, and swollen lymph glands. "Mono" can cause liver inflammation (hepatitis) and spleen enlargement. Vigorous contact sports should be avoided to prevent spleen rupture.
    Disease, Legg: See Disease, Legg-Perthes.
    Disease, Legg-Calve-Perthes: See Disease, Legg-Perthes.
    Disease, Legg-Perthes: A hip disorder in children due to interruption of the blood supply to the head of the femur (the ball in the ball-and-sockethip joint). Also called Legg disease and Legg-Calve-Perthes disease.
    Disease, Legionaire’s: A disease (first identified at the 1976 American Legion convention) due to bacteria (Legionella) found in plumbing, shower heads and water-storage tanks. Outbreaks of Legionella pneumonia have been attributed to evaporative condensors and cooling towers. Legionaire’s disease causes a cough, often non-productive, with fevers and a general sense of feeling unwell. Blood testing for antibodies to the bacteria and sputum analysis can aid in the diagnosis of Legionaire’s disease.
    Disease, lipid storage: A series of disorders due to inborn errors in lipid metabolism resulting in the abnormal accumulation of lipids in the wrong places (Examples include Gaucher, Fabry and Niemann-Pick diseases and metachromatic leukodystrophy).
    Disease, manic-depressive: See Manic-depression.
    Disease, maple syrup urine (MSUD): Hereditary disease due to deficiency of an enzyme involved in amino acid metabolism, characterized by urine that smells like maple syrup.
    Disease, mitochondrial: Mutations (changes) in the mitochondrial chromosome are responsible for a number of disorders including an eye disease (Leber’s hereditary optic atrophy), a type of epilepsy (called MERRF which stands for Myoclonus Epilepsy with Ragged Red Fibers), and a cause of dementia (called MELAS for Mitochondrial Encephalopathy, Lactic Acidosis and Stroke-like episodes). All mitochondrial diseases were entirely enigmatic before it was discovered that they were due to mutations not in regular chromosomes but the mitochondrial chromosome.
    Disease, ovarian, polycystic: See Disease, polycystic ovarian.
    Disease, polycystic ovarian (PCO): An hormonal problem that causes women to have a variety of symptoms including irregular or no periods, acne, obesity and excessive hair growth. Women with PCO are at a higher risk for uterine cancer (endometrial cancer), diabetes, high blood pressure, and heart disease. With proper treatment, risks can be minimized. PCO is also known as Stein-Leventhal syndrome.
    Diseases, polygenic: Genetic disorders that are caused by the combined action of more than one gene. Examples of polygenic conditions include hypertension, coronary heart disease, diabetes, and peptic ulcers. Because such disorders depend on the simultaneous presence of several genes, they are not inherited as simply as single-gene diseases.
    Disease, Ritter: This is the scalded skin syndrome, a potentially serious side effect of infection with the Staph (Staphylococcus) bacteria that produces a specific protein which loosens the "cement" holding the various layers of the skin together. This allows blister formation and sloughing of the top layer of skin. If it occurs over large body regions it can be deadly (just like a large surface area of the body having been burned). It is necessary to treat scalded skin syndrome with intravenous antibiotics and to protect the skin from allowing dehydration to occur if large areas peel off. The disease occurs predominantly in children under 5 years of age. It is known formally as Staphyloccoccal scalded skin syndrome.
    Disease, sixth: A viral disease of infants and young children with sudden onset of high fever which lasts several days and then suddenly subsides leaving in its wake a fine red rash. The causative agent is herpesvirus type 6 so the disease is known as Sixth Disease. Also known as Exanthem subitum (sudden rash), Pseudorubella, Roseola, Roseola infantilis, and Roseola infantum.
    Disease, Stein-Leventhal: See Disease, polycystic ovarian.
    Disease, Still’s: Also known as systemic-onset juvenile rheumatoid arthritis and systemic-onset juvenile chronic arthritis. Still’s disease presents with systemic (bodywide) illness including high intermittent fever, a salmon-colored skin rash, swollen lymph glands, enlargement of the liver and spleen, and inflammation of the lungs (pleuritis) and around the heart (pericarditis). The arthritis may not be immediately apparent but it persists after the systemic symptoms are gone. Disease, Still’s, adult-onset: Although Still’s disease was first described in children, it is known to occur in adults.
    Disorders, myeloproliferative: Tumors of certain bone marrow cells including those that give rise to red cells, granulocytes, and platelets. As opposed to the lymphoproliferative disorders.
    Disease, Paget’s: A condition of unknown cause in which the bone formation is out of synchrony with normal bone remodeling.
    Disease, Parkinson’s: An abnormal condition of the nervous system caused by degeneration of an area of the brain called the basal ganglia. The disease results in rigidity of the muscles, slow body movement and tremor. Parkinson’s disease is also called "paralysis agitans" and "shaking palsy."
    Disease, Parry’s: Toxic multinodular goiter, a condition in which the thyroid gland contains multiple lumps (nodules) that are overactive and produce excess thyroid hormones. This condition is also known as Plummer’s disease.
    Disease, Plummer’s: Toxic multinodular goiter, a condition in which the thyroid gland contains multiple lumps (nodules) that are overactive and produce excess thyroid hormones. This condition is also known as Parry’s disease.
    Disease, pelvic inflammatory (PID): Despite its seeming lack of gender, this term is applied to women only. PID refers exclusively to ascending infection of the female genital tract above the cervix.
    Disease, phytanic acid storage (Refsum’s disease): A genetic disorder of the fatty acid phytanic acid which accumulates and causes a number of progressive problems including polyneuritis (inflammation of numerous nerves), diminishing vision (due to retinitis pigmentosa), and wobbliness (ataxia) caused by damage to the cerebellar portion of the brain (cerebellar ataxia).
    Disease, Pick’s: A form of dementia characterized by a slowly progressive deterioration of social skills and changes in personality leading to impairment of intellect, memory, and language.
    Disease, polycystic kidney: Genetic (inherited) disorders characterized by the development of innumerable cysts in the kidneys filled with fluid that replace much of the mass of the kidneys and reduce kidney function leading to kidney failure.
    Disease, polycystic ovarian: A hormonal problem that causes women to have a variety of symptoms including irregular or no periods, acne, obesity and excessive hair growth. Also known as Stein-Leventhal syndrome.
    Disease, Quincke’s: This is angioneurotic edema (or angioedema), a form of localized swelling of the deeper layers of the skin and fatty tissues beneath the skin. Hereditary angioneurotic edema (or hereditary angioedema) is a genetic form of angioedema. Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks.
    Disease, Refsum’s: A genetic disorder of the fatty acid phytanic acid which accumulates and causes a number of progressive problems including polyneuritis (inflammation of numerous nerves), diminishing vision (due to retinitis pigmentosa), and wobbliness (ataxia) caused by damage to the cerebellar portion of the brain (cerebellar ataxia).
    Disease, Tsutsugamushi: Scrub typhus, a mite-borne infectious disease caused by a microorganism, Rickettsia tsutsugamushi, characteristically with fever, headache, a raised (macular) rash, swollen glands (lymphadenopathy) and a dark crusted ulcer (called an eschar or tache noire) at the site of the chigger (mite larva) bite. This disease occurs in the area bounded by Japan, India, and Australia. Known also as mite-borne typhus and tropical typhus.
    Diseases, rickettsial: The infectious diseases caused by the rickettsiae fall into 4 groups:(1) typhus: epidemic typhus, Brill-Zinsser disease, murine (endemic) typhus, and scrub typhus; (2) spotted fever—Rocky Mountain spotted fever, Eastern tick-borne rickettsioses, and rickettsialpox; (3) Q fever; and (4) trench fever.
    Diseases, single-gene: Hereditary disorders caused by a change (mutation) in a single gene. There are thousands of single-gene diseases including achondroplastic dwarfism, Huntington disease, cystic fibrosis, sickle cell disease, Duchenne muscular dystrophy, and hemophilia. Single-gene diseases typically describe classic simple Mendelian patterns of inheritance (as autosomal dominant, autosomal recessive, and X-linked traits) by comparison with polygenic diseases.
    Disease, von Recklinghausen’s: Hereditary disorder characterized by cafe-au-lait (coffee-with-milk spots on the skin and a tendency to develop nerve tumors) also known as neurofibromatosis.
    Disease, Werner-His: Named for the German physician Heinrich Werner (who did not describe Werner’s syndrome) and the Swiss physician Wilhelm His, Jr. (who did describe the bundle of His in the heart), this is a louse-borne disease first recognized in the trenches of World War I (and so called trench fever), again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash.
    Recovery takes a month or more. Relapses are common. Also called Wolhynia fever, shin bone fever, quintan fever, five-day fever, Meuse fever, His-Werner disease.
    DISH: Acronym for Diffuse Idiopathic Skeletal Hyperostosis, a form of degenerative arthritis characteristically associated with flowing calcification along the sides of the vertebrae of the spine and, commonly, inflammation (tendinitis) and calcification of the tendons at their attachments points to bone. Because areas of the spine and tendons can become inflamed, antiinflammatory medications (NSAIDs), such ibuprofen, can be helpful in both relieving pain and inflammation. Also called Forestier’s disease.
    Disruption sequence: The events that occur when a fetus that is developing normally is subjected to a destructive agent such as the rubella (German measles) virus.
    Diverticula: The plural of diverticulum. As a person ages, pressure within the large intestine (colon) causes pockets of tissue (sacs) that push out from the colon walls. A small bulging sac pushing outward from the colon wall is a diverticulum. Diverticula can occur throughout the colon but are most common near the end of the left side of the colon, the sigmoid colon.
    Diverticulitis: Inflammation of diverticula (small bulging sacs pushing outward from the colon wall). Can be diagnosed with barium x-rays or with sigmoidoscopy or colonoscopy.
    Diverticulitis, bleeding from: Diverticular bleeding typically occurs intermittently over several days. Colonoscopy is usually performed to confirm the diagnosis and exclude bleeding from other causes. Thermal probes cannot be employed to stop active diverticular bleeding. Therefore, surgical removal of the bleeding diverticula is necessary for those with persistent bleeding.
    Diverticulitis, treatment of acute: Antibiotics are usually needed. Oral antibiotics are sufficient when symptoms are mild. Liquid or low fiber foods are advised during acute diverticulitis attacks. In severe diverticulitis with high fever and pain, patients are hospitalized and given intravenous antibiotics. Surgery is needed for persistent bowel obstruction or abscesses not responding to antibiotics.
    Diverticulosis: A small bulging sac pushing outward from the colon wall is called a diverticulum. (Two or more such sacs are diverticula). Diverticula can occur throughout the colon. The condition of having these diverticula in the colon constitutes diverticulosis. associated with inflammation and infection, the condition is called diverticulitis. While most patients with diverticulosis have few or no symptoms. diverticulosis symptoms can include abdominal cramping, constipation, diarrhea, bloating.
    Diverticulosis/diverticulitis and fiber: High fiber diets help delay the progression of diverticulosis and, at least, reduce the bouts of diverticulitis.
    Diverticulum: A small bulging sac pushing outward from the colon wall is a diverticulum. As a person ages, pressure within the large intestine (colon) causes pockets of tissue (sacs) that push out from the colon walls. The plural is diverticula. Diverticula can occur throughout the colon but are most common near the end of the left side of the colon, the sigmoid colon.
    Dizygotic twins: Dizygotic twins are siblings who have shared a common uterine environment. They are due to fertilization of two different ova by different sperm. Dizygotic twins are also called fraternal twins.
    Dizziness: Feelings such as lightheadedness, giddiness, depersonalization (the feeling that one is outside ones body), a sense of turning, spinning or rocking. Sometimes a sensation inside the head and other times related to problems with balance.
    Dizziness, anxiety as a cause of: One cause of dizziness is overbreathing (hyperventilation) due to anxiety. The overbreathing also causes lightheadedness, a sense of unsteadiness and tingling around the mouth and fingertips. Relief can be gotten by breathing in and out of a paper bag (to increase the level of carbon dioxide in the blood).
    Dizziness, pre-syncopal: Syncope is fainting. Pre-syncope is before fainting, whedn one is about to faint. Some symptoms of dizziness such as wooziness, feeling about to black out, and tunnel vision may be pre-syncopal and are due to insufficient blood flow to the brain. These symptoms are typically worse when standing, improve with lying down and may be experienced by healthy individuals who rise quickly from a chair, often after a meal, and have a few seconds of disorientation.
    DNA (deoxyribonucleic acid): The molecule that encodes the genetic information. DNA is a double-stranded molecule that is held together by weak bonds between base pairs of nucleotides to form a double helix. The four nucleotides in DNA contain the bases: adenine (A), guanine (G), cytosine ©, and thymine(T). Base pairs form naturally only between A and T and between G and C so the base sequence of each single strand of DNA can be simply deduced from that of its partner strand. The code is in triplets such as ATG. The base sequence of that triplet in the partner strand is therefore TAC.
    DNA cloning: The use of DNA manipulation procedures to produce multiple copies of a single gene or segment of DNA.
    DNA molecules, recombinant: A combination of DNA molecules of different origin that are joined using recombinant DNA technology.
    DNA, nongenetic: Through the marvellous medium of the Internet, we have discovered that DNA need not refer to deoxyribonucleic acid. Specifically, in an e-mail entitled " A day in the life of a specialist registrar" from Glascow, Scotland we read that in gynaecology outpatient clinic, the specialist registrar (resident in the U.S.) at "12:10 Sorted out the DNA’s (did not attends)." We in the U. S. might say the "no-show" when a patient does not present for his/her appointment.
    DNA polymerase: Enzyme that catalyzes (speeds) the polymerization of DNA. DNA polymerase uses preexisting nucleic acid templates and assembles the DNA from deoxyribonucleotides.
    DNA repair: The cell has a series of special enzymes to repair mutations (changes) in the DNA and restore the DNA to its original state.
    DNA repair gene: A gene engaged in DNA repair. When a DNA repair gene is altered, mutations pile up throughout the DNA.
    DNA repair pathway: The sequence of steps in the repair of DNA. Each step is governed by an enzyme.
    DNA, repetitive: DNA sequences that are repeated in the genome.
    DNA replication: A wondrous complex process whereby the ("parent") strands of DNA in the double helix are separated and each one is copied to produce a new ("daughter") strand. This process is said to be "semi-conservative" since one of each parent strand is conserved and remains intact after replication has taken place.
    DNA, satellite: DNA that contains many tandem (not inverted) repeats of a short basic repeating unit. Satellite DNA is located at very specific spots in the genome (on chromosomes 1, 9, 16 and the Y chromosome, the tiny short arms of chromosomes 13-15 and 21 and 22, and near the centromeres of chromosomes).
    DNA sequence: The precise ordering of the bases (A,T,G,C) from which the DNA is composed.
    DNA technology, recombinant: A series of procedures used to join together (recombine) DNA segments. A recombinant DNA molecule is constructed (recombined) from segments from 2 or more different DNA molecules. Under certain conditions, a recombinant DNA molecule can enter a cell and replicate there, autonomously (on its own) or after it has become integrated into a chromosome.
    DOE: Department of Energy, U.S. One of the agencies contributing to the Human Genome Project.
    Domain: In biomedicine, a domain is a discrete portion of a protein with its own function. The combination of domains in a single protein determines its overall function. (Not to be confused with an Internet domain.)
    Dominant : A trait that is expressed in a person when only one copy of a gene is present; as opposed to a recessive trait which is expressed only when two copies of a particular gene are present. Examples of dominantly-inherited disorders include achondroplasia (a common form of dwarfism), familial hypercholesterolemia (high blood cholesterol in families leading to premature coronary artery disease) and Huntington disease (a form of progressive dementia).
    Donor: The giver of a tissue or organ, for example, of blood or a kidney. Double helix: The structure of DNA with the two strands of DNA spiraling about each other. (The Double Helix is the title of a excellent book by James Watson telling the story of his and Francis Crick's discovery of the correct model for DNA).
    Dopa-Responsive Dystonia (DRD): A condition successfully treated with drugs. Typically, DRD begins in childhood or adolescence with progressive difficulty in walking and, in some cases, spasticity. Segawa’s dystonia is an important variant of DRD. In Segawa’s dystonia, the symptoms fluctuate during the day from relative mobility in the morning to increasingly worse disability in the afternoon and evening as well as after exercise. Some scientists feel DRD is not only rare but also rarely diagnosed since it mimics many of the symptoms of cerebral palsy.
    Dorsal: The back or posterior side of a structure.
    Double helix: The structure of DNA with the two strands of DNA spiraling about each other. (The Double Helix is the title of a excellent book by James Watson telling the story of his and Francis Crick's discovery of the correct model for DNA).
    Douching: Using water or a medicated solution to clean the vagina and cervix.
    Down syndrome: A common chromosome disorder due to an extra chromosome number 21 (trisomy 21). Down syndrome causes mental retardation, a characteristic face, and multiple malformations. It is associated with a major risk for heart problems, a lesser risk of duodenal atresia (part of the intestines not developed), and a minor but still significant risk of acute leukemia. The name Down syndrome comes from the 19th century English doctor Langdon Down. He was curiously enough not the first person to describe the condition, added little to knowledge and, in great error, attributed the condition to a "reversion" to the mongoloid race. The disorder was also once called mongolism, a term now considered slang.
    DPT: Diphtheria-Pertussis-Tetanus vaccine. Today the more frequent abbreviation is DTP ( for Diphtheria-Tetanus-Pertussis vaccine).
    DPT immunization: DPT immunization protects from diphtheria, pertussis (whooping cough), and tetanus and is given in a series of 5 shots at 2, 4, 6, 18 months of age and 4-6 years of age. Thanks to vaccination programs, these diseases have become less common. However, there are still unvaccinated individuals capable of carrying and passing diphtheria and pertussis to others who are not vaccinated. Tetanus bacteria are prevalent in natural surroundings, such as contaminated soil. See also DTaP immunization.
    Drug resistance: The ability of bacteria and other microorganisms to withstand a drug to which they were once sensitive (and were once stalled or killed outright).
    DT: Diptheria-Tetanus vaccine.
    DT immunization: DT (diphtheria and tetanus) vaccine does not protect from pertussis and is usually reserved for individuals who have had a significant adverse reaction to a DPT shot or who have a personal or family history of a seizure disorder or brain disease.
    DTaP: Diphtheria-Tetanus-acellular Pertussis vaccine.
    DTaP immunization: Like DPT, DTaP protects from diphtheria, pertussis (whooping cough) and tetanus. DTaP is the same as DTP, except that it contains only acellular pertussis vaccine which is thought to cause fewer of the minor reactions associated with immunization and is also probably less likely to cause the more severe reactions occasionally seen following pertussis vaccination. DTaP is currently recommended only for the shots given at 18 months and 4-6 years of age.
    DTP: Diphtheria-Tetanus-Pertussis vaccine.
    Ductus: A duct or walled passageway. Our word "duct" is a contraction of the Latin word "ductus" meaning "leading". The Romans, however, preferred the word "canalis" meaning "a pipe or gutter" for a conduit.
    Ductus arteriosus: Before birth, the blood headed from the heart (via the pulmonary artery) for the lungs is shunted away from the lungs and returned to the greatest of arteries (the aorta). The shunt is through a short vessel called the ductus arteriosus. When the shunt is open, it is said to be patent (pronounced pa’tent). The patent ductus arteriosus (PDA) usually closes at or shortly after birth and blood is permtted from that moment on to course freely to the lungs. If the ductus stays open (patent), flow reverses and blood from the aorta is shunted into the pulmonary artery and recirculated through the lungs. The PDA may close later spontaneously (on its own) or need to be ligated (tied off) surgically.
    Dumping syndrome: A group of symptoms that occur when food or liquid enters the small intestine too rapidly. These symptoms include cramps, nausea, diarrhea, and dizziness.
    Duodenal ulcer: An ulcer (a hole in the lining) of the duodenum (the first portion of the small intestine). Ulcers can affect the stomach, duodenum, or esophagus. Their formation is related to H. pyloridus bacteria in the stomach, anti-inflammatory medications, and smoking cigarettes. Ulcer pain may not correlate with the presence orseverity of ulceration. Diagnosis is made with barium x-ray or endoscopy. Complications of ulcers include bleeding, perforation, and blockage of the stomach (gastric obstruction). Treatment involves antibiotics to eradicate H. pyloridus, eliminating risk factors, and preventing complications.
    Duodenum: The first part of the small intestine. The duodenum is a common site for peptic ulcer formation.
    Duodenitis: Inflammation of the duodenum. (The duodenum is the first part of the small intestine.)
    Duplication: Part of a chromosome in duplicate. The opposite of a deletion.
    Dwarfism: Old term for short stature.
    Dysfunction, erectile: A consistent inability to sustain an erection sufficient for sexual intercourse. Also commonaly known as "impotence." Medically, the term "erectile dysfunction" is used to differentiate impotence from other problems that interfere with sexual intercourse (such as lack of sexual desire and problems with ejaculation and orgasm). Impotence usually has a physical cause, such as disease, injury, drug side-effects, or a disorder that impairs blood flow in the penis. Impotence is treatable in all age groups.
    Dyslexia: A specific reading disability due to a defect in the higher cortical processing of graphic symbols. Dyslexia is different from reading retardation which may, for example, reflect mental retardation or cultural deprivation.
    Dysmorphic feature: A body characteristic that is abnormally formed. A malformed ear, for example, is a dysmorphic feature.
    Dysmorphology: Term coined by the late Dr. David W. Smith for the study of malformations.
    Dyspareunia: The medical term for pain during sexual intercourse.
    Dysplasia: Abnormal in form. From the Greek dys- (bad, disordered, abnormal) and plassein (to form). For example, retinal dysplasia is abnormal formation of the retina during embryonic development.
    Dysplastic nevi: Atypical moles; moles whose appearance is different from that of common moles. Dysplastic nevi are generally larger than ordinary moles and have irregular borders. Their color often is not uniform; they usually are flat, but parts may be raised above the skin surface.
    Dysphonia, spasmodic: Involves the muscles of the throat that control speech. Also called spastic dysphonia or laryngeal dystonia, it causes strained and difficult speaking or breathy and effortful speech.
    Dyspnea: Apparent breathing distress usally a result of serious disease of the heart, lungs, or airways.
    Dyspraxia: Impaired or painful function of any organ of the body.
    Dysthymia: A type of depression involving long- term, chronic symptoms that do not disable you, but keep you from functioning at "full steam" or from feeling good. Dysthymia is a less severe type of depression than what is considered a major depression. However, people with dysthymia may also sometimes experience major depressive episodes.
    Dystonia: Involuntary movements and prolonged muscle contraction, resulting in twisting body motions, tremor, and abnormal posture. These movements may involve the entire body, or only an isolated area. Symptoms may even be "task specific," such as writer’s cramp. Dystonia can be inherited, occur sporadically without any genetic pattern, or be associated with medications or diseases (for example, a specific form of lung cancer). The gene responsible for at least one form of dystonia has recently been identified. Some types of dystonia respond to dopamine, or can be controlled with sedative-type medications, or surgery.
    Dystonia, cranial: A term used to describe dystonia that affects the muscles of the head, face, and neck. Oromandibular dystonia affects the muscles of the jaw, lips, and tongue. The jaw may be pulled either open or shut, and speech and swallowing can be difficult. Spasmodic dysphonia involves the muscles of the throat that control speech. Also called spastic dysphonia or laryngeal dystonia, it causes strained and difficult speaking or breathy and effortful speech. Meige’s syndrome is the combination of blepharospasm and oromandibular dystonia and sometimes spasmodic dysphonia. Spasmodic torticollis can be classified as a type of cranial dystonia.
    Dystonia, dopa-responsive (DRD): A condition successfully treated with drugs. Typically, DRD begins in childhood or adolescence with progressive difficulty in walking and, in some cases, spasticity. Segawa’s dystonia is an important variant of DRD. In Segawa’s dystonia, the symptoms fluctuate during the day from relative mobility in the morning to increasingly worse disability in the afternoon and evening as well as after exercise. Some scientists feel DRD is not only rare but also rarely diagnosed since it mimics many of the symptoms of cerebral palsy.
    Dystonia, focal, due to blepharospasm: The second most common focal dystonia, the involuntary, forcible closure of the eyelids. The first symptoms may be uncontrollable blinking. Only one eye may be affected initially, but eventually both eyes are usually involved. The spasms may leave the eyelids completely closed causing functional blindness even though the eyes and vision are normal.
    Dystonia, focal, due to torticollis: Spasmodic torticollis, or torticollis, is the most common of the focal dystonias. In torticollis, the muscles in the neck that control the position of the head are affected, causing the head to twist and turn to one side. In addition, the head may be pulled forward or backward.
    Dystonia, idiopathic torsion: A form of dystonia known as early-onset torsion dystonia (also called generalized torsion dystonia) begins in childhood around the age of 12. Symptoms typically start in one part of the body, usually in an arm or leg, and eventually spread to the rest of the body within about 5 years. Early-onset torsion dystonia is not fatal, but it can be severely debilitating.
    Dystonia, oromandibular: Oromandibular dystonia affects the muscles of the jaw, lips, and tongue. The jaw may be pulled either open or shut, and speech and swallowing can be difficult.
    Dystonia, Segawa’s: An important variant of dopa-responsive dystonia (DRD), a condition successfully treated with drugs. Typically, DRD begins in childhood or adolescence with progressive difficulty in walking and, in some cases, spasticity. In Segawa’s dystonia, the symptoms fluctuate during the day from relative mobility in the morning to increasingly worse disability in the afternoon and evening as well as after exercise.
    Dystonia, torsion: A form of dystonia known as early-onset torsion dystonia (also called idiopathic or generalized torsion dystonia) begins in childhood around the age of 12. Symptoms typically start in one part of the body, usually in an arm or leg, and eventually spread to the rest of the body within about 5 years. Early-onset torsion dystonia is not fatal, but it can be severely debilitating. Most children with the disorder are unable to perform the simplest of motor tasks and are confined to a wheelchair by the time they reach adulthood.
    Dystonia, writer’s cramp: A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs during handwriting. Similar focal dystonias have also been called typist’s cramp, pianist’s cramp, musician’s cramp, and golfer’s cramp.
    Dystrophy, myotonic: Inherited disease with myotonia (irritability and prolonged contraction of muscles), mask-like face, premature balding, cataracts, and cardiac disease. Due to a trinucleotide repeat (a stuttering sequence of three bases) in the DNA.
    Dysuria: Pain on urination, or difficulty urinating.
  • Ear: The hearing organ. There are three sections of the ear, according to the anatomy textbooks. They are the outer ear (the part we see along the sides of our head behind the temples), the middle ear, and the inner ear. But in terms of function, the ear has four parts: those three and the brain.
    Ear canal, self-cleaning: Most of the time the ear canals are self-cleaning, that is, there is a slow and orderly migration of ear canal skin from the eardrum to the outer opening. Old earwax is constantly being transported from the deeper areas of the ear canal to the opening where it usually dries, flakes, and falls out.
    Ear cleaning (by a doctor): When so much wax accumulates that it blocks the ear canal (and hearing), your physician may have to wash it out, vacuum it, or remove it with special instruments. Alternatively, your physician may prescribe ear drops what are designed to soften the wax (such as Cerumenex).
    Ear cleaning (yourself): Never put anything smaller than your elbow in your ear! Wax is not formed in the deep part of the ear canal near the eardrum, but only in the outer part of the canal. So when a patient has wax pushed up against the eardrum, it is often because he has been probing his ear with such things as cotton-tipped swabs (such as Q-Tips), bobby pins, or twisted napkin corners. Such objects only serve as ramrods to push the wax in deeper. Also, the skin of the ear canal and the eardrum is very thin, fragile and easily injured. The ear canal is more prone to infection after it has been whipped clean of the "good" coating type wax. In addition, we have seen many perforated eardrums as a result of these efforts.
    Ear, low-set: A minor anomaly involving an ear situated down below its normal location. Technically, the ear is low-set when the helix (of the ear) meets the cranium at a level below that of a horizontal plane through both inner canthi (the inside corners of the eyes). The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Ear, malrotated: See Ear, slanted.
    Ear pit: Tiny pit in front of the ear: preauricular pit. A minor anomaly of no great consequence in itself. More common in blacks than whites and in females than males. Can recur in families. The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Ear puncture: Puncture of the ear drum may be due to an accident for example when something is stuck into the ear. Or it may be due to fluid pressure in the middle ear. Today the ear drum is occasionally punctured on purpose with surgery. A surgically placed tiny incision (a myringotomy) is made in the eardrum. Any fluid, usually thickened secretions, is removed and an ear tube may be inserted.
    Ear ringing: Together with other abnormal ear noises, ear ringing is medically called tinnitis. Tinnitus can arise in any of the four sections of the ear: the outer ear, the middle ear, the inner ear, and the brain. If tinnitus persists and its cause is unknown, a hearing test (audiogram) should be done. Measures can be taken to lessen the intensity of tinnitus.
    Ear, slanted: An ear that is slanted more than usual. Technically, an ear is slanted when the angle of the slope of the auricle is more than 15 degrees from the perpendicular. Also called a malrotated ear Considered a minor anomaly. The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Ear tag: Common minor anomaly, a rudimentary tag of ear tissue, often containing a core cartilage, usually located just in front of the ear (auricle). Therefore also called preauricular tag. The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Ear tubes: Formally known as tympanostomy tubes, ear tubes are small plastic tubes inserted into the eardrum (the tympanum) to keep the middle ear aerated for a prolonged period of time. To put the tubes in place, a myringotomy (a surgically placed tiny incision in the eardrum) is done. Any fluid, usually thickened secretions, will be removed. The ear tubes usually remain in place for 6 months to several years. Water should not be allowed to enter the ear canal while the tubes are in place. Eventually, they will move out of the eardrum (extrude) and fall into the ear canal. The doctor may remove the tube during a routine future office visit or it may simply fall out of the ear without the child realizing it.
    Ear wax: The ear canal is shaped somewhat like an hourglass. The skin on the outer part of the canal has special glands that produce earwax. The purpose of this natural wax is to repel water and to trap dust and sand particles. Usually a small amount of wax accumulates, and then dries up and falls out of the ear canal caring with it unwanted particles. Ear wax is helpful in normal amounts and serves to coat the skin of the ear canal where it acts as a temporary water repellent. The absence of ear wax may result in dry, itchy ears, and even infection.
    Eardrum: The tympanic membrane of the ear.
    EBV: The Epstein-Barr virus which can cause infectious mononucleosis ("mono").
    ECG: Abbreviation for electrocardiogram. Abbreviation for electrocardiogram. The K is from "kardio" (in German).
    Ecchymosis: The skin discoloration caused by a bruise (contusion).
    Ecchymotic: Characterized by ecchymosis.
    Echocardiography: Echocardiography is a diagnostic test which uses ultrasound waves to make images of the heart chambers, valves and surrounding structures. It can measure cardiac output and is a sensitive test for inflammation around the heart (pericarditis). It can also be used to detect abnormal anatomy or infections of the heart valves.
    Echovirus: One of a group of viruses.
    E. coli: Short for Escherichia coli, the colon bacillus, a bacterium that normally resides in the human colon. E. coli has been studied intensively in genetics and molecular and cell biology because of its availability, its small genome size, its normal lack of pathogenicity (disease-causing ability), and its ease of growth in the laboratory.
    Ecogenetics: The interaction of genetics with the environment. The genetic disease PKU (phenylketonuria) provides an illustration of ecogenetics. Persons with PKU lack an enzyme to process an amino acid (phenylalanine) and so require a special environment: a diet low in phenylalanine.
    Ectopia cordis: A type of birth defect resulting in an abnormal location of the heart. (Most often, in individuals with ectopia cordis, the heart protrudes outside the chest.)
    Ectopic: In the wrong place. An ectopic kidney, for example, is one that is not in the usual location.
    Ectopic pregnancy: A pregnancy that is not in the usual place and is located outside the inner lining of the uterus. A fertilized egg settles and grows in any location other than the inner lining of the uterus. The vast majority of ectopic pregnancies occur in the fallopian tube (95%), however, they can occur in other locations, such as the ovary, cervix, and abdominal cavity. An ectopic pregnancy occurs in about 1 in 60 pregnancies. A major concern with an ectopic pregnancy is internal bleeding. If there is any doubt, seek medical attention promptly.
    Ectopic pregnancy, symptoms of: Symptoms of an ectopic pregnancy can often be vague and include vaginal bleeding, abdominal or pelvic pain (usually stronger on one side),shoulder pain, weakness, or dizziness. Weakness, dizziness, and a sense of passing out upon standing can represent serious internal bleeding, requiring immediate medical attention.
    Eczema: A particular reaction pattern of the skin, the most common type in children being atopic (allergic) dermatitis.
    Edema: Edema is the swelling of soft tissues as a result of excess water accumulation. It is often more prominent in the lower legs and feet toward the end of the day as a result of pooling of fluid from the upright position maintained during the day. Upon awakening from sleeping, patients can have swelling around the eyes referred to as "periorbital edema."
    Edema, hereditary angioneurotic: A genetic form of angioedema. (Angioedema is also referred to as Quinke’s disease.) Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks. Also called hereditary angioedema.
    Edwards syndrome: This is trisomy 18 syndrome. There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is profound with the IQ too low to edven test. Nineteen out of 20 (95%) of these children die before their first birthday. The condition is named after the British physician and geneticist John Edwards who discovered the extra chromosome in 1960.
    EGD (esophagogastroduodenoscopy): A procedure that enables the examiner (usually a gastroenterologist ) to examine the esophagus ( swallowing tube), stomach, and duodenum ( first portion of small bowel ) using a thin flexible tube (a "scope") that can be looked through or seen on a TV monitor. Also called upper endoscopy
    Egg: Ovum (plural: ova).
    Ehrlichiosis: An acute (abrupt-onset) disease (first reported in humans in 1986) due to infection by the rickettsial agent, Ehrlichia canis. The brown dog tick, is the common vector (carrier). The disease is similar to Rocky Mountain spotted fever with high fever, headache, malaise, and muscle pain but no rash. Named for the great German Nobel Prize winning physician and bacteriologist Paul Ehrlich (1854-1915).
    Ejaculation: Ejection of sperm and seminal fluid.
    Elbow: The joint where three long bones meet in the middle portion of the arm. The bone of the upper arm (humerus) meets the inner bone of the forearm (ulna) and the outer bone of the forearm (radius) to form a hinge joint. The radius and ulna also meet in the elbow to allow for rotation of the forearm. The elbow functions to move the arm like a hinge (forward and backward) and in rotation (twisting outwards and inwards). The biceps muscle is the major muscle that flexes the elbow hinge. The triceps muscle is the major muscle that extends the elbow hinge. The outer bone of the elbow is the lateral epicondyle and is a part of the humerus bone. Tendons are attach to this area which can be injured, causing inflammation or tendinitis (lateral epicondylitis, or "tennis elbow"). The inner portion of the elbow is a bony prominence called the medial epicondyle. Additional tendons from the muscles attach here and can be injured, causing medial epicondylitis, "golfer’s elbow."
    Elbow, arthritis of the: Inflammation (arthritis) of the elbow joint can be due to many systemic forms of arthritis, including rheumatoid arthritis, gouty arthritis, psoriatic arthritis, ankylosing spondylitis, and Reiter’s disease. Generally, they are associated with signs of inflammation of the elbow joint, including heat, warmth, swelling, pain, tenderness, and decreased range of motion. Range of motion of the elbow is decreased with arthritis of the elbow because the swollen joint impedes the range of motion
    Elbow bursitis: At the tip of the elbow (the olecranon area), there is a bursa, a fluid-filled sac that functions as a gliding surface to reduce friction with motion. This bursa is known as the olecranon bursa. Because of its location, the olecranon bursa is subject to trauma, ranging from simple repetitive weight bearing while leaning, to banging in a fall. This trauma can cause a common, aseptic form of bursitis (olecranon bursitis) with varying degrees of swelling, warmth, tenderness and redness in the area overlying the point of the elbow.
    Elbow bursitis, treatment of: If non-infectious, elbow bursitis treatment includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery.
    Elbow, cellulitis of the: Inflammation of the skin around the elbow due to infection (cellulitis) commonly occurs as a result of abrasions or puncture wounds permitting bacteria on the surface of the skin to invade the deeper layers of the skin. This causes inflamed skin characterized by heat, redness, warmth, and swelling. The most common bacteria that cause cellulitis include Staphylococcus ("Staph") and Streptococcus ("Streop"). One can have an associated low-grade fever. Cellulitis generally requires antibiotic treatment, either orally or intravenously. Heat application can help in the healing process.
    Elbow, golfer’s: The inner portion of the elbow is a bony prominence called the medial epicondyle. Tendons from the muscles attach here and can be injured, causing medial epicondylitis. To those who play the ancient Scottish sport, this is "golfer’s elbow."
    Elbow pain: The elbow joint is quite complex because it is the area of union of three long bones. Elbow pain has many causes including arthritis and bursitis. Tendinitis can affect the inner or outer elbow; the treatment includes ice, rest, and medication for inflammation. Bacteria can also infect the skin of the scraped (abraded) elbow. The "funny bone" nerve can be irritated at the elbow to cause numbness and tingling of the little and ring fingers.
    Elbow, tennis: The outer bone of the elbow is the lateral epicondyle and is a part of the humerus bone. Tendons are attach to this area which can be injured, causing inflammation or tendinitis (lateral epicondylitis). This is known to tennis players as "tennis elbow".
    Electrocardiogram: A recording of the electrical activity of the heart. To take a specific situation, the initial diagnosis of a heart attack is usually made by a combination of clinical symptoms and characteristic electrocardiogram (EKG) changes. The EKG can detect areas of muscle ischemia (muscle deprived of oxygen) and/or dead tissue in the heart.
    Electrodesiccation: Use of an electric current to destroy cancerous tissue and control bleeding.
    Electrolarynx: A battery-operated instrument that makes a humming sound to help laryngectomees talk.
    Electrolyte: An electrolyte is a substance that will dissociate into ions in solution and acquire the capacity to conduct electricity. The electrolytes include sodium, potassium, chloride, calcium and phosphate. Informally, called lytes. (The clue to the word electrolyte is in the lyte which comes from the Greek lytos meaning that may be dissolved.)
    Electron microscope: Microscope that uses electron beams rather than light beams to provide a magnified image of tiny particles. The electron microscope is more powerful than the light microscope and in some diseases can provide detailed images that lead to the diagnosis of specific conditions.
    Electron microscopy (EM): A microscope in which electron beams replaceslight rays to form the image. EM has its pluses (greater magnification and resolution than optical microscopes) and minuses (you are not really "seeing" objects, but rather their electron densities, and artefacts often abound). Despite such limitations, EM has greatly extended the powers of the microscope.
    Electrophoresis: Method used in clinical and research laboratories for separating molecules according their size and electrical charge. Electrophoresis is used to separate large molecules (such as DNA fragments or proteins) from a mixture of molecules. An electric current is passed through a medium containing the mixture of molecules. Each kind of molecule travels through the medium at a different rate, depending on its electrical charge and molecular size. Separation of the molecules is based on these differences. Although many substances including starch gels and paper have historically served as media for electrophoresis, agarose and acrylamide gels are the media commonly used for electrophoresis of proteins and nucleic acids.
    Elliptocytosis: Hematologic disorder characterized by elliptically shaped red blood cells (elliptocytosis) with variable breakup of red cells (hemolysis) and varying degrees of anemia. Inherited as a dominant trait. Due to mutation (change) in one of the genes encoding proteins of the red cell membrane skeleton. In 1956 Newton Morton brilliantly showed that there were at least 2 forms of elliptocytosis, one form unlinked to the Rh blood group and another form linked to Rh (now known to be on chromosome 1). The Rh-linked form, (EL1) in chromosome region 1p34.2-p33 is due to a mutation in erythrocyte membrane protein 4.1. Forms of elliptocytosis not linked to Rh are due to mutations in the alpha-spectrin gene, the beta-spectrin gene, or the band 3 gene.
    EM: Electron microscopy . Or electron microscopy. Viral particles may be detectable by EM.
    Embryo: The organism from fertilization to, in humans, the beginning of the third month of pregnancy. After that point in time, it is termed a fetus.
    Embolization: A treatment that clogs small blood vessels and blocks the flow of blood, such as to a tumor.
    Embolus: A blockage or plug which is obstructing a blood vessel. Examples of emboli are a detached blood clot, a clump of bacteria, or other foreign material, such as air.
    Emergency Supplies Kit: You and your family can cope best by preparing for disaster before it strikes. One way to prepare is by assembling a Disaster Supplies Kit. Once disaster hits, you won’t have time to shop or search for supplies. But if you’ve gathered supplies in advance, your family can endure an evacuation or home confinement. For useful information, see the MedicineNet site on YOUR FAMILY DISASTER SUPPLIES KIT.
    Emesis: Vomiting.
    Emphysema: A lung condition featuring an abnormal accumulation of air in the tissue of the lung called alveoli (the lung's many tiny air sacs).
    Empiric risk: The chance that a disease will occur in a family based upon experience (past history, medical records, etc.) rather than theory.
    Empyema: Pus in the pleural space (space between the outer surface of the lung and the chest wall). Empyema typically is a result of a serious bacterial infection.
    Encephalitis: Inflammation of the brain. Encopresis: Inability to control the elimination of stool (fecal incontinence).
    Encapsulated: Confined to a specific area; the tumor remains in a compact form.
    Encopresis: Inability to control the elimination of stool (fecal incontinence).
    Endemic: Continuously present (as, for example, with malaria in some areas or illicit drugs in a neighborhood). The opposite of epidemic (a sudden outbreak).
    Endemic typhus: Murine typhus, an acute infectious disease with fever, headache, and rash, all quite similar to, but milder than, epidemic typhus, caused by a related microoganism, Rickettsia typhi (mooseri), transmitted to humans by rat fleas (Xenopsylla cheopis). The animal reservoir includes rats, mice and other rodents. Murine typhus occurs sporadically worldwide but is more prevalent in congested rat-infested urban areas. Also known as rat-flea typhus or urban typhus of Malaya.
    Endocardium: The lining of the interior surface of the heart chambers. Consists of a layer of endothelial cells and an underlying layer of connective tissue.
    Endocervical curettage: The removal of tissue from the inside of the cervix using a spoon-shaped instrument called a curette.
    Endocrinology: The study of the medical aspects of hormones and their associated diseases and conditions. (An endocrinologist is a doctor that specializes in the management of hormone conditions).
    Endogenous: Inside. For example, endogenous cholesterol is cholesterol that is made inside the body and is not in the diet.
    Endometriosis: A benign condition in which tissue that looks like endometrial tissue grows in abnormal places, most often in the abdomen. Although most women with endometriosis have no symptoms, pelvic pain during menstruation or ovulation can be a symptom of endometriosis. Endometriosis can also be suspected by a doctor during a physical examination and confirmed by surgery, usually laparoscopy. Treatment opptions include medication for pain, hormone therapy, and surgery.
    Endometritis: Inflammation of the endometrium. The endometrium is the inner layer of the womb (uterus).
    Endometrium: The inner layer of the uterus.
    Endonuclease: An enzyme that cleaves a nucleic acid (DNA oor RNA) at specific internal sites in the nucleotide base sequence.
    Endoscope: A flexible, lighted instrument used to examine organs such as the throat or esophagus.
    Endoscopy: A procedure in which the doctor looks inside the body through a lighted tube called an endoscope.
    Endoscopic Retrograde Cholangio-Pancreatography (ERCP): A diagnostic procedure to examine diseases of the liver, bile ducts and pancreas. It is uncomfortable but not painful, is performed under intravenous sedation, usually without general anesthesia, and has a low incidence of complications. ERCP provides important information unobtainable by other diagnostic means. Therapeutic measures can often be take at the time of ERCP to remove stones in the bile ducts or to relieve obstructions of the bile ducts.
    Endoscopy, upper: A procedure that enables the examiner (usually a gastroenterologist ) to examine the esophagus (swallowing tube ), stomach, and duodenum ( first portion of small bowel ) using a thin flexible tube (a "scope") that can be looked through or seen on a TV monitor. Also known as esophagogastroduodenoscopy or EGD.
    Endothelium: The layer of cells lining the closed internal spaces of the body such as the blood vessels and lymphatic vessels (that convey the lymph, a milky fluid). By contrast, the epithelium is the outside layer of cells that covers all the free, open surfaces of the body including the skin, and mucous membranes that communicate with the outside of the body.
    ENGERIX-B: A vaccine against hepatitis B (hep B) to stimulate the body’s immune system to produce antibodies against the hep B virus.
    Enophthalmos: Sunken eyeball.
    Enoxaparin: A low-molecular-weight version of heparin which acts like heparin as an anticoagulant (anti-clotting) medication. Enoxaparin is used to prevent thromboembolic complications (clots that travel from their site of origin through the blood stream to clog up another vessel). Enoxaparin is also used in the early treatment of blood clots in the lungs (pulmonary embolisms).
    E.N.T.: Ear, Nose, and Throat. An E.N.T. physician is specialist concerned with the treatment of disorders of the head and neck including particularly the ears, nose, and throat.
    Enteric: Of or relating to the small intestine.
    Enteric-coated: Coated with a material that permits transit through the stomach to the small intestine before the medication is released.
    Enteritis, Crohn’s: Crohn’s disease involving only the small intestine. Crohn’s disease is a chronic inflammatory disease of the intestine primarily affecting the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition with periods of remission and exacerbation. In the early stages, Crohn’s disease causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery.
    Enteritis, granulomatous: Crohn’s disease by another name, a chronic inflammatory disease of the intestine primarily in the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition with periods of remission and exacerbation. In the early stages, Crohn’s disease causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causinG scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs.When only the large intestine (colon) is involved, the condition is called Crohn’s colitis. When only the small intestine is involved, the condition is called Crohn’s enteritis. When only the end of the small intestine (the terminal ileum) is involved, it is termed terminal ileitis. When both the small intestine and the large intestine are involved, the condition is called Crohn’s enterocolitis (or ileocolitis). Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery. (The disease is also called regional enteritis).
    Enteritis, regional: Crohn’s disease by another name, a chronic inflammatory disease of the intestine primarily in the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition with periods of remission and exacerbation. In the early stages, Crohn’s disease causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs. When only the large intestine (colon) is involved, the condition is called Crohn’s colitis. When only the small intestine is involved, the condition is called Crohn’s enteritis. When only the end of the small intestine (the terminal ileum) is involved, it is termed terminal ileitis. When both the small intestine and the large intestine are involved, the condition is called Crohn’s enterocolitis (or ileocolitis). Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery. (The disease is also called granulomatous enteritis).
    Entero-: Combining form that means the intestine (gut). Comes from the Greek word enteron for intestine, related to the Greek enteros meaning within. What went within the intestine was within the body.
    Enterocolitis, Crohn’s: Crohn’s disease involving both the small and large intestines. Crohn’s is a chronic inflammatory disease of the intestine primarily affecting the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition with periods of remission and exacerbation. In the early stages, Crohn’s disease causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs. Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery. (The disease is also called regional enteritis and granulomatous enteritis).
    Enteropathy: Any pathology (disease) of the intestine.
    Enteropathy, gluten: A condition in which the absorption of food nutrients through the small intestine is impaired because of an immune (allergic) reaction to gluten, a protein found in wheat or related grains and many other foods. Frequent diarrhea and weight loss can be symptoms. A skin condition called dermatitis herpetiformis can be associated with gluten enteropathy. The most accurate test is a biopsy of the involved small bowel. Treatment is avoidance of gluten in the diet. Medications are used, if need be.
    Enteropathy, protein-losing: Condition in which plasma protein is lost to excess into the intestine. This can be due to diverse causes including gluten enteropathy, extensive ulceration of the intestine, intestinal lymphatic blockage, and infiltration of leukemic cells into the intestinal wall.
    Enterostomal therapist: A health care specialist trained to help patients care for and adjust to their colostomy.
    Enuresis: Bedwetting.
    Environmental tobacco smoke: Smoke that comes from the burning end of a cigarette and smoke that is exhaled by smokers. Also called ETS or second-hand smoke. Inhaling ETS is called involuntary or passive smoking.
    Enzyme: A protein that acts as a catalyst to mediate and speed a specific chemical reaction.
    Enzyme defect: A disorder resulting from a deficiency (or functional abnormality) of an enzyme. In 1902 Archibald Garrod first attributed a disease to an enzyme defect: an inborn error of metabolism. Today, newborns are routinely screened for certain enzyme defects such as PKU (phenylketonuria) and galactosemia, an error in the handling (metabolism) of the sugar galactose.
    Eosinophil: A type of white blood cell. For example, the numbers of eosinophils in blood often rise in allergy.
    Eosinophilic fasciitis (Shulman’s syndrome): A disease which leads to inflammation and thickening of the skin and fascia. (The fascia is a lining tissue under the skin that covers a surface of underlying tissues. When the fascia is inflamed, the condition is referred to as "fasciitis.") In eosinophilic fasciitis, the involved fascia is inflamed with the eosinophil white blood cells. There is progressive thickening, and often redness and warmth, and hardness of the skin surface.
    Ependymoma: A type of brain tumor.
    Epicanthal fold: A fold of skin that comes down across the inner angle of the eye. The epicanthal fold is more common in children with Down syndrome and other birth defects than normal children and so is of value in diagnosis. Although some dictionaries state that this eye fold is found in peoples of Asian origin, this is not true. The normal Asian eyefold is continuous with the lower edge of the upper eyelid and actually appears distinctly different than a true epicanthal fold.
    Epicardium: The thin surface layer of the heart. Also considered part of the pericardium, it consists of a layer of mesothelial cells and underlying stromal layer.
    Epidemic: A sudden outbreak as, for example, of cholera. The opposite of endemic (continuously present). The word epidemic came from the Greek "epidemios" meaning "among the people."
    Epidemic typhus: A severe acute disease with prolonged high fever up to 40° C (104° F), intractable headache, and a pink-to-red raised rash. The cause is a microorganism called Rickettsia prowazekii. It is found worldwide and is transmitted by lice. The lice become infected on typhus patients and transmit illness to other people. The mortality increases with age and over half of untreated persons age 50 or more die. Also called European, classic, or louse-borne typhus and jail fever.
    Epidemiologist: A person engaged in epidemiology (not confined to epidemics). Epidemiologists include people with an M.D., Ph.D., D.P.H. (Doctor of Public Health), M.P.H. (Master of Public Health), R.N., and a number of other degrees.
    Epidemiology, classical: The study of populations in order to determine the frequency and distribution of disease and measure risks.
    Epidemiology, clinical: Epidemiology focused specifically upon patients.
    Epidermis: The upper or outer layer of the two main layers of cells that make up the skin.
    Epidermoid carcinoma: A type of lung cancer in which the cells are flat and look like fish scales. Also called squamous cell carcinoma.
    Epididymis: A structure within the scrotum attached to the backside of the testis. The epididymis is a coiled segment of the spermatic ducts that serves to store, mature and transport spermatozoa between the testis and the vas (the vas deferens).
    Epididymitis: Inflammation of the epididymis.
    Epigastrium: The part of the abdominal wall above the umbilicus (belly button). The hypogastrium is the part of the abdominal wall below the umbilicus. The abdominal wall can thus be divided into upper and lower halves. Or it can be further divided into quadrants by also drawing a vertical line through the umbilicus.
    Epiglottis: The flap that covers the trachea during swallowing so that food does not enter the lungs. Not everything in medicine is perfectly logical. The name epiglottis was compounded from "epi-" and "-glottis" from the Greek "glotta" meaning "tongue" since it was once believed that the epiglottis was attached to the tongue!
    Epilepsy (seizure disorder): When nerve cells in the brain fire electrical impulses at a rate of up to four times higher than normal, this causes a sort of electrical storm in the brain, known as a seizure. A pattern of repeated seizures is referred to as epilepsy. Known causes include head injuries, brain tumors, lead poisoning, maldevelopment of the brain, genetic and infectious illnesses. But in fully half of cases, no cause can be found. Medication controls seizures for the majority of patients.
    Epinephrine: A substance produced by the medulla (inside) of the adrenal gland. The name epinephrine was coined in 1898 by the American pharmacologist and physiologic chemist (biochemist) John Jacob Abel who isolated it from the adrenal gland which is located above (epi-) the kidney ("nephros" in Greek). (Abel also crystallized insulin). Technically speaking, epinephrine is a sympathomimetic catcholamine. It causes quickening of the heart beat, strengthens the force of the heart’s contraction, opens up the airways (bronchioles) in the lungs and has numerous other effects. The secretion of epinephrine by the adrenal is part of the fight-or-flight reaction. Adrenaline is a synonym of epinephrine and is the official name in the British Pharmacopoeia.
    Epiphysis: The growth area of a bone near the end.
    Episiotomy: Surgical procedure for widening the outlet of the birth canal to facilitate delivery of the baby and avoid a jagged rip of the perineum (the area between the anus and the vulva, the labial opening to the vagina).
    Epispadias: Congenital (at birth) malformation in which the opening of the urethra (from whence comes the urinary stream) is on the dorsum (topside) of the penis. Hypospadias is the corresponding malformation in which the opening of the urethra is on the ventral surface (underside) of the penis.
    Epistaxis: Medical term for nosebleed. The nose is a part of the body that is very rich in blood vessels (vascular) and is situated in a vulnerable position on the face. As a result, any trauma to the face can cause bleeding which may be profuse. Nosebleeds can occur spontaneously when the nasal membranes dry out, crust, and crack, as is common in dry climates, or during the winter months when the air is dry and warm from household heaters. People are more susceptible if they are taking medications which prevent normal blood clotting (coumadin, warfarin, aspirin, or any anti-inflammatory medication). Other predisposing factors include infection, trauma, allergic and non-allergic rhinitis, hypertension, alcohol abuse, and inherited bleeding problems.
    Epistaxis, treatment of: To stop epistaxis (a nosebleed), you should: 1. Pinch all the soft parts of the nose together between your thumb and index finger. 2. Press firmly toward the face - compressing the pinched parts of the nose against the bones of the face. 3. Hold the nose for at least 5 minutes (timed by the clock). Repeat as necessary until the nose has stopped bleeding. 4. Sit quietly, keeping the head higher than the level of the heart; that is, sit up or lie with the head elevated. Do not lay flat or put your head between your legs. 5. Apply ice (crushed in a plastic bag or washcloth) to nose and cheeks.
    Epithelial carcinoma: Cancer that begins in the cells that line an organ.
    Epithelium: The outside layer of cells that covers all the free, open surfaces of the body including the skin, and mucous membranes that communicate with the outside of the body. By contrast the endothelium is the layer of cells lining the closed internal spaces of the body such as the blood vessels and lymphatic vessels (that convey the lymph, a milky fluid).
    Eponym: Something named after someone. For example, a condition called Shiel’s syndrome might be named after someone named Shiel who discovered it or described and clearly delineated it.
    Epstein-Barr Virus: A virus that can cause infectious mononucleosis ("mono").
    ERCP (endoscopic retrograde cholangiopancreatogram): A diagnostic procedure to examine diseases of the liver, bile ducts and pancreas. It is uncomfortable but not painful, is performed under intravenous sedation, usually without general anesthesia, and has a low incidence of complications. ERCP provides important information unobtainable by other diagnostic means. Therapeutic measures can often be take at the time of ERCP to remove stones in the bile ducts or to relieve obstructions of the bile ducts.
    ERCP (Endoscopic Retrograde Cholangio-Pancreatography): A diagnostic procedure to examine diseases of the liver, bile ducts and pancreas. It is uncomfortable but not painful, is performed under intravenous sedation, usually without general anesthesia, and has a low incidence of complications. ERCP provides important information unobtainable by other diagnostic means. Therapeutic measures can often be take at the time of ERCP to remove stones in the bile ducts or to relieve obstructions of the bile ducts.
    Erectile dysfunction: A consistent inability to sustain an erection sufficient for sexual intercourse. Also commonaly known as "impotence." Medically, the term "erectile dysfunction" is used to differentiate impotence from other problems that interfere with sexual intercourse (such as lack of sexual desire and problems with ejaculation and orgasm). Impotence usually has a physical cause, such as disease, injury, drug side-effects, or a disorder that impairs blood flow in the penis. Impotence is treatable in all age groups.
    Erection, penile: When the penis fills with blood and is rigid. The penis contains two chambers, called the corpora cavernosa, which run the length of the organ, are filled with spongy tissue, and surrounded by a membrane, called the tunica albuginea. The spongy tissue contains smooth muscles, fibrous tissues, spaces, veins, and arteries. The urethra, which is the channel for urine and ejaculate, runs along the underside of the corpora cavernosa. Erection begins with sensory and mental stimulation. Impulses from the brain and local nerves cause the muscles of the corpora cavernosa to relax, allowing blood to flow in and fill the open spaces. The blood creates pressure in the corpora cavernosa, making the penis expand. The tunica albuginea helps to trap the blood in the corpora cavernosa, thereby sustaining erection. Erection is reversed when muscles in the penis contract, stopping the inflow of blood and opening outflow channels.
    Erythema: A redness of the skin resulting from inflammation, for example, as caused by sunburn.
    Erythema chronicum migrans: The classic initial rash of Lyme disease. In the early phase of the illness, within hours to weeks of the tick bite, the local skin develops an expanding ring of unraised redness. There may be an outer ring of brighter redness and a central area of clearing. For more information, see LYME DISEASE.
    Erythema infectiosum: A Latin name for fifth disease—because in the pre-vaccination era, it was frequently the "fifth disease" that a child would develop—caused by a virus known as parvovirus B 19. Symptoms include low-grade fever, fatigue, a "slapped cheeks rash," and a rash over the whole body. While the illness is not serious in children, 80% of adults have joint aches and pains (arthritis) which may become long-term with stiffness in the morning, redness and swelling of the same joints on both sides of the body (a "symmetrical" arthritis), most commonly involving the knees, fingers, and wrists. Pregnant women (who have not previously had the illness) should avoid contact with patients who have fifth disease. The fifth disease virus can infect the fetus prior to birth. And, while no birth defects have been reported as a result of fifth disease, it can cause the death of the unborn fetus. The risk of fetal death is 5-10% if the mother becomes infected.
    Erythrocytes: Cells that carry oxygen to all parts of the body. Also called red blood cells (RBCs).
    Erythrocyte membrane protein band 4.1 (EPB41): See Elliptocytosis.
    Erythroleukemia: Leukemia that develops in erythrocytes. In this rare disease, the body produces large numbers of abnormal red blood cells.
    Erythroplakia: A reddened patch with a velvety surface found in the mouth.
    Eschar: The scab formed when a wound or skin is sealed by the heat of cautery or burning. Also the dark crusted ulcer (tache noire) at the site of the chigger (mite larva) bite in scrub typhus.
    Esophageal: Related to the esophagus.
    Esophageal cancer: Cancer of the esophagus (the swallowing tube that passes from the throat to the stomach). The risk of cancer of the esophagus is increased by long-term irritation of the esophagus such as with smoking, heavy alcohol intake, and Barrett’s esophagitis. Cancer of the esophagus can cause difficulty and pain with swallowing solid food. Diagnosis of esophageal cancer can be made by barium x-ray of the esophagus, and confirmed by endoscopy with biopsy of the cancer tissue.
    Esophageal reflux: A condition wherein stomach contents regurgitate or back up (reflux) into the esophagus (a long cylindrical tube that transports food from the mouth to the stomach). The food in the stomach is partially digested by stomach acid and enzymes. Normally, the partially digested acid content in the stomach is delivered by the stomach muscle into the small intestine for further digestion. In esophageal reflux, stomach acid content refluxes backwards up into the esophagus, occasionally reaching the breathing passages, causing inflammation and damage to the esophagus, as well as to the lung and larynx (the voice box). The process is medically termed gastroesophageal reflux disease (GERD). 10% of patients with GERD develop a Barrett’s esophagus which can increase the risk of cancer of the esophagus.
    Esophageal speech: Speech produced with air trapped in the esophagus and forced out again.
    Esophageal stricture, acute: A narrowing or closure of the normal opening of the swallowing tube leading to the stomach, usually caused by scarring from acid irritation. Acute, complete obstruction of the esophagus occurs when food (usually meat) is lodged in the esophageal stricture. Patients experience chest pain, and are unable to swallow saliva. Attempts to relieve the obstruction by inducing vomiting at home are usually unsuccessful. Patients with complete esophageal obstruction can breathe, and are not at any risk of suffocation. Endoscopy is usually employed to retrieve the meat and relieve the obstruction.
    Esophageal stricture, chronic: A longstanding narrowing or closure of the normal opening of the swallowing tube leading to the stomach, usually caused by scarring by acid irritation. Narrowing of the esophagus. A common complication of chronic gastroesophageal reflux disease (GERD). Severa procedures are available for stretching (dilating) the strictures without having to resort to surgery. One of the procedures involves placing a deflated balloon across the stricture at the time of endoscopy. The balloon is then inflated, thereby opening the narrowingcaused by the stricture. Another method involves inserting tapered dilators of different sizes through the mouth into the esophagus to dilate the stricture.
    Esophageal ulcer: A hole in the lining of the esophagus corroded by the acidic digestive juices secreted by the stomach cells. Ulcer formation is related to H. pyloridus bacteria in the stomach, anti-inflammatory medications, and smoking cigarettes. Ulcer pain may not correlate with the presence or severity of ulceration. Diagnosis is made with barium x-ray or endoscopy. Complications of ulcers include bleeding and perforation. Treatment involves antibiotics to eradicate H. pyloridus, eliminating risk factors, and preventing complications.
    Esophagectomy: An operation to remove a portion of the esophagus.
    Esophagitis: Inflammation of the esophagus. The esophagus is that soft tube-like portion of the digestive tract connecting the pharynx with the stomach.
    Esophagogastroduodenoscopy: Also known as EGD (for EsophagoGastroDuodenoscopy) or as upper endoscopy. A procedure that enables the examiner ( usually a gastroenterologist) to examine the esophagus (swallowing tube ), stomach, and duodenum (first portion of small bowel ) using a thin flexible tube (a "scope") that can be looked through or seen on a TV monitor. (A great crossword puzzle/trivia term!)
    Esophagoscopy: Examination of the esophagus using a thin, lighted instrument.
    Esophagram: A series of x-rays of the esophagus. The x-ray pictures are taken after the patient drinks a solution that coats and outlines the walls of the esophagus. Also called a barium swallow.
    Esophagus: The esophagus is that soft tube-like portion of the digestive tract connecting the pharynx with the stomach. It has a muscular wall composed of "smooth muscle." It is commonly referred to as the "gullet."
    Escherichia coli: Full term for E. coli, the colon bacillus.
    EST: Expressed sequence tag. A sequence tagged site (STS) derived from cDNA (complementary DNA). An STS is a short (200 to 500 base pairs) DNA sequence that has a single occurrence in the human genome and whose location and base sequence are known. Detectable by polymerase chain reaction, STSs are useful for localizing and orienting the mapping and sequence data reported from many different laboratories and serve as landmarks on the developing physical map of the human genome.
    Estrogen: Estrogen is a female hormone produced by the ovaries. Estrogen deficiency can lead to osteoporosis.
    Estrogen, designer: An engineered drug that possesses some, but not all, of the actions of estrogen. Designer estrogens are selective estrogen-receptor modulators (SERMs). For example, raloxifene (trade name Evista) is classified as a SERM because it prevents bone loss (like estrogen) and lowers serum cholesterol (like estrogen) but (unlike estrogen) does not stimulate the endometrial lining of the uterus.
    Esotropia: Cross-eyed or, in medical terms, convergent or internal strabismus.
    Essential: As in essential hypertension. A hallowed term meaning "We don't know the cause." Synonymous with idiopathic.
    Eugenics: Literally, meaning normal genes, eugenics aims to improve the genetic constitution of the human species by selective breed

  • F: The symbol for the coefficient of inbreeding, a way of gauging how close two people are genetically to one another. For more, see: Coefficient of inbreeding.
    Facelift surgery: Procedure to make the face appear younger. Recovery time is usually one week. Results last approximately ten years. Additional procedures to supplement the facelift—including necklift, blepharoplasty (eyelid surgery), liposuction, autologous fat injection, removal of buccal (cheek) fat pad, forehead lift, browlift, chemical or laser peel, and malar (cheek), submalar or chin implants—may be necessary to achieve the desired results.
    Facelift surgery risks: Although infrequent, the risks and complications of facelift surgery include: bleeding, hematoma, bruising; infection; neurological dysfunction (loss of muscle function or sensation), which is usually temporary; widened or thickened scar; loss of hair (around the incision site), asymmetry (unevenness between two sides); and skin necrosis (loss of skin from tissue death).
    Facies: A direct borrowing from the Latin, facies means face.
    Factor, rheumatoid: Rheumatoid factor is an antibody that is measurable in the blood. It is commonly used as a blood test for the diagnosis of rheumatoid arthritis. Rheumatoid factor is present in about 80% of adults (but a much lower proportion of children) with rheumatoid arthritis. It is also present in patients with other connective tissue diseases (such as systemic lupus erythematosus) and in some with infectious diseases (such as infectious hepatitis).
    Factor VIII: A coagulation (clotting) factor. Classic hemophilia (hemophilia A) is due to a congenital deficiency in the amount (or activity) of factor VIII. Factor VIII is also known as antihemophiliac factor (AHF) or antihemophiliac globulin (AHG). The gene for factor VIII (that for classic hemophilia) is on the X chromosome so females can be silent carriers without symptoms and males can be hemophiliacs.
    FAE (fetal alcohol effects): A softer diagnosis than fetal alcohol syndrome (FAS). The diagnosis of possible FAE is considered when: 1. The person has some signs of FAS; 2. The person does not meet all of the necessary criteria for FAS; and 3. There is a history of alcohol exposure before birth.
    Falciparum malaria: The most dangerous type of malaria. Persons carrying the sickle cell gene have some protection against malaria. Persons with a gene for hemoglobin C (another abnormal hemoglobin like sickle hemoglobin), thalassemia trait or deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD) are thought also to have partial protection against malaria.
    Fallopian tubes: The fallopian tubes normally transport the egg of the female from the egg sac, or ovary, to the womb, or uterus. Normal tubes have small hair like projections on the lining cells called cilia. These cilia are important to movement of the egg through the fallopian tube and into the uterus. If the tubal cilia are damaged by infection, the egg may not get 'pushed along' normally and can settle in the tube. Likewise, if infection causes partial blockage of the tube with scar tissue, this can also act to prevent the egg from getting to the uterus. Any process that narrows the tube and thus decrease the caliber of the passage way can increase the chance of an ectopic pregnancy. Examples of these would be endometriosis, tumors, or scar tissue in the pelvis (pelvic adhesions) that cause twisting or chinking of the tube.
    Familial: A condition that is more common in certain families than in the general population.
    Familial adenomatous polyposis (FAP): Genetic disease with numerous precancerous polyps in the colon and rectum. Also called familial polyposis.
    Familial cancer: Cancer or a predisposition (tendency) to it that runs in families.
    Familial hypercholesterolemia: This is the most common inherited type of hyperlipidemia (high lipid levels in blood). It is recognizable in childhood. Familial hypercholesterolemia is due to genetic defects in the receptor (target) for LDL (low density lipoprotein). Familial hypercholesterolemia predisposes to premature arteriosclerosis including coronary artery disease with heart attacks at an unusually young age.
    Familial Mediterranean Fever (FMF): A inherited disorder of unknown cause featuring short recurring bouts of fever together with pain in the joints, chest or abdomen. Between attacks, the patient seems healthy (when FMF is more difficult to diagnose). The gene for FMF (autosomal recessive, on chromosome 16) was reportedly identified in August, 1997. FMF is found in persons of Mediterranean ethnic background.
    Familial mental retardation 1: See FMR1.
    Familial mental retardation protein: See FMRP.
    Familial polyposis: An inherited condition in which several hundred polyps develop in the colon and rectum.
    FAS (fetal alcohol syndrome): The sum total of the damage done to the child before birth as a result of the mother drinking alcohol during pregnancy. FAS always involves brain damage, impaired growth, and head and face abnormalities. No amount of alcohol has been proven safe during pregnancy. Women who are or may become pregnant are advised to avoid alcohol.
    FAS (fetal alcohol syndrome) diagnosis: To establish the diagnosis of FAS, the following signs must be present: 1. Small size and weight before and after birth (pre- and postnatal growth retardation); 2. Brain involvement with evidence for delay in development, intellectual impairment, or neurologic abnormalities; and 3. Specific appearance of the head and face with at least 2 of the following groups of signs: a. Small head size (microcephaly); b. Small eyes (microphthalmia) and/or short eye openings (palpebral fissures); c. Underdevelopment of the upper lip, indistinct groove between the lip and nose (the philtrum), and flattened cheekbones.
    Fascia: The fascia is a lining tissue under the skin that covers a surface of underlying tissues. Fascia also encloses muscles. Inflammation of the fascia is referred to as fasciitis.
    Fasciitis: Inflammation of the fascia (a lining tissue under the skin that covers a surface of underlying tissues).
    Fasciitis, eosinophilic (Shulman’s syndrome): A disease which leads to inflammation and thickening of the skin and fascia. (The fascia is a lining tissue under the skin that covers a surface of underlying tissues. When the fascia is inflamed, the condition is referred to as "fasciitis.") In eosinophilic fasciitis, the involved fascia is inflamed with the eosinophil white blood cells. There is progressive thickening, and often redness and warmth, and hardness of the skin surface.
    Fasciitis, plantar: Inflammation of the plantar fascia (fasciitis), the "bowstring-like" tissue stretching underneath the sole which attaches at the heel.
    Fat: Comes from the Old English faett meaning to cram or adorn. A slang term for obese or adipose. In chemistry, fats are compounds formed from chemicals called fatty acids. These fats compose a greasy, solid material found in animal tissues and in some plants. Fats are the major component of flabby material of our bodies, commonly known as blubber.
    Fetal circulation: The blood circulation in the fetus before birth. Before birth, the blood from the heart headed for the lungs in the aptly named pulmonary artery is shunted away from the lungs and returned to the greatest of arteries, the aorta. This arterial shunting occurs through a short vessel called the ductus arteriosus. When the shunt is open, it is said to be patent (pronounced pá tent). The ductus arteriosus usually tourniquets itself off at or shortly after birth. After closure of the ductus, blood is permitted from that time on to course freely to the lungs. Sometimes, however, the patent ductus arteriosus (PDA) persists and simply will not close by itself. Surgery is then done to ligate (tie off) the ductus PDA ligation is a closed-heart operation. Historically, it was one of the earliest surgical procedures performed in children with cardiovascular disease.
    Fauces: The throat. The word fauces is the plural of the Latin faux meaning a small passage.
    Fava bean: The broad bean to which many people react adversely with an acute hemolytic anemia with sudden breakup of red blood cells (see Favism). Fava beans look like large tan lima beans. They are popular in Mediterranean and Middle Eastern cuisines, are eaten raw when very young, cooked in soups and many other dishes, and made into fava brittle (like peanut brittle) as candy. The botanical name for fava is Vicia fava. Fava is Italian for bean and refers specifically to the broad bean. Fava beans are the main commercial source of the drug L-DOPA.
    Favism: A condition characterized by hemolytic anemia (breakup of red blood cells) after eating fava beans (Vicia fava) or being exposed to the pollen of the fava plant. This dangerous reaction occurs exclusively in people with a deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), an X-linked genetic trait. However, not all G6PD-deficient families appear at risk for favism, indicating the additional need for a single autosomal (not X-linked) gene to create the susceptibility to favism of G6PD-deficient persons. The active hemolytic principle in fava beans is > likely DOPA-quinone. Differences in susceptibility to favism may be related to differences in the enzymatic system that converts L-DOPA to DOPA-quinone.
    Febrile: Feverish.
    Fecal occult blood test: A test to check for hidden blood in stool. (Fecal refers to stool. Occult means hidden.)
    Feces: The proper medical term for the "excrement discharged from the intestines." The word "feces" (or its English version "faeces") in Shakespeare in this context until the 17th century "feces" merely meant the "dregs or sediment" of wine or some other fermented product.
    Fecund: Fruitful. Just as a writer is prolific, a woman may be fecund, able to reproduce plentifully.
    Fecundity: The ability to have children, usually lots of them with ease.
    Feedback: Many biologic processes are controlled by feedback, just as the temperature in a home from a furnace is regulated by a thermostat.
    Feeding, breast: The ability of the breast to produce milk diminishes soon after childbirth without the stimulation of breastfeeding. Immunity factors in breast milk can help the baby to fight off infections. Breast milk contains vitamins, minerals, and enzymes which aid the baby’s digestion. Breast and formula feeding can be used together.
    Feet: As a measure of length, the plural of foot. See Foot.
    Femoral: Having to do with the femur.
    Femur: The femur is a large bone of the lower extremity that extends from the hip to the knee.
    Female: The traditional definition of female was "an individual of the sex that bears young" or "that produces ova or eggs". However, things are not so simple today. Female can be defined by physical appearance, by chromosome constitution (see Female chromosome complement), or by gender identification. Female chromosome complement: The large majority of females have a 46, XX chromosome complement (46 chromosomes including two X chromosomes). A minority of females have other chromosome constitutions such as 45,X (45 chromosomes including only one X chromosome) and 47,XXX (47 chromosomes including three X chromosomes).
    Fenstration: Literally, the making of a window -- fenestra in Latin (and fenetre in French) is a window -- fenestration refers to the creation of a new opening.
    Ferritin: A blood protein that serves as an indicator of the amount of iron stored in the body.
    Fetal alcohol effects (FAE): A softer diagnosis than fetal alcohol syndrome (FAS). The diagnosis of possible FAE is considered when: 1. The person has some signs of FAS; 2. The person does not meet all of the necessary criteria for FAS; and 3. There is a history of alcohol exposure before birth.
    Fetal alcohol syndrome (FAS): The sum total of the damage done to the child before birth as a result of the mother drinking alcohol during pregnancy. FAS always involves brain damage, impaired growth, and head and face abnormalities. No amount of alcohol has been proven safe during pregnancy. Women who are or may become pregnant are advised to avoid alcohol.
    Fetal alcohol syndrome (FAS) diagnosis: To establish the diagnosis of FAS, the following signs must be present: 1. Small size and weight before and after birth (pre- and postnatal growth retardation); 2. Brain involvement with evidence for delay in development, intellectual impairment, or neurologic abnormalities; and 3. Specific appearance of the head and face with at least 2 of the following groups of signs: a. Small head size (microcephaly); b. Small eyes (microphthalmia) and/or short eye openings (palpebral fissures); c. Underdevelopment of the upper lip, indistinct groove between the lip and nose (the philtrum), and flattened cheekbones.
    Fertile: Able to conceive and bear offspring.
    Fertility: The ability to have children.
    Fertilization: Fertilization is the process of combining the male gamete, or "sperm," with the female gamete, or "ovum." The product of this combination is a cell called a zygote.
    Fetal distress: Compromise of the fetus during the antepartum period (before labor) or intrapartum period (birth process).
    Fetal mortality rate: The ratio of fetal deaths divided by the sum of the births (the live births + the fetal deaths) in that year. In the United States, the fetal mortality rate plummeted from 19.2 per 1,000 births in 1950 to 9.2 per 1,000 births in 1980.
    Fetoprotein, Alpha-: A plasma protein, alpha-fetoprotein (AFP) is normally produced by the fetus. The level of AFP in the blood serum of pregnant women provides a screening test for open neural tube defects (anencephaly and spina bifida) and for Down syndrome (and other chromosome abnormalities). The maternal serum AFP (MSAFP) tends to be high with open neural tube defects and low with Down syndrome. AFP is also paradoxically produced by liver tumors (hepatomas) and germ cell tumors (teratocarcinoma and embryonal cell carcinomas) and so can be used to help detect and monitor the treatment of these tumors.
    Fetoscope: There are two types of fetoscopes: one is a fiberoptic scope for looking directly at the fetus within the uterus; the other is a stethescope designed for listening to the fetal heart beat.
    Fetoscopy: A technique for looking directly at the fetus within the uterus (using a fetoscope).
    Fetus: The postembryonic stage before birth. In humans, the embyronic stage runs from conception to the beginning of the third month of pregnancy and the fetal stage runs from the start of the third month of preganancy until birth.
    Fever: Although a fever technically is any body temperature above the normal of 98.6 degrees F. (37 degrees C.), in practice a person is usually not considered to have a significant fever until the temperature is above 100.4 degrees F (38 degrees C.). The temperature is measured with a thermometer.
    Fever blisters: Common with a wide range of infectious diseases.
    Fever, five-day: See Fever, trench.
    Fever, Mediterranean: See Familial Mediterranean Fever.
    Fever, Meuse: Named for the Meuse River area, one of the great battlegounds of World War I. See Fever, trench.
    Fever, Q: An acute (abrupt-onset), self-limited febrile illness first reported in 1935 in Queensland, Australia. The Q is said not to be for Queensland, but for Query since the cause of the disease was long a query (question mark). It is now known to be due to Coxiella burnetti, a rickettsia (a peculiar group of bacteria). Aside from sudden onset of fever, there is headache, malaise, and pneumonia (interstitial pneumonitis) but no rash.
    Fever, quintan: Quintan means recurring every 5 days. See Fever, trench.
    Fever, Rocky Mountain spotted (RMSF): An acute febrile (feverish) disease initially recognized in the Rocky Mountain states, caused by Rickettsia rickettsii transmitted by hard-shelled (ixodid) ticks. Occurs only in the Western Hemisphere. Anyone frequenting tick-infested areas is at risk for RMSF. Onset of symptoms is abrupt with headache, high fever, chills, muscle pain. and then a rash .The rickettsiae grow within damaged cells lining blood vessels which may become blocked by clots. Blood vessel inflammation (vasculitis) is widespread Early recognition of RMSF and prompt antibiotic treatment is important in reducing mortality. Also called spotted fever, tick fever, and tick typhus.
    Fever, shin bone: See Fever, trench.
    Fever, splenic: Known also as anthrax, splenic fever is a serious bacterial infection. It is not primarily a human disease but rather an infection of animals. Cattle, sheep, horses, mules, and some wild animals are highly susceptible. Humans (and swine) are generally resistant to anthrax. Anthrax can take different forms. With the lung form of the disease. People inhale the anthrax spores and, if untreated, are likely to die. An intestinal form is caused by eating meat contaminated with anthrax. But most human anthrax comes from skin contact with animal products. Cutaneous (skin) anthrax was once well known among people who handled infected animals, like farmers, woolsorters, tanners, brushmakers and carpetmakers in the days when the brushes and carpets were animal products. The hallmark of skin anthrax is a carbuncle, a cluster of boils, that ulcerates in an ugly way. Typically this lesion has a hard black center surrounded by bright red inflammation. This accounts for its name, "anthrax", the Greek word for "coal."
    Fever, spotted: See Fever, Rocky Mountain spotted.
    Fever, tick: See Fever, Rocky Mountain spotted.
    Fever, trench: A louse-borne disease first recognized in the trenches of World War I, again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Also called Wolhynia fever, shin bone fever, quintan fever, five-day fever, Meuse fever, His’ disease, His-Werner disease, Werner-His disease.
    Fever, Wolhynia: See Fever, trench.
    Fiber: The parts of fruits and vegetables that cannot be digested. Also called bulk or roughage.
    Fiber and bowel disorders: High fiber diets help delay the progression of diverticulosis and, at least, reduce the bouts of diverticulitis. In many cases, it helps reduce the symptoms of the Irritable Bowel Syndrome (IBS) (also called spastic colitis, mucus colitis, and nervous colon syndrome.) It is generally accepted that a diet high in fiber is protective, or at least reduces the incidence, of colon polyps and colon cancer.
    Fiber and cholesterol: Soluble fiber substances are effective in helping reduce the blood cholesterol. This is especially true with oat bran, fruits, psyllium and legumes. High soluble-fiber diets may lower cholesterol and low-density lipoproteins ( the ‘bad’ lipoproteins ) by 8% to 15%.
    Fiber and constipation: Insoluble fiber retains water in the colon, resulting in a softer and larger stool. It is used effectively in treating constipation resulting from poor dietary habits. Bran is particularly rich in insoluble fiber.
    Fiber and diabetes: Soluble fibers (oat bran, apples, citrus, pears, peas/beans, psyllium, etc.) slow down the digestion of carbohydrates (sugars), which results in better glucose metabolism. Some patients with the adult-onset diabetes may actually be successfully treated with a high-fiber diet alone, and those on insulin, can often reduce their insulin requirements by adhering to a high-fiber diet.
    Fiber, soluble and insoluble: Fiber is classified as soluble (oat bran, apples, citrus, pears, peas/beans, psyllium, etc.) and insoluble (wheat bran, cabbage, peas/beans, rne through bacterial action).
    Fibril: The diminuitive of fiber. A small fiber, a fine thread.

  • G: Guanine, one member of the base pair G-C (guanine-cytosine) in DNA.
    Gait: Manner of walking.
    Galactose: Sugar found in milk.
    Galactosemia: Inherited disorder due to defective metabolism (processing) of the sugar galactose. Galactosemia is one of the diseases in many newborn genetic screening panels. The disease (which can be fatal, if undetected) is treated by avoiding galactose in the diet.
    Gallbladder: A pear-shaped organ that stores bile. It is located below the liver.
    Gallstones: Stones in the gallbladder or in the duct leading from the gallbladder to the intestine. There are many types of gallstones.
    Gallstones and ERCP (Endoscopic Retrograde Cholangio-Pancreatography): A diagnostic procedure to examine diseases of the bile ducts, liver and pancreas. It is uncomfortable but not painful, is performed under intravenous sedation, usually without general anesthesia, and has a low incidence of complications. ERCP provides important diagnostic information unobtainable by other means. Therapeutic measures can often be take at the time of ERCP to remove stones in the bile ducts or to relieve obstructions of the bile ducts, so that traditional open surgeries can be avoided. ERCP is increasingly accepted as the diagnostic and therapeutic procedure of choice in identifying and removing gallstones in the bile ducts.
    Gallop rhythm: Heart rhythm like the gallop of a horse.
    Gamete: The sperm or egg. In humans, the gametes normally have 23 chromosomes.
    Ganglion: The 2nd century Roman physician Galen first used the word ganglion to denote a nerve complex. Ganglion currently refers to an aggregation of nerve cell bodies. Another use of the word ganglion is for a tendon cyst, commonly near the wrist.
    Gangrene: Gangrene is the state of death of tissue due to loss of adequate blood supply.
    Gargoylism: From the French gargouille (waterspout), the word conveys the often-grotesque image of the medieval cathedral gargoyle. The term gargoylism was once applied to a condition today called Hurler syndrome.
    Gas, intestinal: The complaint referred to as "intestinal gas" is a common one and the discomfort can be quite significant. Everyone has gas and eliminates it by burping or passing it through the rectum. In many instances people think they have too much gas when in reality they have normal amounts. Most people produce 1 to 3 pints of intestinal gas in 24 hours and pass gas an average of 14 times a day. It is made up primarily of odorless vapors such as carbon dioxide, oxygen, nitrogen, hydrogen, and in some families, methane. The unpleasant odor is due to bacteria in the large intestine that release small amounts of gases containing sulfur.
    Gastrectomy: Surgery to remove part of all of the stomach.
    Gastric: Having to do with the stomach.
    Gastric atrophy: A condition in which the stomach muscles shrink and become weak. It results in a lack of digestive juices. Gastritis: Inflammation of the stomach.
    Gastric cancer: Cancer of the stomach, the major organ that holds food for digestion. Stomach cancer (gastric cancer) can develop in any part of the stomach and spread to other organs. Stomach ulcers do not appear to increase a person’s risk of developing stomach cancer. Symptoms of stomach cancer are often vague, such as loss of appetite and weight. The cancer is diagnosed with a biopsy of stomach tissue during a procedure. called an endoscopy.
    Gastric ulcer: A hole in the lining of the stomach corroded by the acidic digestive juices which are secreted by the stomach cells. Ulcer formation is related to H. pyloridus bacteria in the stomach, anti-inflammatory medications, and smoking cigarettes. Ulcer pain may not correlate with the presence or severity of ulceration. Diagnosis is made with barium x-ray or with the use of a viewing tube slipped through the throat to the stomach (endoscopy).
    Gastritis: Inflammation of the stomach.
    Gastroenteritis: Inflammation of the stomach and the intestines. Can cause nausea and vomiting and/or diarrhea. Gastroenteritis has numerous causes: including infectious organisms (viruses, bacteria, etc.), food poisoning, and stress.
    Gastroenterologist: A doctor who specializes in diagnosing and treating diseases of the digestive system.
    Gastroesophageal reflux: The return of stomach contents back up into the esophagus This frequently causes heartburn because of irritation of the esophagus by stomach acid. Gastroesophageal reflux disease (GERD) can lead to scarring and stricture of the esophagus, requiring stretching (dilating) of the esophagus. 10% of patients with GERD develop Barrett’s esophagus which increases the risk of cancer of the esophagus. 80% of patients with GERD also have a hiatal hernia.
    Gastrointestinal (GI): Adjective encompassing the stomach and intestines.
    Gastrostomy: A surgical opening into the stomach. This opening may be used for feeding usually via a feeding tube called a gastrostomy tube.
    Gastroscope: A flexible, lighted instrument that is put through the mouth and esophagus to view the stomach. Tissue from the stomach can be removed through the gastroscope.
    Gaucher’s disease, type 1: A progressive genetic disease caused by a defect in an enzyme. The enzyme, called glucocerebrosidase, is needed to break down the chemical glucocerebroside. The enzyme defect in persons with Gaucher’s disease (GD) leads to the accumulation of glucocerebroside in the spleen, liver, and lymph nodes. The most common early sign is enlargement of the spleen (located in the upper left abdomen). Other signs include low red blood cell counts (anemia), a decrease in blood clotting cells (platelets), increased pigmentation of the skin, and a yellow fatty spot on the white of the eye (a pinguecula). Severe bone involvement can lead to pain and collapse of the bone of the hips, shoulders, and spine. The GD gene is on chromosome 1. The disease is a recessive trait. Both parents carry a GD gene and transmit it for their child with the disease. The parents’ risk of a child with the disease is 1 in 4 with each pregnancy. This type of Gaucher’s disease (noncerebral juvenile Gaucher’s disease) is most common in Ashkenazi Jews (of European origin) and is the most common genetic disease among Jews in the United States.
    GD: Gaucher’s disease.
    Gene: A gene can be defined in various ways. In classical genetics, a gene is a unit of inheritance. In molecular genetics, a gene is a sequence of chromosomal DNA required to make a functional product. Humans have 50-100,000 genes.
    Gene deletion: The total loss (or absence) of a gene. Gene deletion plays a role in birth defects and in the development of cancer.
    Gene duplication: An extra copy of a gene. Gene duplication is a key mechanism in evolution. Once a gene is duplicated, the identical genes can undergo changes and diverge to create two different genes.
    Gene, evolutionarily conserved: A gene that has remained essentially unchanged throughout evolution. Conservation of a gene indicates that it is unique and essential. There is not an extra copy of that gene with which evolution can tinker. And changes in the gene are likely to be lethal.
    Gene expression: A gene speaks. When a gene is expressed, the information encoded in the gene is translated into protein or RNA structures present and operating in the cell. Expressed genes include genes that are transcribed into messenger RNA (mRNA) and then translated into protein as well as those genes that are transcribed into RNA (such transfer and ribosomal RNAs) but not translated into protein.
    Gene family: A group of genes related in structure (and often in function). The genes in a family are descended from an ancestral gene. For example, the hemoglobin genes (of critical importance to red blood cells) belong to one gene family created by gene duplication and divergence.
    Gene markers: Detectable genetic traits or distinctive segments of DNA that serve as landmarks for a target gene. Markers are on the same chromosome as the target gene. They must be near enough to the target gene to be genetically linked to it: to be inherited usually together with that gene, and so serve as signposts to it.
    Gene mapping: Charting the relative positions of genes on a DNA molecule or chromosome and the distance, in linkage units or physical units, between them.
    General paresis: A part of late ("tertiary") syphilis a decade or more after the initial infection, due to chronic inflammation of the covering and substance of the brain (meningoencephalitis) which results in progressive dementia and generalized paralysis.
    Gene product: The RNA or protein that results from the expression of a gene. The amount of gene product is a measure of the degree of gene activity.
    Gene testing: Testing a sample of blood (or another fluid or tissue) for evidence of a gene. The evidence can be biochemical, chromosomal, or genetic. The aim is to learn whether a gene for a disease is present or absent.
    Gene therapy: The treatment of disease by replacing, altering, or supplementing a gene that is absent or abnormal and is responsible for the disease. In studies of gene therapy for cancer, researchers are trying to bolster the body's natural capacity to combat cancer and make the tumor more sensitive to other kinds of therapy. Gene therapy, still in its early stages, holds great promise for the treatment of many diseases.
    Genetic: Having to do with genes, structures found in every cell of the body. Each gene contains information that directs the activities of cells and controls the way an individual develops.
    Genetic code: The correspondence of the base triplets (trios composed of A.T.G., or C.) in DNA with the amino acids. The discovery of the genetic code clearly ranks as one of the premiere events of what has been called the Golden Age of Biology (and Medicine).
    Genetic screening: Testing a population to identify individuals at risk for a genetic disease or for transmitting it. Newborns may be screened for PKU (phenylketonuria), Jews for the gene for Tay-Sachs disease, Blacks for the sickle cell gene, etc.
    Genital: Pertaining to the external and internal organs of reproduction. (Not to be confused with genetic.)
    Genital herpes: A viral infection transmitted through intimate contact with the moist mucous linings of the genitals. This contact can involve the mouth, the vagina or the genital skin. The herpes simplex type 2 virus enters the mucous membranes through microscopic tears. Once inside, the virus travels to nerve the roots near the spinal cord and settles there permanently. When an infected person has a herpes outbreak, the virus travels down the nerve fibers to the site of the original infection and when it reaches the skin, the classic redness and blisters occur. The outbreak of herpes is closely related to the functioning of the immune system. Women who have suppressed immune systems, either through stress, disease, or medications, have more frequent and longer-lasting outbreaks. Commonly just called "herpes."
    Genital warts: Warts confined primarily to the moist skin of the genitals due to viruses belonging to the family of human papilloma viruses (HPVs) transmitted through sexual contact. Most infected people have no symptoms but these viruses increase a woman’s risk for cancer of the cervix. The virus can also be transmitted from mother to baby during childbirth. HPV infection is the most common sexually transmitted disease in the United States. It is also the leading cause of abnormal PAP smears and pre-cancerous changes of the cervix in women. There is no cure for genital warts virus infection. Once contracted, the virus can stay with a person for life.
    Genitourinary (GU): Pertaining to the genital and urinary systems.
    Genome: All of the genetic information, the entire genetic complement, all of the DNA possessed by any organism. There is, for example, the human genome, the elephant genome, the mouse genome, the yeast genome, the genome of a bacteria, etc. Humans (and many other higher animals) actually have two genomes—a chromosomal genome and a mitochondrial genome—that together make up their genome.
    Genome, chromosomal: All of the genetic information in the chromosomes of an organism. For humans, that is all of the DNA contained in our normal complement of 46 rod-like chromosomes in virtually every cell in the body. (Mature red blood cells, for one exception, have no nucleus and therefore no chromosomes). The chromosomal genome is synonymous with the nuclear genome. Together with the mitochondrial genome, it constitutes the genome of the human being.
    Genome, human: All of the genetic information, the entire genetic complement, all of the DNA in a person. Humanity’s DNA is the treasury of human inheritance. It is this extraordinary repository of genetic information which the Human Genome Project in the United States and comparable programs in other countries around the world that belong to HUGO (the HUman Genome Organization) are designed to fully fathom.
    Genome, mitochondrial: The genetic information contained in the circular chromosome of the mitochondrion, a structure located outside the nucleus in the cytoplasm of the cell. The mitochondrial genome and the chromosomal (nuclear) genome together constitute the entire genome.
    Genomic library: A collection of clones made from a set of randomly generated overlapping DNA fragments representing the entire genome of an organism. As a molecular genetic sequel to John Steinbeck’s "Of Mice and Men", today you can have a mouse genomic library or a human genomic library.
    GERD: Stands for GastroEsophageal Reflux Disease, a disorder in which there is recurrent return of stomach contents back up into the esophagus, frequently causing heartburn, a symptom of irritation of the esophagus by stomach acid. This can lead to scarring and stricture of the esophagus, which can require stretching (dilating).10% of patients with GERD develop Barrett’s esophagus which increases the risk of cancer of the esophagus. 80% of patients with GERD also have a hiatal hernia.
    Germ cell tumor: A type of brain tumor.
    German measles immunization: The standard MMR vaccine is given to prevent measles, mumps and rubella (German measles). The MMR vaccine is now given in two dosages. The first should be given at12-15 months of age. The second vaccination should be given at 4-6 years (or, alternatively, 11-12 years) of age. Most colleges require proof of a second measles or MMR vaccination prior to entrance. Most children should receive MMR vaccinations. Exceptions may include children born with an inability to fight off infection, some children with cancer, on treatment with radiation or drugs for cancer, on long term steroids (cortisone). People with severe allergic reactions to eggs or the drug neomycin should probably avoid the MMR vaccine. Pregnant women should wait until after delivery before being immunized with MMR. People with HIV or AIDS should normally receive MMR vaccine. Measles, mumps, and rubella vaccines may be administered as individual shots, if necessary, or as a measles-rubella combination.
    Germinoma: A type of germ cell tumor.
    Gestation: From conception to birth.
    Giant cell arteritis: A serious disease characterized by inflammation of the walls of the blood vessels (vasculitis). The vessels affected by the inflammation are the arteries (hence the name "arteritis"). The age of affected patients is usually over 50 years of age. Giant cell arteritis can lead to blindness and/or stroke. It is detected by a biopsy of an artery. Giant cell arteritis is treated with high dose cortisone-related medications. Also called temporal arteritis or cranial arteritis.
    Gingiva: The gum.
    Gingivitis: Gum disease with inflammation of the gums.
    Gland: A group of cells that secrete a substance needed by the body.
    Glandular fever: Glandular fever is infectious mononucleosis. "Mono" and "kissing disease" are popular terms for this very common illness caused by the Epstein-Barr virus (EBV). By the time most people reach adulthood, an antibody against EBV can be detected in their blood meaning they have been infected with EBV. The illness is less severe in young children. The infection can be spread by saliva. The incubation period for "mono" is 4 to 8 weeks. Symptoms include fever, fatigue, sore throat, and swollen lymph glands. "Mono" can cause liver inflammation (hepatitis) and spleen enlargement. Vigorous contact sports should be avoided to prevent spleen rupture.
    Glaucoma: An eye condition in which the fluid pressure inside the eyes rises. Untreated, it leads to vision loss or even blindness. There are several types, including open-angle glaucoma (the common adult-onset) and acute angle-closure glaucoma. The common type of glaucoma, open-angle glaucoma, is an eye disease in which the normal fluid pressure inside the eyes slowly rises, leading to vision loss or even blindness. At the front of the eye, there is a small space called the anterior chamber. Clear fluid flows in and out of the chamber to bathe and nourish nearby tissues. In glaucoma, for still unknown reasons, the fluid drains too slowly out of the eye. As the fluid builds up, the pressure inside the eye rises. Unless this pressure is controlled, it may cause damage to the optic nerve and other parts of the eye and loss of vision. Open-angle glaucoma is so named because the anterior angle of the eye stays open.
    Glaucoma detection: You may know of the "air puff" test or other tests used to measure eye pressure in an eye examination. But, this test alone cannot detect glaucoma. Glaucoma is found most often during an eye examination through dilated pupils after drops are put into the eyes during the exam to enlarge the pupils. This allows the eye care professional to see more of the inside of the eye to check for signs of glaucoma.
    Glaucoma, risk factors: if you belong to a high-risk group for glaucoma, have your eyes examined through dilated pupils every 2 years by an eye care professional. High-risk groups include everyone with a family history of glaucoma, everyone over the age of 60 and any Black over the age of 40. (Among Blacks, studies show that glaucoma is: 5 times more likely to occur in Blacks than in Whites and about 4 times more likely to cause blindness in Blacks than in Whites).
    Glaucoma, symptoms of: At first, there are no symptoms. Vision stays normal, and there is no pain. However, as the disease progress, a person with glaucoma may notice the side vision gradually failing. That is, objects in front may still be seen clearly, but objects to the side may be missed. As the disease worsens, the field of vision narrows and blindness results.
    Glaucoma treatment (laser): A laser beam of light is focused on the part of the anterior chamber where the fluid leaves the eye. This results in a series of small changes, which makes it easier for fluid to exit the eye. Over time, the effect of laser surgery may wear off. Patients who have this form of surgery may need to keep taking glaucoma drugs.
    Glaucoma treatment (medical): Although glaucoma cannot be cured, it can usually be controlled. Medical treatment can be in the form of eyedrops or pills. Some drugs are designed to reduce pressure by slowing the flow of fluid into the eye, while others help to improve fluid drainage. The regular use of medications usually controls the increased fluid pressure. However, these drugs may stop working over time or they may cause side effects so that the eye care professional may select other drugs, change the dose, or use other means to deal with the glaucoma.
    Glaucoma treatment (surgery): Surgery can also help fluid escape from the eye and thereby reduce the pressure. However, surgery is now usually reserved for patients whose pressure cannot be controlled with eyedrops, pills, or laser surgery.
    Glioblastoma multiforme: A type of brain tumor.
    Glioma: A name for brain tumors that begin in the glial cells, or supportive cells, in the brain. "Glia" is the Greek word for glue.
    Glossitis: Inflammation of the tongue.
    Glottis: The middle part of the larynx; the area where the vocal cords are located.
    Glucocerebrosidase deficiency: Causes Gaucher’s disease (type 1), a progressive genetic disease due to an enzyme defect. The enzyme, glucocerebrosidase, is needed to break down the chemical glucocerebroside. The enzyme defect in persons with Gaucher’s disease (GD) leads to the accumulation of glucocerebroside in the spleen, liver, and lymph nodes. The most common early sign is enlargement of the spleen (located in the upper left abdomen). Other signs include low red blood cell counts (anemia), a decrease in blood clotting cells (platelets), increased pigmentation of the skin, and a yellow fatty spot on the white of the eye (a pinguecula). Severe bone involvement can lead to pain and collapse of the bone of the hips, shoulders, and spine. The GD gene is on chromosome 1. The disease is a recessive trait. Both parents carry a GD gene and transmit it for their child with the disease. The parents’ risk of a child with the disease is 1 in 4 with each pregnancy. This type of Gaucher’s disease (noncerebral juvenile Gaucher’s disease) is most common in Ashkenazi Jews (of European origin) and is the most common genetic disease among Jews in the United States.
    Glucose: The sugar that is the chief source of energy.
    Glucocorticoid: A hormone that predominantly affects the metabolism of carbohydrates and,to a lesser extent, fats and proteins (and has other effects). Glucocorticoids are made in the outside portion (the cortex) of the adrenal gland and chemically classed as steroids. Cortisol is the major natural glucocorticoid. The term glucocorticoid also applies to equivalent hormones synthesized in the laboratory.
    Glucose-6-phosphate dehydrogenase (G6PD): Deficiency of G6PD is the commonest disease-causing enzyme defect in humans affecting an estimated 400 million people. The G6PD gene is on the X chromosome. Males with the enzyme deficiency develop anemia due to breakup of their red blood cells when they are exposed to oxidant drugs such as the antimalarial primaquine, the sulfonamide antibiotics or sulfones, naphthalene moth balls, or fava beans.
    Glucose tolerance test (GTT): After fasting, a specific amount (100 grams) of glucose is given by mouth, and the blood levels of this sugar are measured every hour. Normally, the blood glucose should return to normal within 2 to 2 ½ hours. The GTT is considered a classic test of carbohydrate metabolism. It is much used in the diagnosis of diabetes. The GTT depends on a number of factors including the ability of the intestine to absorb glucose, the power of the liver to take up and store glucose, the capacity of the pancreas to produce insulin, and the amount of "active" insulin.
    Gluteal: Pertaining to the buttock region formed by the gluteal muscles (gluteus maximus, medius, and minimus).
    Gluten: A protein found in wheat or related grains and many foods that we eat. Gluten can be found in a large variety of foods including soups, salad dressings, processed foods and natural flavorings. Unidentified starch, binders and fillers in medications or vitamins can be unsuspected sources of gluten.
    Gluten enteropathy: A condition also called celiac sprue whereby the absorption of food nutrients through the small intestine is impaired because of an immune (allergic) reaction to gluten, a protein found in wheat or related grains and many other foods. Frequent diarrhea and weight loss can be symptoms. A skin condition called dermatitis herpetiformis can be associated with celiac sprue. The most accurate test for the condition is a biopsy of the involved small bowel. Treatment is avoidance of gluten in the diet. For stubborn sprue, medications are used.
    Goiter: Enlargement of the thyroid gland. A goiter is not cancerous. A goiter can be associated with normal, elevated (hyperthyroidism) or decreased (hypothyroidism) thyroid hormone levels in the blood.
    Goiter, diffuse toxic: Graves’ disease, the most common cause of hyperthroidism, too much thyroid hormone.
    Goiter, iodide: Just as too little iodine can cause thyroid disease, so may prolonged intake of too much iodine also lead to the development of goiter (swelling of the thyroid gland) and hypothyroidism (abnormally low thyroid activity). Certain foods and medications contain large amounts of iodine. Examples include seaweed; iodine-rich expectorants (such as SSKI and Lugol’s solution) used in the treatment of cough, asthma, chronic pulmonary disease; and amiodarone (Cardorone), an iodine-rich medication used in the control of abnormal heart rhythms (cardiac arrhythmias).
    Goiter, toxic multinodular: Condition in which the thyroid gland contains multiple lumps (nodules) that are overactive and produce excess thyroid hormones. This condition is also known as Parry’s disease or Plummer’s disease.
    Golfer’s cramp: A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs when playing golf. Similar focal dystonias have also been called typist’s cramp, pianist’s cramp, musician’s cramp, and writer’s’s cramp. Golfer’s cramp provides a reason to switch to tennis (and get tennis elbow).
    "Good" cholesterol: High-density lipoprotein (HDL) cholesterol.
    Gonadotropin, human chorionic (hCG): A human hormone made by chorionic cells (in the fetal part of the placenta), hCG is directed at the gonads and stimulates them. hCG becomes detectable (by immunologic means) within days of fertilization and forms the foundation of the common pregnancy tests. The level of hCG in maternal serum also enters as one component in the "double" and the "triple" screens used during pregnancy to assign risks of Down syndrome and other fetal disorders.
    Gonorrhea: A bacterial infection transmitted by sexual contact. Gonorrhea is one of the oldest known sexually transmitted diseases (STDs). In women infected with this bacteria (Neisseria gonorrhoeae), 25-40% will also be infected with another bacteria that can cause another STD called chlamydia. Gonorrhea is NOT transmitted from toilet seats. More than half of women infected with gonorrhea do not have any symptoms. If symptoms occur, they may include burning or frequent urination, yellowish vaginal discharge, redness and swelling of the genitals, and a burning or itching of the vaginal area. Untreated, gonorrhea can lead to severe pelvic infections.
    Gottron's sign: Gottron's sign is a scaly, patchy redness over the knuckles and is seen in patients with dermatomyositis, an inflammatory muscle disorder. (see polymyositis).
    Gout: Condition characterized by abnormally elevated levels of uric acid in the blood, recurring attacks of joint inflammation (arthritis), deposits of hard lumps of uric acid in and around the joints, and decreased kidney function and kidney stones. Uric acid is a breakdown product of purines, that are part of many foods we eat. The tendency to develop gout and elevated blood uric acid level (hyperuricemia) is often inherited and can be promoted by obesity, weight gain, alcohol intake, high blood pressure, abnormal kidney function, and drugs. The most reliable diagnostic test for gout is the identification of crystals in joints, body fluids and tissues.
    Gout, tophaceous: A form of chronic gout. Nodular masses of uric acid crystals (tophi) are deposited in different soft tissue areas of the body. Even though tophi are most commonly found as hard nodules around the fingers, at the tips of the elbows, and around the big toe, tophi nodules can appear anywhere in the body. They have been reported in unexpected areas such as in the ears, vocal cords, or around the spinal cord!
    Gouty arthritis: An attack that is usually extremely painful of joint inflammation due to deposits of uric acid crystals in the joint fluid (synovial fluid) and joint lining (synovial lining). Intense joint inflammation occurs as white blood cells engulf the uric acid crystals, causing pain, heat, and redness of the joint tissues. The term "gout" commonly is used to refer to these painful arthritis attacks but gouty arthritis is only one manifeatation of gout.
    Graft: Healthy skin, bone, or other tissue taken from one part of the body to replace diseased or injured tissue removed from another part of the body.
    Graft-versus-host disease: A reaction of donated bone marrow against a patient's own tissue. Also called GVHD.
    Granuloma: Any of a number of forms of localized nodular inflammation in tissues which have a typical pattern when the involved tissue examined under a microscope. Granulomas typically are caused by a variety of chemical, biologic, or physical irritants of the tissue.
    Granuloma, fish bowl: Localized nodular skin inflammation (small reddish raised areas of skin) caused by a bacterium called mycobacterium marinum. Fish bowl granuloma is typically acquired by occupational or recreational exposure to salt or fresh water, often resulting from minor trauma during caring for aquariums. The diagnosis is suggested by the history of exposure and confirmed by culturing tissue specimens which yield the microscopic organism, mycobacterium marinum. The infection can be treated with a variety of antibiotics, including doxycycline, minocycline, clarithromycin, rifampin, and trimethoprim-sulfamethoxazole. Also called "swimming pool granuloma."
    Granuloma, swimming pool: Localized nodular skin inflammation (small reddish raised areas of skin) caused by a bacterium called mycobacterium marinum. Swimming pool granuloma is typically acquired by occupational or recreational exposure to salt or fresh water, often resulting from minor trauma during caring for aquariums. The diagnosis is suggested by the history of exposure and confirmed by culturing tissue specimens which yield the microscopic organism, mycobacterium marinum. The infection can be treated with a variety of antibiotics, including doxycycline, minocycline, clarithromycin, rifampin, and trimethoprim-sulfamethoxazole. Also called "fish bowl granuloma."
    Granulomatous enteritis: Crohn’s disease, a chronic inflammatory disease of the intestine primarily in the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition with periods of remission and exacerbation. In the early stages, Crohn’s disease causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs.When only the large intestine (colon) is involved, the condition is called Crohn’s colitis. When only the small intestine is involved, the condition is called Crohn’s enteritis. When only the end of the small intestine (the terminal ileum) is involved, it is termed terminal ileitis. When both the small intestine and the large intestine are involved, the condition is called Crohn’s enterocolitis (or ileocolitis). Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery. (The disease is also called regional enteritis).
    Granulomatous ileitis: Crohn’s disease involving the ileum (the lowest portion of the small intestine).
    Graves’ disease: The most common cause of hyperthyroidism (too much thyroid hormone), Graves’ disease is due to a generalized (diffuse) overactivity (toxic) of the whole enlarged thyroid gland (goiter); it is also commonly known as diffuse toxic goiter. There are three components to Graves’ disease: hyperthyroidism, protrusion of the eyes (ophthalmopathy), and skin lesions (dermopathy). Ophthalmopathy can cause sensitivity to light and a feeling of "sand in the eyes." With further protrusion of the eyes, double vision and vision loss may occur. The ophthalmopathy tends to worsen with smoking. Dermopathy is a rare, painless, reddish lumpy skin rash that occurs on the front of the leg. Graves’ disease can run in families. Factors that can trigger Graves’ disease include stress, smoking, radiation to the neck, medications (such as interleukin-2 and interferon-alpha), and infectious organisms such as viruses. Graves’ disease can be diagnosed by a typical thyroid scan (diffuse increase uptake), the characteristic triad of ophthalmopathy, dermopathy, and hyperthyroidism, or blood testing for TSI (Thyroid Stimulating Immunoglobulin) level which is abnormally high.
    Gray matter: The cortex of the brain which contains nerve cell bodies. The gray matter is in contrast to the white matter, the part of the brain that contains myelinated nerve fibers. The gray matter is so named because it in fact appears gray. The white matter is white because that is the color of myelin, the insulation covering the nerve fibers. In "The Mysterious Affair at Styles" (1920), Agatha Christie first quoted the fictional Belgian detective Hercule Poirot in regard to his gray matter: "’This affair must be unravelled from within.’ He tapped his forehead. ‘These little grey cells. It is "up to them"—as you say over here.’"
    Groin: The area where the thigh meets the hip.
    Growing pains: Mysterious pains in growing children, usually in the legs. These pains are similar to what the weekend gardener suffers from on Monday—an overuse type of problem. If in playing, children exceed their regular threshold, they will be sore, just like an adult. Growing pains are typically somewhat diffuse (vs. focal) and are not associated with physical changes of the area (such as swelling, redness, etc.). The pains are usually easily relieved by Messages, Tylenol (acetaminophen), or rest. If the pains persist past a week or there are physical changes, the child should be seen by a physician.
    Guanine (G): One member of the base pair G-C (guanine-cytosine) in DNA.
    Gum disease: Inflammation of the soft tissue (gingiva) and abnormal loss of bone that surrounds the teeth and holds them in place. Gum disease is caused by toxins secreted by bacteria in "plaque" that accumulate over time along the gum line. This plaque is a mixture of food, saliva, and bacteria. Early symptoms of gum disease include gum bleeding without pain. Pain is a symptom of more advanced gum disease as the loss of bone around the teeth leads to the formation of gum pockets. Bacteria in these pockets cause gum infection, swelling, pain, and further bone destruction. Advanced gum disease can cause loss of otherwise healthy teeth.
    Gynecologic oncologists: Doctors who specialize in treating cancers of the female reproductive organs.
    Gynecologist: A doctor who specializes in treating diseases of the female reproductive organs.
    Gynecology: The word comes from the Greek gyno, gynaikos meaning woman + logia meaning study, so gynecology literally is the study of women. However, these days gynecology does not address all of women’s medicine but focuses on disorders of the female reproductive organs.

    Gynecomastia: Excessive development of the male breasts. Temporary enlargement of the breasts is not unusual or abnormal in boys during adolescence or during recovery from malnutrition. Gynecomastia may be abnormal as, for example, in Klinefelter’s syndrome.
  • H. flu: See Haemophilus influenzae type b.
    H. flu immunization: See HIB immunization.
    Haemophilus influenzae (also H. flu): (Not the cause of influenza as it was once thought to be), H. flu is a bacteria capable of causing ear infections, meningitis, cellulitis (soft tissue infection), upper respiratory infections, pneumonia and other infections, especially in young children.
    Haemophilus influenzae type B immunization: See HIB immunization,
    Hair follicle: A sac from which a hair grows.
    Hairy cell leukemia: A rare type of chronic leukemia in which the abnormal white blood cells appear to be covered with tiny hairs. Hammer toe: A flexed (curly) toe but with no abnormal rotation of the toe. May require surgical correction.
    Hansen disease: Leprosy.
    Haploid: A set of chromosomes with only one member of each chromosome pair. The sperm and egg are haploid and, in humans, have 23 chromosomes.
    Hard palate: The bony part of the roof of the mouth. The hard palate is the front of the palate and is in front of the soft palate.
    HAVRIX: A vaccine against hepatitis A made of killed hepatitis A virus to stimulate the body’s immune system to produce antibodies against the hepatitis A virus.
    Hay fever: Allergic rhinitis.
    HBIG: Hepatitis B immune globulin, which contains antibodies to hepatits B virus and offers prompt but short lived protection.
    hCG: Human chorionic gonadotropin, a human hormone produced by the fetal part of the placenta that stimulates the gonads. The abbreviation can also be written entirely in capital (upper case) letters as "HCG". For more on this hormone in key lab tests, please see: Human chorionic gonadotropin.
    Hct: Hematocrit.
    HDL: High-density lipoprotein.
    HDL cholesterol: High-density lipoprotein cholesterol (the "good" cholesterol).
    Health care proxy: A health care proxy is one form of advance medical directive. Advance medical directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There are two basic forms of advance directives: (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for healthcare decision-making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society).
    Heart: The heart is a muscle which pumps blood it receives from veins into arteries throughout the body. The heart is composed of specialized muscle called "cardiac muscle." (see muscle). The heart, veins and arteries make up the circulatory system.
    Heart attack: A coronary artery occlusion or myocardial infarction (MI).
    Heart block: A block in the conduction of the normal electrical impulses in the heart.
    Heartburn: Heartburn has nothing to do with the heart. It is an uncomfortable feeling of burning and warmth occurring in waves rising up behind the breastbone (sternum) toward the neck. It is usually due to gastroesophageal reflux, the return of stomach acid back up into the esophagus, the soft tube-like portion of the digestive tract connecting the pharynx with the stomach.
    Heart failure: Inability of the heart to keep up with the demands on it and pump the blood with normal efficiency.
    Heart murmur: An unusual heart sound which may be innocent or reflect disease.
    Heart rate: The number of heart beats per unit time, usually per minute. The heart rate is based on the number of contractions of the ventricles (the lower chambers of the heart). The heart rate may be too fast (tachycardia) or too slow (bradycardia). The pulse is bulge of an artery from the wave of blood coursing through the blood vessel as a result of the heart beat. The pulse is often taken at the wrist to estimate the heart rate.
    Hecht syndrome: Inherited disorder transmitted as an autosomal dominant trait in which short tight muscles make it impossible to open the mouth fully or keep the fingers straight when the hand is flexed back. The small mouth creates feeding problems. The hands may be so tightly fisted the infant crawls on the knuckles. Also called the trismus pseudocamptodactyly syndrome.
    Helicobactor pylori: Bacteria that cause inflammation and ulcers in the stomach.
    Hemangioma: A birth irregularity where a localized tissue mass grows rich in small blood vessels. Capillary hemangiomas are composed nearly entirely of tiny capillary vessels. Cavernous hemangiomas are composed of blood-filled "lakes" and channels.
    Hemarthrosis: Blood in a joint.
    Hematemesis: Bloody vomit.
    Hematocrit: The percentage, by volume, of red cells in blood. Normal range for males is about 40-54 and for females 37-47 (values may vary slightly between laboratories).
    Hematologist: A doctor who specializes in treating diseases of the blood.
    Hematoma: A hematoma is a localized swelling filled with blood. The blood is usually clotted or partially clotted and exists within an organ or a soft tissue space, such as muscle.
    Hematopoiesis: The formation and development of blood cells.
    Hematuria: Blood in the urine.
    Hemiparesis: Weakness on one side of the body.
    Hemiplegia: One side of the body is paralyzed.
    Hemizygous: Having only a single set of genes as, for example, on the single X chromosome in the male.
    Hemodialysis: Filtration and cleansing of the blood. Commonly called dialysis.
    Hemoglobin: The oxygen-carrying pigment of red blood cells.
    Hemoglobin A: The main type of hemoglobin after early infancy. The A stands for Adult.
    Hemoglobin F: The main type of hemoglobin in the fetus and still at birth. The F stands for Fetal.
    Hemoglobin S: The most common type of abnormal hemoglobin, hemoglobin S is found in sickle cell trait and sickle cell anemia. It differs from hemoglobin A only by a single amino acid substitution. Recognition of this tiny change marked the opening of molecular medicine.
    Hemoglobinuria: Hemoglobin in the urine.
    Hemolysis: Breakdown of red blood cells.
    Hemolytic anemia: Anemia due to the destruction (rather than underproduction) of red blood cells.
    Hemolytic disease of the newborn: Abnormal breakup of red blood cells in the fetus or newborn.
    Hemophilia: A set of bleeding disorders.
    Hemophilia A: Classic hemophilia (the disease of the Russian royal house and other descendants of Queen Victoria). Due to profound deficiency of factor VIII which is necessary for normal blood clotting. The hemophilia A gene is on the X chromosome so females carry the gene and each of their sons stands a 50% chance of receiving the gene and having hemophilia. Treatment of hemophiliacs with contaminated blood products exposed many to HIV.
    Hemophilia B: Also called Christmas disease (so-named for the first patient studied in detail with the disease). Due to deficiency of coagulation factor IX. The hemophilia B gene is also on the X chromosome.
    Hemoptysis: Spitting up blood or blood-tinged sputum.
    Hemorrhage: Hemorrhage refers to bleeding or a flow of blood. It can be internal, and not be visible, or external, and therefore, visible on the body.
    Hemorrhoids: Dilated veins around the rectum.
    Heparin: An anticoagulant (anti-clotting) medication. Heparin is useful in preventing thromboembolic complications (clots that travel from their site of origin through the blood stream to clog up another vessel). Heparin is also used in the early treatment of blood clots in the lungs (pulmonary embolisms).
    Hepatic: Having to do with the liver.
    Hepatitis: Inflammation of the liver.
    Hepatitis A: Hepatitis due to the hepatitis A virus which is usually transmitted by poor hygiene. (One reason why food service employees are required to wash their hands after using the toilet.)
    Hepatitis A immunization: When immediate protection against hepatitis A (infectious hepatitis) is needed, immunoglobulins are used. Protection is effective only if given within 2 weeks of exposure and lasts but 2-4 months. Immunoglobulins can be used to protect household contacts of someone with acute viral hepatitis and travelers to regions with poor sanitation and high hepatitis A rates, when the traveler has to depart sooner than the vaccines can take effect (about 2 weeks). Travelers can receive the immunoglobulin and vaccine simultaneously and be protected immediately and for longer term. When immediate protection is not needed, hepatitis A vaccines are considered for individuals in high-risk settings, including frequent world travelers, sexually active individuals with multiple partners, homosexual men, individuals using illicit drugs, employees of daycare centers, and certain healthcare workers, and sewage workers. Two hepatitis A vaccines called HAVRIX and VAQTA are commercially available in the U.S. Both are highly effective and provide protection even after only one dose. Two doses are recommended for adults and 3 doses for children (under 18 years of age) to provide prolonged protection.
    Hepatitis B: Hepatitis due to the hepatitis B virus once thought to be passed only through blood products and so called serum hepatitis. Now known to be passed also by needle sticks, body piercing and tattooing (if proper sterilization or disposable one-use instruments are not used), dialysis, sexual and even less intimate close contact, and childbirth.
    Hepatitis B immunization: Hepatits B (hep B) vaccine gives prolonged protection, but 3 shots over a half year are usually required. In the U.S., all infants receive hep B vaccine. Two vaccines (ENGERIX-B, and RECOMBIVAX-HB) are available in the US. The first dose of hep B vaccine is frequently given while the newborn is in the hospital or at the first doctor visit following birth. The second dose is given about 30 days after the initial dose. A booster dose is performed approximately six months later. Babies born to mothers testing positive for hep B receive, in addition, HBIG (hep B immune globulin) for prompt protection. Older children (11-12 years) are advised to receive a hep B booster as are adults in high-risk situations including healthcare workers, dentists, intimate and household contacts of patients with chronic hep B infection, male homosexuals, individuals with multiple sexual partners, dialysis patients, IV drug users, and recipients of repeated transfusions. Healthcare workers accidentally exposed to materials infected with hep B (such as needle sticks), and individuals with known sexual contact with hep B patients are usually given both HBIG and vaccine to provide immediate and long term protection.
    Hepatitis C: Hepatitis due to the hepatitis C virus (HCV) which is usually spread by blood transfusion, hemodialysis, and needle sticks. Causes most transfusion-associated hepatitis. Transmission of the virus by sexual contact is rare. At least half of patients develop chronic hepatitis C infection. Hepatitis C was previously called "non-A, non-B hepatitis.
    Hepatitis D, E, F, and G: Lesser known (than hepatitis A, B, and C), the most significant of these seems to be type D, or the delta agent, which only causes disease in the presence of the hepatitis B virus.
    Hepatitis, infectious: See Hepatitis A.
    Hepatitis, non-A, non-B: The old name for hepatitis C when the causative virus had not been identified but it was known not to be hepatitis A or B.
    Hepatitis, viral: Liver inflammation caused by viruses. Specific hepatitis viruses have been labeled A, B, C, D, E, F, and G. While other viruses, such as the mononucleosis (Epstein-Barr) virus and cytomegalovirus, can also cause hepatitis, the liver is not their primary target.
    Hepatomegaly: An enlarged liver.
    Hepatosplenomegaly: Enlargement of the liver and spleen.
    Hepatotoxic: Injurious to the liver. For example, acetaminophen (TYLENOL) can be hepatotoxic.
    Herbalist: One versed in herbal lore and, in regard to therapy, an herb doctor.
    Heritable: Capable of being transmitted from parent to child.
    Heritability: The degree to which something is inherited.
    Hereditary angioedema: A genetic form of angioedema. (Angioedema is also referred to as Quinke’s disease.) Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks. Also called hereditary angioneurotic edema.
    Hereditary angioneurotic edema: A genetic form of angioedema. (Angioedema is also referred to as Quinke’s disease.) Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks. Also called hereditary angioedema.
    Hereditary mutation: A gene change that occurs in a germ cell (an egg or sperm) to become incorporated in every cell in the body. Hereditary mutations (also called germline mutations) play a role in cancer as, for example, the eye tumor retinoblastoma and Wilms' tumor of the kidney.
    Hereditary spherocytosis (HS): Genetic disorder of red blood cells. In HS, the red cells are abnormal in shape. They are spherical rather than the normal svelt biconcave-disk shape. They are also unusually fragile. The rotund HS red cells tend to get trapped in narrow blood passages (such as in the spleen) and break up (hemolyze) easily, leading to anemia.
    Heredity: Genetic transmission from parent to child.
    Hernia: Also called rupture, "hernia" is a general term referring to a protrusion of a tissue through the wall of the cavity in which it is normally contained.
    Hernia, hiatus: Protrusion of the stomach up into the opening normally occupied by the esophagus in the diaphragm, the muscle that separates the chest (thoracic) cavity from the abdomen. Hiatus in Latin means an opening.
    Herniation: Abnormal protrusion of tissue through an opening. For example, a intervertebral disk (one situated between the vertebral bodies) can protrude and impinge on a nerve root.
    Heroin: Semisynthetic drug derived from morphine. Discovered in 1874, it was introduced commercially in 1898 by the Bayer company in Germany. The name heroin was coined from the German heroisch meaning heroic, strong. Heroin is stronger (more potent) than morphine.
    Herpes, genital: A viral infection transmitted through intimate contact with the moist mucous linings of the genitals. This contact can involve the mouth, the vagina or the genital skin. The herpes simplex type 2 virus enters the mucous membranes through microscopic tears. Once inside, the virus travels to nerve the roots near the spinal cord and settles there permanently. When an infected person has a herpes outbreak, the virus travels down the nerve fibers to the site of the original infection and when it reaches the skin, the classic redness and blisters occur. The outbreak of herpes is closely related to the functioning of the immune system. Women who have suppressed immune systems, either through stress, disease, or medications, have more frequent and longer-lasting outbreaks. Commonly just called "herpes."
    Herpes simplex type 1: A virus that causes cold sores and fever blisters.
    Herpes simplex type 2: Different from herpes simplex type 1, herpes simplex 2 causes genital herpes.
    Herpesvirus: A member of the herpes family of viruses. One type of herpesvirus is sexually transmitted and causes sores on the genitals.
    Herpes zoster: Also called shingles, zona, and zoster. The culprit is the varicella-zoster virus. Primary infection with this virus causes chickenpox (varicella). At this time the virus infects nerves (namely, the dorsal root ganglia) where it remains latent (lies low) for years. It can then be reactivated to cause shingles with blisters over the distribution of the affected nerve accompanied by often intense pain and itching.
    Hetero-: Combining form from the Greek heteros meaning different. The opposite is homo- from the Greek homos meaning same. For example, heterogeneous and homogeneous, heterosexual and homosexual, etc.
    Heterochromatin: A genetically inactive part of the genome, heterochromatin was so named because it was chromosomal material (chromatin) that stained differently, more darkly, all through the cell cycle, than most chromosomal material (which was named euchromatin). There are two types, namely constituitive heterochromatin and facultative heterochromatin.
    Heterochromatin, constituitive: Heterochromatin that is fixed and irreversible. Regions of constituitive heterochromatin are located at very specific spots in the genome (on chromosomes 1, 9, 16 and the Y chromosome, the tiny short arms of chromosomes 13-15 and 21 and 22, and near the centromeres of chromosomes) and consists of DNA that contains many tandem (not inverted) repeats of a short basic repeating unit (known as satellite DNA).
    Heterochromatin, facultative: Heterochromatin that need not always be heterochromatic but has the faculty to return to the normal euchromatic state. The inactive X chromosome is made up of facultatative heterochromatin. When a woman transmits that X to a son, it reverts to euchromatin and genetic activity.
    Heterochromia: Different colors.
    Heterochromia iridis: A difference of color between the iris of one eye and the other. (A person with one brown and one blue eye has heterochromia iridis.) Also, a difference in color within an iris (sectoral heterochromia iridis).
    Heteroerotic: Having to do with sexual excitement toward the opposite sex. By contrast with alloerotic.
    Heterokaryon: A cell with two separate nuclei formed by the experimental fusion of two genetically different cells. (Heterokaryons, for example, composed of nuclei from Hurler syndrome and Hunter syndrome, both diseases of mucopolysaccharide metabolism, have normal mucopolysaccharide metabolism proving that the two syndromes affect different proteins and so can correct each other in the heterokaryon).
    Heteromorphism: Something different in form. Chromosome heteromorphisms are normal variations in the appearance of chromosomes.
    Heteroploid: A different chromosome number than the normal number of chromosomes.
    Heterosexual: A person sexually attracted to persons of the opposite sex. The word "straight" has become synonymous with heterosexual. Heterosexual can also be an adjective.
    Heterosexuality: Sexuality directed toward someone of the opposite sex.
    Heterozygote: An individual with different genes at a particular spot (locus) on a pair of chromosomes. (A heterozygote for cystic fibrosis (CF) has the CF gene on one chromosome 7 and the normal paired gene on the other chromosome 7. That makes them a carrier for CF.)
    Heterozygous: The state of being heterozygous.
    Hexoseaminidase A: Deficiency of this enzyme causes Tay-Sachs disease, a progressive, fatal neurologic disorder concentrated in people of European Jewish (Ashkenazi) descent.
    Hiatus hernia: Protrusion of the stomach up into the opening normally occupied by the esophagus in the diaphragm, the muscle that separates the chest (thoracic) cavity from the abdomen. Hiatus in Latin means an opening.
    HIB: Haemophilus influenzae type b.
    HIB immunization: This vaccine is to prevent disease caused by the Haemophilus influenzae type B (HIB) bacteria. The H. influenzae (H. flu) bacteria can cause a range of serious diseases including meningitis with potential brain damage and epiglottitis with airway obstruction poisoning. The HIB vaccine is usually given at 2, 4 and 6 months of age. A final booster is given at 12-15 months of age. HIB vaccine rarely causes severe reactions.
    Hiccups: Spasmodic contractions of the diaphragm that are involuntary and often rhythmic. Usually just a minor nuisance, prolonged hiccups can become a major problem.
    Hidradenitis suppurativa: This is an illness characterized by multiple abscesses that form under the arm pits and in the groin area.
    High blood pressure: A repeatedly elevated blood pressure exceeding 140 over 90 mmHg. High blood pressure (hypertension) is "the silent killer." Chronic high blood pressure can stealthily cause blood vessel changes in the back of the eye (retina), abnormal thickening of the heart muscle, kidney failure, and brain damage. No specific cause for high blood pressure is found in 95% of patients. High blood pressure is treated with salt restriction, regular aerobic exercise, and medications.
    Hippocampus: An area buried deep in the forebrain that helps regulate emotion and memory.
    Hip bursitis: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are two major bursae of the hip. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery.
    Hip pointer: Sportstalk for an iliac crest contusion (a bruise of the upper edge of the ilium, one of the hip bones).
    Hirschsprung's disease: Absence of nerves (ganglia) in the bowel wall starting in the anus and extending up a variable distance with enlargement of the bowel above that point. Hirschsprung's disease is the commonest cause of lower intestinal obstruction in the newborn and, later, one of the causes of chronic constipation. Also called congenital aganglionic megacolon.
    Hirsute: Overly hairy.
    Hirudin: An anticoagulant (anti-clotting) agent that prevents thromboembolic complications (clots that travel through the blood stream to clog up a vessel). Hirudin is the active principle in the secretion of leeches. Desirudin and lepirudin (REFLUDAN) are genetically engineered recombinant forms of hirudin.
    Histoplasma: A fungus found worldwide. In the USA, it is so common in the Midwest that in parts of Kentucky and Tennessee nearly 90% of adults show evidence of exposure (with a positive histoplasma skin test).
    Histoplasmosis: Infection with histoplasma. Most patients have no symptoms However, histoplasma can cause acute or chronic lung disease or progessive disseminated histoplasmosis (a particular hazard for persons with HIV).
    Histamine: Substance that plays a major role in many allergic reactions. Histamine dilates blood vessels and makes the vessel walls abnormally permeable.
    Histocompatible: The prefix histo- means tissue. The term histocompatible is literally tissue compatible. If a donor and recipient are histocompatible (like identical twins), a transplant will be easily accepted.
    Histones: Proteins associated with DNA in chromosomes.
    History: In medicine, the patient's past and present which may hopefully contain clues helpful to their future health.
    HIV: Acronym for the Human Immunodeficiency Virus, the cause of AIDS.
    Hives: Urticaria. Raised, itching areas of skin, often a sign of an allergic reaction. Also called "welts" or "nettle rash."
    HLA: The HLA complex is the major human histocompatibility system. HLA-typing is done before transplantation to determine the degree of histocompatability. HLA is an acronym for Human Leukocyte Antigens).
    Hodgkin's disease (Hodgkin's lymphoma): A disease of the lymph nodes named after the English physician Thomas Hodgkin (1798-1866) who discovered it. ("Perfecting the World" is an excellent biography of Dr. Hodgkin by A. M. and E. H. Kass).
    Homeobox: A short stretch of nucleotides (DNA or RNA) with an almost identical base sequence in all genes that contain that stretch. Homeoboxes occur in many organisms from fruit flies to human beings and appear to determine when particular groups of genes are expressed during development.
    Homeopath: A person who practices homeopathy.
    Homeopathy: A system of therapy founded in the 19th century based on the concept that disease can be treated with drugs (in minute doses) thought capable of producing the same symptoms in healthy people as the disease itself.
    Homocystinuria: A genetic disease due to an enzyme deficiency. Among other events, there is a buildup of the amino acid homocystine. Progressive mental retardation is common in untreated cases. The finding of vascular disease and premature arteriosclerosis in persons with homocystinuria led to the theory that homocystine may be a factor in heart disease.
    Homolog (homologue): One chromosome of a pair.
    Homologies: Similarities in DNA or protein sequences between individuals or between species.
    Homologous: The relationship between two chromosomes that are paired and so are homologs of each other.
    Homologous chromosomes: A pair of chromosomes containing the same gene sequences, each derived from one parent.
    Homosexual: A person sexually attracted to persons of the same sex. Homosexuals include males (gays) and females (lesbians). Homosexual can also be an adjective.
    Homosexuality: Sexuality directed toward someone of the same sex.
    Hormone: Chemical substance produced in the body that controls and regulates the activity of certain cells or organs. A hormone originally denoted a chemical made by a special gland for export to another part of the body. Now a hormone is more broadly any chemical, irrespective of whether it is produced by a special gland or not, for export or domestic use, that "controls and regulates the activity of certain cells or organs.". The word "hormao" which means "I set in motion" or "I stir up" was used in ancient Greece to covey the "vital principle" of "getting the juices flowing." The word "hormone" was resurrected in 1902 (not 1906, as the Oxford English Dictionary states) by the English physiologists Wm. M. Bayliss and Ernest H. Starling who that year reported their discovery of a substance made by glands in the small intestine that stimulated pancreatic secretion. They called the substance "secretin" and dubbed it a "hormone", the first known hormone.
    Hormone, aldosterone: Hormone produced by the outer portion (cortex) of the adrenal gland that regulates the balance of water and electrolytes (ions such as potassium and sodium) in the body. Aldosterone encourages the kidney to excrete potassium into the urine and to retain sodium, thereby retaining water. Aldosterone is classified as a mineralocorticoid hormone.
    Hormone, androgenic: Any hormone that promotes the development and maintenance of male sex characteristics. Testosterone is an androgen.
    Hormone, cortisol: The primary stress hormone. Cortisol is the major natural glucocorticoid in humans.
    Hormone, estrogenic: A female hormone produced by the ovaries (or an equivalent hormone synthesized in the laboratory). Estrogen deficiency can lead to osteoporosis.
    Hormone, glucocorticoid: A hormone that predominantly affects the metabolism of carbohydrates and,to a lesser extent, fats and proteins (and has other effects). Glucocorticoids are made in the outside portion (the cortex) of the adrenal gland and chemically classed as steroids. Cortisol is the major natural glucocorticoid. The term glucocorticoid also applies to equivalent hormones synthesized in the laboratory.
    Hormone, human chorionic gonadotropin (hCG): A human hormone made by chorionic cells (in the fetal part of the placenta), hCG is directed at the gonads and stimulates them. hCG becomes detectable (by immunologic means) within days of the time of fertilization. It therefore forms the foundation of most common pregnancy tests. The level of hCG in maternal serum enters as one component in the "double" and the "triple" screens used during pregnancy to assign risks of Down syndrome and other fetal disorders.
    Hormone, mineralocorticoid: A group of hormones, the most important being aldosterone, that regulate the balance of water and electrolytes (ions such as sodium and potassium) in the body. The mineralocorticoid hormones act specifically on the tubules of the kidney.
    Hormone, parathormone: Hormone made by the parathyroid gland (behind the thyroid gland in the neck). Parathormone (pronounced para-thor-mone) is critical to calcium and phosphorus balance. Deficiency of parathormone results in abnormally low calcium in the blood (hypocalcemia). Also call parathyrin.
    Hormone, parathyrin: See Hormone, parathormone.
    Hormone, parathyroid: See Hormone, parathormone.
    Hormone, progesterone: A female hormone, progesterone is the principal progestational hormone. Progestational hormones prepare the uterus (the womb) to receive and sustain the fertilized egg.
    Hormone, secretin: Hormone made by glands in the small intestine that stimulates pancreatic secretion. The word "hormone" was coined by the English physiologists Wm. M. Bayliss and Ernest H. Starling in connection with their discovery of secretin, the first hormone, in 1902.
    Hormone, T3: Triiodothyronine, a thyroid hormone. The number 3 is usually in subscript.
    Hormone,T4: Thyroxine, a thyroid hormone. The number 4 is usually in subscript.
    Hormone therapy: A form of treatment that takes advantage of the fact that certain cancers depend on hormones to grow. The treatment may include giving hormones to the patient or decreasing the level of hormones in the body.
    Hormone, thyroid: Chemical substance made by the thyroid gland which is located in the front of the neck. The thyroid gland uses iodine to make thyroid hormones. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3).
    Hormone, thyroid stimulating (TSH): A hormone produced by the pituitary gland (at the base of the brain) that promotes the growth of the thyroid gland (in the neck) and stimulates it to produce its thyroid hormones. Normally, the rate of thyroid hormone production is controlled by the pituitary. When there are insufficient thyroid hormones in the body for normal functioning of the cells, the pituitary releases TSH. TSH in turn "stimulates" the thyroid gland to produce more thyroid hormones. In contrast, when there is excessive amount of thyroid hormones, the pituitary gland stops producing TSH. The TSH level then falls and thyroid hormone production is reduced. This mechanism maintains a relatively constant level of thyroid hormones circulating in the blood. This phenomenon is analogous to a thermostat used for temperature regulation in a room: when the temperature rises, the thermostat shuts the heater off and the room temperature falls back to normal. High levels of thyroid hormones cause the TSH level to fall, resulting in no further stimulation of the thyroid gland. In hyperthyroidism, there are continuously elevated levels of the thyroid hormones. TSH is also known as thyrotropin.
    Hormone, thyrotropin: A hormone produced by the pituitary gland (at the base of the brain) that promotes the growth of the thyroid gland (in the neck) and stimulates it. The suffix -tropin indicates "an affinity for". Thyrotropin has an affinity for the thyroid. Thyrotropin is known also as thyroid stimulating hormone (TSH).
    Hormone, thyroxine: A chemical substance made by the thyroid gland The thyroid gland uses iodine to make thyroid hormones. Thyroxine (T4), one of the most important thypoid hormones, has four iodine molecules attached to its molecular structure.
    Hormone, triiodothyronine: A hormone made by the thyroid gland. The thyroid gland uses iodine to make thyroid hormones. Triiodothyronine (T3) has three iodine molecules attached to its molecular structure. Iodine is found in seafood, bread, seaweed, and ordinary table salt.
    Hormone, TSH: Stands for Thyroid Stimulating Hormone. Also known as thyrotropin.
    Horner syndrome: A complex of abnormal findings, namely sinking in of one eyeball, ipsilateral ptosis (drooping of the upper eyelid on the same side) and miosis (constriction of the pupil of that eye) together with anhidosis (lack of sweating) and flushing of the affected side of the face. Due to paralysis of certain nerves (specifically, the cervical sympathetic nerves). Also called Horner-Bernard syndrome, Bernard syndrome, Bernard-Horner syndrome and Horner’s ptosis (but best known as Horner syndrome).
    Hornet stings: Stings from hornets and other large stinging insects such as bees, yellow jackets and wasps can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A’s" of insect allergy are Adrenaline, Avoidance and Allergist.)
    HPV: Human papilloma virus.
    Ht: Abbreviation for height (and also heart).
    HUGO: Human Genome Organization (the international organization concerned with human genome research).
    Human chorionic gonadotropin (hCG): A human hormone made by chorionic cells (in the fetal part of the placenta), hCG is directed at the gonads and stimulates them. hCG becomes detectable (by immunologic means) within days of fertilization and forms the foundation of the common pregnancy tests. The level of hCG in maternal serum also enters as one component in the "double" and the "triple" screens used during pregnancy to assign risks of Down syndrome and other fetal disorders.
    Human gene therapy: Insertion of normal DNA directly into cells to correct a genetic defect. The treatment of disease by replacing, altering, or supplementing a gene that is absent or abnormal that is responsible for the disease. In gene therapy for cancer, for example, researchers are trying to bolster the body’s natural capacity to combat cancer and make the tumor more sensitive to other kinds of therapy. Gene therapy, still in its early stages, holds great promise for the treatment of many diseases.
    Human immunodeficiency virus: See HIV.
    Human papilloma virus (HPV): A family of over 60 viruses responsible for causing warts. The majority of the viruses produce warts on the hands, fingers, and even the face. Most of these viruses are innocuous, causing nothing more than cosmetic concerns. Several types of HPV are confined primarily to the moist skin of the genitals, producing genital warts and elevating the risk for cancer of the cervix. The papilloma viruses that cause wartlike growths on the genitals are sexually transmitted.
    Humerus: The long bone in the upper arm which extends from the shoulder to the elbow.
    Humidifier: A machine that puts moisture in the air.
    Humor: In medicine, humor refers to a fluid (or semifluid) substance. Thus, the aqueous humor is the fluid normally present in the front and rear chambers of the eye.
    Humoral: Pertaining to elements in the blood or other body fluids.
    Human genome: The full collection of genes in a human being.
    Human Genome Project: International effort aimed at identifying and sequencing (ordering) all of the bases in the human genome. American participation in this monumental undertaking has been supported by funds from the National Institutes of Health (NIH) and the Department of Energy (DOE).
    Huntington's disease: An hereditary disorder with mental and physical deterioration leading to death. Although characterized as an "adult-onset" disease (as is usually the case), we have seen children with full-blown Huntington's disease.
    Hurler syndrome: A genetic error of metabolism. There is incomplete breakdown and accumulation of a substance (a mucopolysaccharide) which is abnormally stored in the brain and other places. This usually leads to death of the individual with Hurler syndrome by their early teen years. See gargoylism.
    Hybrid: The result of a cross between genetically unlike parents.
    Hybridoma: A cell hybrid resulting from the fusion of a cancer cell and a normal lymphocyte (a type of white blood cell). The hybridoma is immortal in the laboratory and makes the same products as its parent cells forever.
    Hydatid (hydatidiform) mole: An abnormal pregnancy without a placenta or embyro that eventuates in a mass of cysts resembling a bunch of grapes.
    Hydrocele: Accumulation of fluid in the coat around the testis. Small hydroceles tend to disappear by a year of age while larger hydroceles may persist and warrant surgery.
    Hydrocephalus: Abnormal buildup of cerebrospinal fluid in the ventricles of the brain. The fluid is often under increased pressure and can compress and damage the brain. Treatment is by insertion of a shunt to let the excess fluid exit and relieve the pressure.
    Hydrocephaly: See hydrocephalus.
    Hydronephrosis: Distention of the kidney with urine. Due to obstruction of urine outflow (for example, by a stone blocking the ureter, the tube going from the kidney to the bladder).
    Hymen: A thin membrane which completely or partially occludes the vaginal opening.
    Hyper-: Prefix meaning high, beyond, excessive, above normal. For example, hypercalcemia is high calcium in the blood.
    Hyperadrenocorticism: Excess hormone called "cortisol". Often called Cushing’s syndrome, it is an extremely complex condition that involves many areas of the body. It results from an excess of cortisol and its effects on the human body. Common symptoms are thinning of the skin, weakness, weight gain, bruising, hypertension, diabetes, weak bones (osteoporosis), facial puffiness, and in women cessation of periods. One of the commonest causes of Cushing’s syndrome is the administration of "cortisol-like medications" for the treatment of diverse diseases. All other cases of Cushing’s syndrome are due to excess production of cortisol by the adrenal gland including 1) an abnormal growth of the pituitary gland, which stimulates the adrenal gland, 2) a benign or malignant growth within the adrenal gland itself, which produces cortisol and 3) production within another part of the body (ectopic production) of a hormone that directly or indirectly stimulates the adrenal gland to make cortisol. Harvey Cushing (1869-1939), a neurosurgeon, described hyperadrenocorticism due specifically to an ACTH-secreting basophilic pituitary adenoma, a benign pituitary tumor that puts out ACTH (AdrenoCorticoTropic Hormone) that, in turn, drives (or overdrives) the adrenal gland.
    Hyperaldosteronism: Overproduction of the hormone aldosterone from the outer portion (cortex) of the adrenal gland or a tumor containing that type of tissue. Excess aldosterone (pronounced al-do-ster-one) results in low potassium levels (hypokalemia), underacidity of the body (alkalosis), muscle weakness, excess thirst (polydipsia), excess urination (polyuria), and high blood pressure (hypertension). Also called aldosteronism and Conn’s syndrome.
    Hyperbilirubinemia: An elevated level of the pigment bilirubin in the blood. A sufficient elevation will produce jaundice. Some degree of hyperbilirubinemia is very common in babies right after birth, especially premies.
    Hypercalcemia: A higher-than-normal level of calcium in the blood. This can cause a number of nonspecific symptoms, including loss of appetite, nausea, thirst, fatigue, muscle weakness, restlessness, and confusion. Excessive intake of calcium may cause muscle weakness and constipation, affect the conduction of electrical impulses in the heart (heart block) lead to calcium stones (nephrocalcinosis), in the urinary tract, impair kidney function, and interfere with the absorption of iron predisposing to iron deficiency. According to the National Academy of Sciences, adequate intake of calcium is 1 gram daily for both men and women. The upper limit for calcium intake is 2.5 grams daily.
    Hypercholesterolemia: High blood cholesterol. See familial hypercholesterolemia.
    Hyperglycemia: Elevated level of the sugar glucose in the blood.
    Hyperkalemia: Elevated blood potassium.
    Hyperlipidemia: High lipid (fat) levels in the blood.
    Hypermagnesemia: Excess magnesium. Persons with impaired kidney function should be especially careful about their magnesium intake because they can accumulate magnesium, a dangerous (and sometimes fatal) situation. According to the National Academy of Sciences, the Recommended Dietary Allowances of magnesium are 420 milligrams per day for men and 320 milligrams per day for women. The upper limit of magnesium as supplements is 350 milligrams daily, in addition to the magnesium from food and water. Too much magnesium is hypermagnesemia.
    Hypermobility syndrome: A common benign childhood condition involving hypermobile joints (that can move beyond the normal range of motion). Symptoms include pains in knees, fingers, hips, and elbows. The affected joints may sprain or dislocate. Scoliosis (curvature of the spine) is more frequent. Usually improves with adulthood. Also called the joint hypermobility syndrome.
    Hypernatremia: Elevated blood sodium.
    Hyperphosphatemia: A higher than normal blood level of phosphate. Phosphate molecules are particularly important as part of larger molecules in cell energy cycles. Higher than normal levels can be caused by ingestion of phosphate rich foods (diary products) or kidney failure.
    Hyperpigmented: Overly pigmented.
    Hyperplasia: A precancerous condition in which there is an increase in the number of normal cells lining the uterus.
    Hypertension: High blood pressure, defined as a repeatedly elevated blood pressure exceeding 140 over 90 mmHg. High blood pressure (hypertension) is "the silent killer." Chronic high blood pressure can stealthily cause blood vessel changes in the back of the eye (retina), abnormal thickening of the heart muscle, kidney failure, and brain damage. No specific cause for high blood pressure is found in 95% of patients. High blood pressure is treated with salt restriction, regular aerobic exercise, and medications.
    Hyperthermia: Treatment that involves heating a tumor.
    Hyperthyroid: Excess of thyroid hormone resulting from an overactive thyroid gland (or taking too much thyroid hormone).
    Hypertonia: Increased tone of skeletal muscles. Basically, too tight muscles.
    Hypertonic solution: One with more salt than in normal cells and blood.
    Hyperuricemia: Abnormally elevated blood level of uric acid. Uric acid is a breakdown product of purines that are part of many foods we eat. While hyperuricemia may indicate an increased risk of gout, the relationship between hyperuricemia and gout is unclear. Many patients with hyperuricemia do not develop gout, while some patients with repeated gout attacks have normal or low blood uric acid levels. Among the male population in the United States, approximately ten percent have hyperuricemia. However, only a small portion of those with hyperuricemia will actually develop gout.
    Hyperventilation: Overbreathing. Due to anxiety. Overbreathing causes dizziness, lightheadedness, a sense of unsteadiness and tingling around the mouth and fingertips. Relief can be gotten by breathing in and out of a paper bag (to increase the level of carbon dioxide). Opposite, hypoventilation or underbreathing.
    Hypo-: Prefix meaning low, under, beneath, down, below normal. For example, hypocalcemia is olow calcium in the blood.
    Hypocalcemia: Lower-than-normal blood calcium. Low blood calcium makes the nervous system highly irritable with tetany (spasms of the hands and feet, muscle cramps, abdominal cramps, overly active reflexes, etc.) Chronic calcium deficiency contributes to poor mineralization of bones, soft bones (osteomalacia) and osteoporosis; and, in children, rickets and impaired growth. Food sources of calcium include dairy foods, some leafy green vegetables such as broccoli and collards, canned salmon, clams, oysters, calcium-fortified foods, and tofu. According to the National Academy of Sciences, adequate intake of calcium is 1 gram daily for both men and women. The upper limit for calcium intake is 2.5 grams daily.
    Hypoglycemia: Low level of the sugar glucose in the blood.
    Hypokalemia: Low blood potassium.
    Hypomagnesemia: Too little magnesium. Magnesium deficiency can occur due to inadequate intake or impaired intestinal absorption of magnesium. Low magnesium (hypomagnesemia) is often associated with low calcium (hypocalcemia) and low potassium (hypokalemia). Deficiency of magnesium causes increased irritability of the nervous system with tetany (spasms of the hands and feet, muscular twitching and cramps, spasm of the larynx, etc.). According to the National Academy of Sciences, the Recommended Dietary Allowances of magnesium are 420 milligrams per day for men and 320 milligrams per day for women. The upper limit of magnesium as supplements is 350 milligrams daily, in addition to the magnesium from food and water.
    Hyponatremia: Low blood sodium.
    Hypoplasia of the thymus and parathyroids: Also known as the DiGeorge syndrome (DGS), this disorder is characterized by (1) low blood calcium levels (hypocalcemia) due to underdevelopment (hypoplasia) of the parathyroid glands needed to control calcium; (2) underdevelopment (hypoplasia) of the thymus, an organ behind the breastbone in which lymphocytes mature and multiply; and (3) defects of the outflow tracts from the heart. Most cases of DGS are due to a microdeletion in chromosome band 22q11.2. A small number of cases have defects in other chromosomes, notably 10p13. Named after the American pediatric endocrinologist Angelo DiGeorge. Another name for DGS is the third and fourth pharyngeal pouch syndrome (since the faulty structures in DGS are embryologically derived from the third and fourth pharyngeal pouches).
    Hypophosphatemia: A less than normal blood level of phosphate. The opposite of hyperphosphatemia.
    Hypopigmented: Underpigmented.
    Hypoplasia: Underdevelopment or incomplete development of a tissue or organ.For example, there can be hypoplasia (underdevelopment) of the enamel of the teeth. Hypoplasia is less drastic than aplasia where there is no development at all.
    Hypotension: Low (abnormally low) blood pressure. Hypotension is a consistent finding in shock but is also found in other conditions and so is not necessarily diagnostic of shock. The word hypotension is a hybrid of the Greek "hypo" meaning "under" and the Latin "tensio" meaning "to stretch." In French, "la tension" is "the blood pressure."
    Hypotension, orthostatic: Some symptoms of dizziness such as wooziness, feeling about to black out, and tunnel vision can be due to insufficient blood flow to the brain. The cause is transient low blood pressure (hypotension) due usually to suddenly standing up (orthostatic). The symptoms are typically worse when standing, improve with lying down and may be experienced by healthy individuals who rise quickly from a chair, often after a meal, and have a few seconds of disorientation.
    Hypothalamus: The area of the brain that controls body temperature, hunger, and thirst.
    Hypothermia: Abnormally low body temperature. Someone who falls asleep in a snowbank may become hypothermic. Hypothermia is intentionally produced to slow the metabolism during some types of surgery.
    Hypothyroid: Deficiency of thyroid hormone.
    Hypotonia: Decreased tone of skeletal muscles. In a word, floppiness.
    Hypotonic solution: One with less salt than in normal cells and blood.
    Hypovolemia: Abnormal decrease in blood volume (strictly speaking, in the blood plasma).
    Hypovolemic shock: See shock.
    Hypoxia: Concentration of oxygen in arterial blood that is less than normal. Anoxia refers to complete lack of oxygen.
    Hypoxia-ischemia: See hypoxia. Ischemia refers to blood flow to cells and organs that is not sufficient to maintain their normal function.
    Hypoxic-ischemic encephalopathy: Damage to cells in the central nervous system (the brain and spinal cord) from inadequate oxygen. Hypoxic-ischemic encephalopathy allegedly may cause in death in the newborn period or result in what is later recognized as developmental delay, mental retardation, or cerebral palsy. This is an area of considerable medical and medicolegal debate.
    Hysterectomy: An operation to remove the uterus and sometimes also the cervix.
    Hysterectomy, abdominal: Surgical removal of the uterus through an incision made in the abdominal wall. As opposed to a vaginal hysterectomy.
    Hysterectomy, complete: Complete surgical removal of the uterus and cervix. Also called a total hysterectomy.
    Hysterectomy, partial: The uterus is sugically removed but the cervix is left is left in place. Also called a subtotal hysterectomy.
    Hysterectomy, subtotal: The uterus is surgically removed but the cervix is left is left in place. Also called a partial hysterectomy.
    Hysterectomy, total: Complete surgical removal of the uterus and cervix. Also called a complete hysterectomy.

    Hysterectomy, vaginal: Removal of the uterus through a surgical incision, not of the abdomen but, within the vagina. With a vaginal hysterectomy, the scar is not outwardly visible. A vaginal hysterectomy is in contrast to an abdominal hysterectomy.
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    Iatr(o)-: Prefix relating to a physician or medicine. From the Greek word "iatros" meaning physician (healer).
    Iatrapistic: A lack of faith in doctors. Entirely from the Greek: "iatr-" indicating a relationship to a physician or medicine + "a" meaning lack + "pisteuo" meaning I trust in.
    -iatrics: Suffix meaning healing. From the Greek "iatros" meaning healer or physician. Pediatrics is the healing of children. And geriatrics is the healing (or at least the treatment) of disorders characteristic of the aged.
    Iatrogenic: Due to the activity of a physician or therapy. From the Greek "iatros" meaning physician + "gennao" meaning I produce. Iatrogenic is defined by Merriam-Webster's Collegiate Dictionary as: "induced inadvertently by a physician or surgeon or by medical treatment or diagnostic procedures." For example, an iatrogenic illness is one caused by a medicine or doctor.
    Iatromelia: Ineffective or negligent medical treatment. From "iatro-" meaning a relationship to a physician or medicine + the Greek "meleos" meaning fruitless or vain.
    Iatromisia: An intense dislike of doctors. From "iatro-" indicating a relationship to a physician or medicine + the Greek "miseo" meaning I hate.
    -iatry: Suffix meaning medical treatment. From the Greek "iatreia" meaning healing, which came from "iatros" meaning treatment (or physician). Psychiatry is literally the medical treatment of the psyche.
    Icterus: Jaundice.
    ICU: Intensive Care Unit.
    IgE: Immunoglobulin E. The E stands for erythema or redness. See Immunoglobulin E.
    IL-2: Abbreviation for interleukin-2.
    Ileitis: Inflammation of the ileus.
    Ileus: Part of the small intestine beyond the jejunum and before the large intestine (colon).
    Ileitis, terminal: Crohn’s disease, a chronic inflammatory disease of the intestine involving only the end of the small intestine (the terminal ileum). Crohn’s disease affects primarily the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease often strikes persons in their teens or early twenties. It tends to be chronic, recurrent with periods of remission and exacerbation. In the early stages. It causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery.
    Ileocolitis, Crohn’s: Crohn’s disease involving both the ileum (the furtherest part of the small intestine just before the colon) and the large intestine (the colon). Crohn’s disease is a chronic inflammatory condition of the intestine primarily involving the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition with periods of remission and exacerbation. In the early stages, Crohn’s disease causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs. When only the large intestine (colon) is involved, the condition is called Crohn’s colitis. When only the small intestine is involved, the condition is called Crohn’s enteritis. When only the end of the small intestine (the terminal ileum) is involved, it is termed terminal ileitis. Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery.
    Iliac: Pertaining to the ilium.
    Iliac horns: Symmetrical bilateral central posterior iliac processes. In other words, horn-like malformations of the crest of both iliac bones of the pelvis. A characteristic finding in the nail-patella syndrome.
    Ilium: Upper part of the pelvis which forms the receptacle of the hip.
    Idiopathic: The cause is unknown.
    IM: Intramuscular. An IM medication is given by needle into the muscle.
    Immune: Protected against infection. The Latin immunis means free, exempt.
    Immune response: Any reponse by the immune system.
    Immune system: A complex system that is responsible for distinguishing us from everything foreign to us and for protecting us against infections and foreign substances.
    Immunity: The condition of being immune. Immunity can be innate (for example,humans are innately immune to canine distemper) or conferred by a previous infection or immunization.
    Immunization: Immunizations, or vaccinations, work by stimulating the immune system, the natural disease-fighting system of the body. The healthy immune system is able to recognize invading bacteria and viruses and produce substances (antibodies) to destroy or disable them. Immunizations prepare the immune system to ward off a disease. To immunize against viral diseases, the virus used in the vaccine has been weakened or killed. To immunize against bacterial diseases, it is generally possible to use only a small portion of the dead bacteria to stimulate the formation of antibodies against the whole bacteria. In addition to the initial immunization process, it has been found that the effectiveness of immunizations can be improved by periodic repeat injections or "boosters." Also see Immunizations (in the plural) and Immunization of a specific type (such Immunization, Polio).
    Immunization, anthrax: A series of six shots over six months and booster shots annually, the anthrax vaccine now in use in the USA was first developed in the 1950s and approved by the Food and Drug Administration for general use in 1970. It is produced by the Michigan Biologic Products Institute of Michigan’s Department of Health and is given routinely to veterinarians and others working with livestock. In December, 1997 it was announced that all US military would receive the vaccine, as do the military in the UK and Russia, the reason being concern that anthrax might be used in biologic warfare.
    Immunization, children’s: In the United States, it is recommended that all children receive vaccination against:
    Hepatitis B 
    Diphtheria, tetanus, pertussis 
    Haemophilus influenzae type B (HIB) 
    Poliovirus 
    Measles, mumps, rubella 
    Varicella zoster virus (chickenpox). 
    Every child in the U.S. should have these vaccinations except when there are special circumstances and the child’s doctor advises specifically against a vaccination. 
    Immunization, chickenpox: This vaccine prevents the common disease known as chickenpox (varicella zoster). While chickenpox is often considered a trivial illness, it can cause significant lost time on the job and in school and have serious complications including ear infections, pneumonia, and infection of the rash with bacteria, inflammation of the brain (encephalitis) leading to difficulty with balance and coordination (cerebellar ataxia), damaged nerves (palsies), and Reye’s syndrome, a potentially fatal complication. The vaccination requires only one shot given at about a year of age. If an older person has not had chickenpox, the shot may be given at any time. There have been few significant reactions to the chickenpox vaccine. All children, except those with a compromised immune system, should have the vaccination.
    Immunization, DPT: DPT immunization protects from diphtheria, pertussis (whooping cough), and tetanus and is given in a series of 5 shots at 2, 4, 6, 18 months of age and 4-6 years of age. Thanks to vaccination programs, these diseases have become less common. However, there are still unvaccinated individuals capable of carrying and passing diphtheria and pertussis to others who are not vaccinated. Tetanus bacteria are prevalent in natural surroundings, such as contaminated soil. See also Immunization, DTaP.
    Immunization, DTaP: Like DPT, DTaP protects from diphtheria, pertussis (whooping cough) and tetanus. DTaP is the same as DTP, except that it contains only acellular pertussis vaccine which is thought to cause fewer of the minor reactions associated with immunization and is also probably less likely to cause the more severe reactions occasionally seen following pertussis vaccination. DTaP is currently recommended only for the shots given at 18 months and 4-6 years of age.
    Immunization, DT: DT (diphtheria and tetanus) vaccine does not protect from pertussis and is usually reserved for individuals who have had a significant adverse reaction to a DPT shot or who have a personal or family history of a seizure disorder or brain disease.
    Immunization, flu: The flu (influenza) vaccine is recommended for persons at high risk for serious complications from influenza infection, including everyone 65 or over; people with chronic diseases of the heart, lung or kidneys, diabetes, immunosuppression, or severe forms of anemia; residents of nursing homes and other chronic-care facilities, children and teenagers taking aspirin therapy (and who may therefore be at risk for developing Reye syndrome after an influenza infection), and those in close or frequent contact with anyone at high risk. Persons with an allergy to eggs should not receive influenza vaccine.
    Immunization, German measles: See Immunization, MMR.
    Immunization, Haemophilus influenzae type B: See Immunization, HIB.
    Immunization, hepatitis A: When immediate protection against hepatitis A (infectious hepatitis) is needed, immunoglobulins are used. Protection is effective only if given within 2 weeks of exposure and lasts but 2-4 months. Immunoglobulins can be used to protect household contacts of someone with acute viral hepatitis and travelers to regions with poor sanitation and high hepatitis A rates, when the traveler has to depart sooner than the vaccines can take effect (about 2 weeks). Travelers can receive the immunoglobulin and vaccine simultaneously and be protected immediately and for longer term. When immediate protection is not needed, hepatitis A vaccines are considered for individuals in high-risk settings, including frequent world travelers, sexually active individuals with multiple partners, homosexual men, individuals using illicit drugs, employees of daycare centers, and certain health care workers, and sewage workers. Two hepatitis A vaccines called HAVRIX and VAQTA are commercially available in the U.S. Both are highly effective and provide protection even after only one dose. Two doses are recommended for adults and 3 doses for children (under 18 years of age) to provide prolonged protection.
    Immunization, hepatitis B: Hepatits B (hep B) vaccine gives prolonged protection, but 3 shots over a half year are usually required. In the U.S., all infants receive hep B vaccine. Two vaccines (ENGERIX-B, and RECOMBIVAX-HB) are available in the US. The first dose of hep B vaccine is frequently given while the newborn is in the hospital or at the first doctor visit following birth. The second dose is given about 30 days after the initial dose. A booster dose is performed approximately six months later. Babies born to mothers testing positive for hep B receive, in addition, HBIG (hep B immune globulin) for prompt protection. Older children (11-12 years) are advised to receive a hep B booster as are adults in high-risk situations including healthcare workers, dentists, intimate and household contacts of patients with chronic hep B infection, male homosexuals, individuals with multiple sexual partners, dialysis patients, IV drug users, and recipients of repeated transfusions. Health care workers accidentally exposed to materials infected with hep B (such as needle sticks), and individuals with known sexual contact with hep B patients are usually given both HBIG and vaccine to provide immediate and long term protection.
    Immunization, H. flu: See Immunization, HIB.
    Immunization, HIB: This vaccine is to prevent disease caused by the Haemophilus influenzae type B (HIB) bacteria. The H. influenzae (H. flu) bacteria can cause a range of serious diseases including meningitis with potential brain damage and epiglottitis with airway obstruction poisoning. The HIB vaccine is usually given at 2, 4 and 6 months of age. A final booster is given at 12-15 months of age. HIB vaccine rarely causes severe reactions.
    Immunization, infectious hepatitis: See Immunization, hepatitis A.
    Immunization, influenza: See Immunization, flu.
    Immunization, measles: See Immunization, MMR.
    Immunization, MMR: The standard vaccine given to prevent measles, mumps and rubella (German measles). The MMR vaccine is now given in two dosages. The first should be given at12-15 months of age. The second vaccination should be given at 4-6 years (or, alternatively, 11-12 years) of age. Most U.S. colleges require proof of a second measles or MMR vaccination prior to entrance. Most children should receive MMR vaccinations. Exceptions may include children born with an inability to fight off infection, some children with cancer, on treatment with radiation or drugs for cancer, on long term steroids (cortisone). People with severe allergic reactions to eggs or the drug neomycin should probably avoid the MMR vaccine. Pregnant women should wait until after delivery before being immunized with MMR. People with HIV or AIDS should normally receive MMR vaccine. Measles, mumps, and rubella vaccines may be administered as individual shots, if necessary, or as a measles-rubella combination.
    Immunization, mumps: See Immunization, MMR.
    Immunization, pneumococcal pneumonia: This vaccine, which prevents one of the most common and severe forms of pneumonia, is usually given only once in a lifetime, usually after the age of 55, to someone with ongoing lung problems (such as chronic obstructive pulmonary disease (COPD) or asthma) or other chronic diseases (including those involving the heart and kidneys). This vaccination would rarely be given to children.
    Immunization, polio: The vaccines available for vaccination against polio are OPV (Oral Polio Vaccine) and IPV (Inactivated Polio Vaccine). OPV is still the preferred vaccine for most children. As its name suggests, it is given by mouth. IPV, or Inactivated Polio Vaccine is given as a shot in the arm or leg. Infants and children should be given four doses of OPV. The doses are given at 2 months, 4 months, 6-18 months and 4-6 years of age. Persons allergic to eggs or the drugs neomycin or streptomycin should receive OPV, not the injectable IPV. Conversely, IPV should be given If the vaccine recipient is on long-term steroid (cortisone) therapy, has cancer, or is on chemotherapy or if a household member has AIDS or there is an unimmunized adult in the house.
    Immunization, rubella: See Immunization, MMR.
    Immunization, serum hepatitis: See Immunization, hepatitis B.
    Immunization, Td: Td is the vaccine given to children over six and adults as boosters for immunity to diphtheria and tetanus.
    Immunization, varicella zoster: See Immunization, chickenpox.
    Immunocompetant: Able to develop an immune response. The opposite of immunodeficient.
    Immunodeficiency: Inabillity to mount a normal immune response. Immunodeficiency can be due to a genetic disease or acquired as in AIDS due to HIV.
    Immunodeficient: Lacking immunity and so susceptible to infection.
    Immunodepression: See immunosuppression.
    Immunogenetics: The genetics (inheritance) of the immune response. For example, the study of the Rh, ABO and other blood groups or the HLA system important to kidney and other transplants.
    Immunoglobulin E (IgE): Antibody of a specific class used to fight invading allergic substances (allergens). An allergic person frequently has elevated blood levels of IgE. IgE antibodies attack and engage the invading army of allergens.
    Immunologist: A person who is knowledgeable about immunology.
    Immunology: The study of all aspects of the immune system including its structure and function, disorders of the immune system, blood banking, immunization and organ transplantation.
    Immunosuppression: Lowering the immune response, for example, with radiation or medications.
    Immunotherapy, allergy: Stimulation of the immune system with gradually increasing doses of the substances to which a person is allergic, the aim being to modify or stop the allergy "war" (by reducing the strength of the IgE and its effect on the mast cells). This form of treatment is very effective for allergies to pollen, mites, cats, and especially stinging insects (eg, bees, hornets, yellow jackets, wasps, velvet ants, fire ants). Allergy immunotherapy usually takes 6 months to a year to become effective and "shots" (injections) are usually required for 3-5 years.
    Impact: To lodge firmly or wedge in.
    Impaction, dental: Teeth pressing together. For example, molar teeth (the large teeth in the back of the jaw) can be impacted, cause pain and require pain medication, antibiotics, and surgical removal.
    Impotence: An inability to sustain an erection sufficient for sexual intercourse or to achieve ejaculation, or both. Impotence usually has a physical cause, such as disease, injury, drug side-effects, or a disorder that impairs blood flow in the penis. Impotence can also have an emotional cause. Impotence is treatable in all age groups.
    Imperforate anus: Birth defect where the rectum is a blind alley and there is no anus.
    Impetigo: A strep(tococcal) skin infection.
    Imprinting: A remarkable genetic phenomenon. The gist is that gene expression depends on the sex of the transmitting parent. There is, for example, increased severity of neurofibromatosis when the gene for it came from the mother.
    in: Abbreviation for inch.
    Inborn errors of metabolism: Term coined by A. Garrod in 1908 applying to heritable disorders of biochemistry. Examples include albinism, cystinuria (a cause of kidney stones) and phenylketonuria (PKU) are a few of the hundreds of inborn errors of metabolism.
    Inbreeding: The mating of two closely related persons. Also called consanguinity.
    Inbreeding, coefficient of: A statistical way of gauging how close two people are as to their genes. The coefficient of inbreeding (symbolized as F) is the probability that a person with two identical genes received both genes from an identical ancestor. Take, for example, first cousins. They share a set of grandparents. For any particular allele (gene) in the father, the chance that the mother inherited the same allele from the same source is 1/8. For any gene the father passes to his child, the chance is 1/8 that the mother has the same gene and ½ that she transmits that gene to the child so 1/8 X ½ = 1/16. Thus, a first-cousin marriage has a coefficient of inbreeding F =1/16. The added risks to the offspring of first cousins depend not only upon this coefficient of inbreeding but also upon the genetic family history and, in some cases, upon test results (as to beta thalassemia, for instance, for first cousins of Italian descent). There are always added risks from the mating of closely related persons.
    Incest: Sexual activity between individuals so closely related that marriage is prohibited. Incest involving a child is a form of child abuse.
    Inch: In length, 1/12th of foot or 1/36 of a yard or, metrically, 2.54 centimeters. The inch, along with the foot and yard, are Old World creations to which the USA has stubbornly clung. The inch was originally about the length of the last bone (distal phalanx) in a man’s thumb and served as a measurement of land. The etymology (word history) of "inch" is remarkable. It originally meant "one twelfth". The abbreviation is "in."
    Incision: A cut. When making an incision, a surgeon is making a cut.
    Incontinence: Inability to control excretions. Urinary incontinence is inability to keep urine in the bladder. Fecal incontinence is inability to retain feces in the rectum.
    Incontinence, fecal: Inability to hold feces in the rectum. This is due to failure of voluntary control over the anal sphincters permitting untimely passage of feces and gas. Also called rectal incontinence.
    Incontinence of urine: Inability to hold urine in the bladder. This is due to failure of voluntary control over the urinary sphincters resulting in involuntary passage of urine (wetting).
    Incontinence, rectal: Inability to hold feces in the rectum due to failure of voluntary control over the anal sphincters with involuntary passage of feces and gas. Also called fecal incontinence.
    Incontinence, urinary: Inability to hold urine in the bladder. This is due to failure of voluntary control over the urinary sphincters resulting in involuntary passage of urine (wetting).
    Incontinent: Unable to control excretions, to hold urine in the bladder or keep feces in the rectum. (This is the usual medical meaning of the word incontinent, not continent. Incontinent can also refer to a lack of self-restraint in the sexual arena, failure to refrain from sexual intercourse.)
    Incontinentia pigmenti (IP): A genetic disease with blisters that develop soon after birth on the trunk and limbs, then heal, but leave dark (hyperpigmented) streaks and marble-like whorls on the skin. (The name came from the erroneous idea that the skin cells were incontinent of pigment and could not contain it normally.) Other key features of IP include dental and nail abnormalities, bald patches, and (in about 1/3rd of cases) mental retardation. IP is an X-linked dominant with male lethality. The IP gene is in band q28 on the X chromosome. Mothers with IP have an equal chance of having a normal or IP daughter or a normal son. The IP sons die before birth. IP is also known as Bloch-Sulzberger syndrome.
    Index case: A person who first draws attention to their family. For example, if my eye doctor discovers I have glaucoma and subsequently other cases of glaucoma are found in my family, I am the index case. Also called the propositus (if male) or proposita (if female).
    Infant: The child up to 24 months of age. The word infant is from the Latin meaning not speaking.
    Infant mortality rate: The number of children dying under a year of age divided by the number of live births that year. The infant mortality rate in the United States, which was 12.5 per 1,000 live births in 1980, fell to 9.2 per 1,000 live births in 1990.
    Infantile paralysis: Old synonym for polio.
    Infarct: An area of tissue death due to a local lack of oxygen.
    Infarction: Formation of an infarct. Also means the same as an infarct.
    Infection, urinary tract (UTI): An infection in the urinary system that begins when microorganisms cling to the opening of the urethra (the canal from the bladder) and begin to multiply. Most UTIs are due to one type of bacteria, E. (Escherichia) coli, a normal denizen of the colon. An infection in the urethra leads to inflammation called urethritis. From there bacteria may move up, causing a bladder infection (cystitis) and if the infection is not treated promptly, bacteria may go up the ureters to infect the kidneys (pyelonephritis). Factors leading to UTI include any abnormality of the urinary tract (such as a urinary tract malformation or a kidney stone) that obstructs the flow of urine, an enlarged prostate gland that slows the flow of urine, catheters (tubes) in the bladder, diabetes (due to changes of the immune system), and any disorder that suppresses the immune system. Women have more UTI than men, probably because a woman’s urethra is shorter (allowing bacteria quick access to the bladder) and nearer sources of bacteria from the anus and vagina. For many women, sexual intercourse seems to trigger an infection, as may the use of a diaphragm. Not everyone with a UTI has symptoms but symptoms commonly include a frequent urge to urinate and a painful, burning when urinating (dysuria). The urine may look milky or cloudy, even reddish if blood is present. Kidney infection can cause pain in the back or side below the ribs. In children, symptoms may be easily missed or misunderstood. A child with a UTI may be irritable, not eat normally, have an unexplained fever, have incontinence or loose bowels, or just not thrive.
    Infectious hepatitis: See Hepatitis A.
    Infectious hepatitis immunization: See Immunization, hepatitis A.
    Infectious mono: See infectious mononucleosis.
    Infectious mononucleosis: A specific viral infection (with the Epstein-Barr virus) in which there is an increase of white blood cells that are mononuclear (with a single nucleus)"Mono" and "kissing disease" are popular terms for this very common illness caused by the Epstein-Barr virus (EBV). By the time most people reach adulthood, an antibody against EBV can be detected in their blood meaning they have been infected with EBV. The illness is less severe in young children. The infection can be spread by saliva. The incubation period for "mono" is 4 to 8 weeks. Symptoms include fever, fatigue, sore throat, and swollen lymph glands. "Mono" can cause liver inflammation (hepatitis) and spleen enlargement. Vigorous contact sports should be avoided to prevent spleen rupture.
    Inferior: In medicine, inferior means below or downward. The opposite of superior.
    Infertility: Diminished or absent ability to conceive and bear offspring (fertility).
    Infiltrate: To penetrate. If an IV infiltrates, the IV fluid penetrates the surrounding tissue.
    Inflammation: Inflammation is localized redness, warmth, swelling and pain as a result of infection, irritation or injury.
    Influenza: The flu is caused by viruses that infect the respiratory tract which are divided into three types, designated A, B, and C. Most people who get the flu recover completely in 1 to 2 weeks, but some people develop serious and potentially life-threatening medical complications, such as pneumonia. Much of the illness and death caused by influenza can be prevented by annual influenza vaccination.
    Influenza vaccine: The flu (influenza) vaccine is recommended for persons at high risk for serious complications from influenza infection, including everyone age 65 or more; people with chronic diseases of the heart, lung or kidneys, diabetes, immunosuppression, or severe forms of anemia; residents of nursing homes and other chronic-care facilities, children and teenagers receiving long-term aspirin therapy (and who may therefore be at risk for developing Reye syndrome after an influenza virus infection), people in close or frequent contact with anyone at high risk. People with an allergy to eggs should not receive influenza vaccine.
    Informatics: The application of computers and statistics to the management of information. For example, in the Human Genome Project, informatics includes the development and use of methods to search databases quickly, analyze DNA sequence information, and predict protein sequence and structure from DNA sequence data.
    Inguinal: Having to do with the groin.
    Inguinal canal: A passage in the lower anterior abdominal wall which in the male allows passage of the spermatic cord and in the female contains the round ligament. Because of the weakness it creates in the abdominal wall, it is the most frequent site for a hernia.
    Inguinal orchiectomy: Surgery to remove the testicle through the groin.
    Insect stings: Stings from large stinging insects such as bees, hornets, yellow jackets and wasps can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A’s" of insect allergy are Adrenaline, Avoidance and Allergist.)
    Insertion: Chromosome abnormality due to insertion of a segment from one chromosome into another chromosome.
    In situ hybridization: The use of a DNA or RNA probe to detect the complementary DNA sequence.
    Insulin: A hormone made by the islet cells of the pancreas. Insulin controls the amount of sugar in the blood.
    Interatrial septum: The partition separating the upper chambers (the atria) of the heart.
    Intercostal muscle: Muscle tissue between two ribs. This muscle is a type called skeletal muscle.
    Interferon: A substance used in biological therapy. Interferon helps the immune system slow the rate of growth and division of cancer cells, causing them to become sluggish and die. There are a number of interferons. All are proteins (lymphokines) produced by the body in response to infection. these substances interfere with cell infection. There are 3 main classes of interferon, alpha, beta, and gamma. The interferons have been synthesized using recombinant DNA technology.
    Interleukins: Substances used in biological therapy. Interleukins stimulate the growth and activities of certain kinds of white blood cells.
    Interleukin-2: A type of interleukin, a chemical messenger, a substance that can improve the body’s response to disease. It stimulates the growth of certain disease-fighting blood cells in the immune system. Also called IL-2.
    Internal medicine: A medical specialty dedicated to the diagnosis and medical treatment of adults. A physician who specializes in internal medicine is referred to as an internist. A minimum of seven years of medical school and postgraduate training are focused on learning the prevention, diagnosis, and treatment of diseases of adults. Subspecialties of internal medicine include allergy and immunology, cardiology (heart), endocrinology (hormone disorders), hematology (blood disorders), infectious diseases, gastroenterology (diseases of the gut), nephrology (kidney diseases), oncology (cancer), pulmonology (lung disorders), and rheumatology (arthritis and musculoskeletal disorders).
    Internal radiation therapy: Radiation therapy in which radioactive material is placed in or near a tumor.
    Internist: A physician who specializes in the diagnosis and medical treatment of adults. This specialty, called internal medicine, is dedicated to adult medicine. A minimum of seven years of medical school and postgraduate training are focused on learning the prevention, diagnosis, and treatment of diseases of adults. Subspecialties of internal medicine include allergy and immunology, cardiology (heart), endocrinology (hormone disorders), hematology (blood disorders), infectious diseases, gastroenterology (diseases of the gut), nephrology (kidney diseases), oncology (cancer), pulmonology (lung disorders), and rheumatology (arthritis and musculoskeletal disorders).
    Interphase: The interval in the cell cycle between two cell divisions when the individual chromosomes cannot be distinguished, interphase was once thought to be in resting phase but it is far from a time of rest for the cell. It is the time when DNA is replicated in the cell nucleus.
    Interstitial cystitis (IC): Disease that involves inflammation or irritation of the bladder wall. This inflammation can lead to scarring and stiffening of the bladder, and even ulcerations and bleeding. Diagnosis is based on symptoms, findings on cystoscopy and biopsy, and eliminating other treatable causes such as infection. Because doctors do not know what causes IC, treatments are aimed at relieving symptoms. Most people are helped for variable periods of time by one or a combination of treatments.
    Interstitial radiation: Radiation therapy in which a radioactive material is placed directly into a tumor.
    Intervening sequence: See intron.
    Interventricular septum: The stout wall separating the lower chambers (the ventricles) of the heart fromone another. A hole in the interventricular septum is termed a ventricular septal defect (VSD).
    Intestinal obstruction: Blockage of the intestine.
    Intestine: The long, tubelike organ in the abdomen that completes the process of digestion. It consists of the small and large intestines.
    Intestinal gas: The complaint referred to as "intestinal gas" is a common one and the discomfort can be quite significant. Everyone has gas and eliminates it by burping or passing it through the rectum. In many instances people think they have too much gas when in reality they have normal amounts. Most people produce 1 to 3 pints of intestinal gas in 24 hours and pass gas an average of 14 times a day. It is made up primarily of odorless vapors such as carbon dioxide, oxygen, nitrogen, hydrogen, and in some families, methane. The unpleasant odor is due to bacteria in the large intestine that release small amounts of gases containing sulfur.
    Intracranial: Inside the skull (the cranium). Intracranial hemorrhage A bleed inside the head.
    Intractable: Unstoppable. For example, intractable diarrhea or intractable pain.
    Intradermal: In the skin. An intradermal injection is given into the skin.
    Intraepithelial: Within the layer of cells that forms the surface or lining of an organ.
    Intrahepatic: Within the liver.
    Intramuscular: See IM.
    Intraocular: In the eye. The intraocular pressure is the pressure within the eye.
    Intraoperative radiation therapy: Radiation treatment given during surgery. Also called IORT.
    Intraperitoneal: Within the peritoneal cavity, the area that contains the abdominal organs.
    Intraperitoneal chemotherapy: Treatment in which anticancer drugs are put directly into the abdomen through a thin tube.
    Intrathecal chemotherapy: Treatment with drugs that are injected into the fluid surrounding the brain and spinal cort (cerebrospinal fluid).
    Intrauterine contraceptive device (IUD): A device inserted into the uterus (womb) to prevent conception (pregnancy). The IUD can be a coil, loop, triangle, or T-shape. It can be plastic or metal.
    Intravenous: Injected into a vein. Also called IV.
    Intravenous pyelogram: An x-ray of the kidneys and urinary tract. Structures are made visible by the injection of a substance that blocks x-rays. Also called IVP.
    Intrauterine: In the uterus (the womb).
    Intraventricular: In the ventricle of the heart or brain.
    Intron: Part of a gene that is initially transcribed into the primary RNA transcript but then removed from it when the exxon sequences on either side of it are spliced together. Also called an intervening sequence.
    Intubate: To put a tube in.
    Intussusception: A segment of intestine is prolapsed (telescoped) within another, which may lead to intestinal obstruction.
    Invasive cervical cancer: Cancer that has spread from the surface of the cervix to tissue deeper in the cervix or to other parts of the body.
    Inversion: A chromosome segment is clipped out, turned upside down and reinserted.
    In situ: In the normal location. An in situ tumor is one that is confined to its site of origin and has not invaded neighboring tissue or metastasized elsewhere.
    Invest: In medicine, this has nothing to do with the stock market. It means to envelop, cover, or embed.
    In vitro: The opposite of in vivo, it literally means in glass, that is in a test tube, in the laboratory. An in vitro test is one done in the lab, not in a living organism.
    In vivo: In the living organism.
    Involution: A retrograde change. After treatment, a tumor may involute. With advancing age, there may be physical and emotional involution.
    Iodide: The form to which iodine in the diet is reduced before it is absorbed through the intestinal wall into bloodstream and carried to the thyroid gland. See Iodine.
    Iodide goiter: See Iodine excess.
    Iodine: Essential element in the diet. The thyroid gland uses iodine to make thyroid hormones. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3). Thyroxine (T4) has four iodine molecules attached to its structure, while triiodothyronine (T3) has three iodine molecules attached. Iodine is found in seafood, bread, salt, and seaweed.
    Iodine deficiency: Iodine is a natural requirement of our diets. Iodine deficiency can lead to inadequate production of thyroid hormone from the thyroid gland (hypothyroidism). For example, in some parts of Zaire, Ecuador, India, and Chile, remote, mountainous areas, such as in the Alps (in the past), Andes and the Himalayas have a particular predisposition to severe iodine deficiency, goiter, and hypothyroidism. Since the addition of iodine to table salt, iodine deficiency is rarely seen in the United States.
    Iodine excess: Just as too little iodine can cause thyroid disease, so may prolonged intake of too much iodine also lead to the development of goiter (swelling of the thyroid gland) and hypothyroidism (abnormally low thyroid activity). Certain foods and medications contain large amounts of iodine. Examples include seaweed; iodine-rich expectorants (such as SSKI and Lugol’s solution) used in the treatment of cough, asthma, chronic pulmonary disease; and amiodarone (CARDORONE), an iodine-rich medication used in the control of abnormal heart rhythms (cardiac arrhythmias).
    Ipsilateral: On the same side. The opposite of contralateral (the other or opposite side). For example, a tumor involving the right side of the brain may affect vision ipsilaterally (that is, in the right eye).
    IPV: Inactivated Polio Vaccine. The polio virus in IPV has been inactivated (killed). Also called the Salk vaccine (after the American physician-virologist Jonas Salk). See Immunization, polio.
    Iridectomy: Making a hole in the iris.
    Iris: The circular, colored curtain of the eye. Its opening forms the pupil.
    Iritis: Inflammation of the iris. The iris is the circular, colored curtain in the front of the visible of the eye. (The opening of the iris forms the pupil.)
    Iron: An essential mineral. Iron is necessary for the transport of oxygen (via hemoglobin in red blood cells) and for oxidation by cells (via cytochrome). Deficiency of iron is a common cause of anemia. Food sources of iron include meat, poultry, eggs, vegetables and cereals (especially those fortified with iron). According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men. Iron overload can damage the heart, liver, gonads and other organs. Iron overload is a particular risk in people who may have certain genetic conditions (hemochromatosis) sometimes without knowing it and also in people receiving recurrent blood transfusions. Iron supplements meant for adults (such as pregnant women) are a major cause of poisoning in children.
    Iron deficiency: Deficiency of iron results in anemia because iron is necessary to make hemoglobin, the key molecule in red blood cells responsible for the transport of oxygen. In iron deficiency anemia, the red cells are unusally small (microcytic) and pale (hypochromic). Characteristic features of iron deficiency anemia in children include failure to thrive (grow) and increased infections. The treatment of iron deficiency anemia , whether it be in children or adults, is with iron and iron-containing foods. Food sources of iron include meat, poultry, eggs, vegetables and cereals (especially those fortified with iron). According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men.
    Iron excess:Iron overload can damage the heart, liver, gonads and other organs. Iron overload is a particular risk in people who may have certain genetic conditions (hemochromatosis) sometimes without knowing it and also in people receiving recurrent blood transfusions. According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men.
    Iron poisoning: Iron supplements meant for adults (such as pregnant women) are a major cause of poisoning in children. Care should be taken to keep iron supplements safely away from children.
    Irrigate: To wash out as, for example, a wound to clean it.
    Irritable bowel syndrome (IBS): A common gastrointestinal disorder, also called spastic colitis, mucus colitis or nervous colon syndrome, IBS is an abnormal condition of gut contractions (motility) characterized by abdominal pain, bloating, mucous in stools, and irregular bowel habits with alternating diarrhea and constipation, symtoms that tend to be chronic and wax and wane over the years. Although IBS can cause chronic recurrent discomfort, it does not lead to any serious organ problems. Diagnosis usually involves excluding other illnesses. Treatment is directed toward relief of symptoms and includes high fiber diet, exercise, relaxation techniques, avoidance of caffeine, milk products and sweeteners, and medications.
    Ischemia: Inadequate blood supply (circulation) to a local area due to blockage of the blood vessels to the area.
    Ischium: Bone making up the lower down back part of the pelvis.
    Islets of Langerhans: Insulin-producing tissue in the pancreas.
    Isochromosome: An abnormal chromosome with two identical arms due to duplication of one arm and loss of the other arm. (Found in some girls with Turner syndrome and in tumors.)
    Isodisomy: Remarkable situation where both chromosomes in a pair are from one parent and neither from the other. Isodisomy causes some birth defects and, we suspect, plays a role in cancer. Also called uniparental disomy.
    Isolate: A group in which mating is always between members of the group. For example, the Amish.
    Isotonic solution: One that has the same salt concentration as cells and blood.
    Isotope: A form of a chemical element with a different atomic mass. Isotopes are used in a number of medical tests.
    Itching: Medically known as pruritis. Something that is itchy is pruritic.
    itis: Word ending (suffix) meaning inflammation. For example, colitis is literally colon inflammation or figuratively inflammation of the colon. The ending -itis is one of the building blocks derived from Greek (in this case) or Latin used to construct medical terms.
    ITP: Idiopathic thrombocytopenic purpura.

    IUD: Intrauterine contraceptive device.
    IV: Inside a vein (blood vessel). Also called intravenous.

  • Jacksonian seizure: Epilepsy with clonic movements (spasms) in muscles on one side marching systematically through adjacent muscle groups. Named for London neurologist John Hughlings Jackson (1835-1911).
    Jail fever: Epidemic typhus, a severe acute (sudden-onset) infectious disease with prolonged high fever up to 40° C (104° F), intractable headache, and a pink-to-red raised rash. The cause is a microorganism called Rickettsia prowazekii. It is found worldwide and is transmitted by lice. The lice become infected on typhus patients and transmit illness to other people. The mortality increases with age and over half of untreated persons age 50 or more die. Also called European, classic, or louse-borne typhus.
    Jakob-Creutzfeldt disease: A transmissible degenerative brain disorder technically termed spongiform encephalopathy. Eating "mad cow" meat or squirrel brain can lead to Jaqcob-Creuzfeldt-like disease. Jakob-Creutzfeldt disease, better known as Creutzfeldt-Jakob disease (CJD), a dementing disease of the brain. It is believed due to an unconventional, transmissible agent (a prion). Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome, Jakob’s disease, and spastic pseuodoparalysis.
    Jakob’s disease: Better known as Creutzfeldt-Jakob disease (CJD), a dementing disease of the brain. It is believed due to an unconventional, transmissible agent (a prion). Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome, Jakob-Creutzfeldt disease, and spastic pseuodoparalysis.
    jamais vu: From the French, meaning "never seen". The illusion that the familiar does not seem familiar. The opposite of the feeling of "déjà vu."
    Jaundice: Jaundice is a yellowish staining of the skin and white of the eyes (sclerae) with pigment of bile. Jaundice can be an indicator of liver or gallbladder disease or result from red blood cells rupturing (hemolysis).
    Jaw: The bones below the mouth (the mandible) and the bone above the mouth just above the mouth (the maxilla). The word jaw came from the Anglo-Saxon ceowan meaning to chew.
    Jejunal: Having to do with the jejunum.
    Jejunum: Part of the small intestine. It is half-way down the small intestine between its duodenum and ileum sections.
    Joint: A joint is the area where two bones are attached for the purpose of motion of body parts.
    Joint hypermobility syndrome: A common benign childhood condition involving hypermobile joints (that can move beyond the normal range of motion). Symptoms include pains in knees, fingers, hips, and elbows. The affected joints may sprain or dislocate. Scoliosis (curvature of the spine) is more frequent. Usually improves with adulthood. Also called the hypermobility syndrome.
    Joint, tempero-mandibular: Joint that hinges the lower jaw (mandible) to the skull. Abbreviated TMJ or TM joint.
    Joint, TM: The joint that hinges the lower jaw (mandible) to the skull.
    Jugular: The principal vein in the front of either side of the neck. The word comes from the Latin jugulum meaning throat. The jugular is "the vein of the throat" or in ancient times "the sacrificial vein."
    Juvenile: Between infantile and adult as, for example, in juvenile rheumatoid arthritis (onset before age 16 years).
    Juvenile chronic arthritis, systemic-onset: See: Juvenile rheumatoid arthritis, systemic-onset (Still’s disease).
    Juvenile rheumatoid arthritis, systemic-onset (Still’s disease): Also known as systemic-onset juvenile chronic arthritis. Still’s disease presents with systemic (bodywide) illness including high intermittent fever, a salmon-colored skin rash, swollen lymph glands, enlargement of the liver and spleen, and inflammation of the lungs (pleuritis) and around the heart (pericarditis). The arthritis may not be immediately apparent.

  • Kala-azar: (Hindi for black fever). A disease of the vicera, particularly the liver, spleen, bone marrow and lymph nodes, due to infection be a parasite (called Leishmania). Also known as visceral leishmaniasis.
    Kaposi's sarcoma: A relatively rare type of cancer that develops on the skin of some elderly persons or those with a weak immune system, including those with acquired immune deficiency syndrome (AIDS).
    Kartagener's syndrome: The trio of sinusitis, bronchitis and situs inversus (lateral reversal of the position all organs in the chest and abdomen with the heart and stomach on the right, the liver on the left, etc.--opposite or "inverted" from their usual position).
    Karyotype: A standard arrangement of the chromosome complement, done for chromosome analysis.
    Karyotyping: Chromosome study.
    Karyotyping, flow: Use of flow cytometry to analyze and/or separate chromosomes on the basis of their DNA content. Flow cytometry detects the light- absorbing or fluorescing properties of chromosomes passing in a narrow stream through a laser beam and with automated sorting devices can sort successive droplets of the stream into different fractions depending on the fluorescence emitted by each droplet.
    Kawasaki’s disease: A syndrome of unknown origin, mainly affecting young children, causing fever, reddening of the eyes (conjunctivitis), lips and mucous membranes of the mouth, ulcerative gum disease (gingivitis), swollen glands in the neck (cervical lymphadenopathy), and a rash that is raised and bright red (maculoerythematous) in a glove-and-sock fashion over the skin of the hands and feet which becomes hard, swollen (edematous), and peels off. Also called mucocutaneous lymph node syndrome.
    Kb: Abbreviation for kilobase.
    Keloid: A tough raised scar.
    Keratin: Protein in the upper layer of the skin, hair, nails and animal horns. The word keratin comes from the Indo-European ker meaning horn.
    Keratitis: Inflammation of the cornea (transparent structure at the front of the eye).
    Kerato-: A confusing prefix it can refer to the cornea (as in keratitis and keratocornea) or to "horny" tissue (as in keratin and keratosis).
    Keratoconjunctitis: Inflammation of the eye involving both the cornea and conjunctiva.
    Keratoconus: Cone-shaped cornea with the apex of the cone being forward. Also called conical cornea.
    Keratoma: A callus.
    Keratoplasty: Corneal transplant.
    Keratosis: A localized overgrowth of the upper layer of skin. Common forms of keratosis include aging (senile keratosis) and sun exposure (actinic keratosis).
    Keratotomy: A surgical incision (cut) of the cornea. A radial keratotomy is a surgical procedure designed to flatten the cornea and thereby correct myopia (nearsightedness). It is called a radial keratotomy because the incisions resemble the spokes in a bicycle wheel.
    Kernicterus: Disorder due to jaundice in a newborn baby with high blood levels of the pigment bilirubin that is deposited in the brain resulting in damage. The level of bilirubin is monitored in newborns to determine whether treatment is needed to prevent kernicterus. With brain affected, it is also called bilirubin encephalopathy.
    Keshan disease: Condition caused by deficiency of the essential mineral selenium. Keshan disease is a potentially fatal form of cardiomyopathy (disease of the heart muscle). It was first observed in Keshan province in China and since has been found elsewhere (including New Zealand and Finland) in areas where the selenium level in the soil is low.
    Ketoacidosis: Ketosis (accumulation of substances called ketone bodies in the blood) plus acidosis (increased acidity of the blood). Ketoacidosis occurs when diabetes is not controlled.
    Kidneys: The kidneys are a pair of organs located in the right and left side of the abdomen which clear "poisons" from the blood, regulate acid concentration and maintain water balance in the body by excreting urine. The urine then passes through connecting tubes called "ureters" into the bladder. The bladder stores the urine until it is released during urination.
    Kilobase: Unit of length of DNA equal to 1000 nucleotide bases.
    Kindred: The extended family.
    Kinky hair syndrome: Genetic disorder with fragile twisted ("kinky") hair and progressive deterioration of the brain. Due to an error in copper transport resulting in copper deficiency. Females are carriers and their sons with the gene have the disease. Also known as Menkes syndrome.
    Kinship: Relationship by marriage or, specifically, a blood tie.
    Kissing bugs: Insect vectors (carriers) of the parasite (called Trypanosoma cruzi) which causes Chagas' disease (American trypanosomiasis). The reduviid bugs "kiss" people, especially babies, on the lips while they are asleep infecting them with their parasite. Over 20 million people in the Americas have Chagas disease. The parasite can also be transmitted by blood transfusion and cross the placenta during pregnancy to infect the fetus.
    Kissing disease: A name for infectious mononucleosis ("mono"), a very common illness caused by the Epstein-Barr virus (EBV). By the time most people reach adulthood, an antibody against EBV can be detected in their blood meaning they have been infected with EBV. The illness is less severe in young children. The infection can be spread by saliva. The incubation period for "mono" is 4 to 8 weeks. Symptoms include fever, fatigue, sore throat, and swollen lymph glands. "Mono" can cause liver inflammation (hepatitis) and spleen enlargement. Vigorous contact sports should be avoided to prevent spleen rupture.
    Klebsiella: A group of bacteria normally living in the intestinal tract and frequently the cause of nosocomial infections (infections acquired in the hospital). Named for Dr. Klebs.
    Kleeblattschadel: German for cloverleaf skull
    Klinefelter syndrome: The most common single cause of hypogonadism (underfunction of the gonads) and infertility in men, Klinefelter syndrome is due to a chromosome abnormality with XXY (plus additional X or Y chromosomes). It affects about 1 in 500 males and results in small testes (hypogenitalism), underproduction of testosterone and infertility (hypogonadism), and a long-limbed, long-trunked, relatively tall, slim build. Klinefelter boys tend to have learning and/or behavioral problems. At adolescence there is little growth of facial hair and a third of boys develop gynecomastia (enlargement of the male breast). Named for the physician Harry Klinefelter who with E.C. Reifenstein, Jr. and Fuller Albright (the founder of modern endocrinology) described the condition in 1942 long before its chromosomal basis became known.
    Klippel-Feil sequence/syndrome: The combination of short neck, low hairline at the nape of the neck and limited movement of the head. It is due to a defect in the early development of the spinal column in the neck (the cervival vertebrae).
    Klinefelter syndrome: A condition in males due to XXY sex chromosomes (plus sometimes additional X or Y chromosomes) resulting in small testes, insufficient production of testosterone, and infertility. Klinefelter boys tend to have learning and/or behavioral problems.
    Knee: See genu.
    Knee bursitis: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are three major bursae of the knee. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery.
    Knee jerk: The reflex tested by tapping just below the bent knee on the patellar tendon to cause the quadriceps muscle to contract and bring the lower leg forward. It has given rise to the saying: a knee-jerk reaction. Also known medically as the patellar reflex.
    Knock-knees: In medicalese: there are no knock-knees. The condition is genu valgum.
    Knuckle: The dorsal aspect of the flexed metacarpophalangeal joint. Knuckle may be shorter and simpler to say.
    Krukenberg tumor: A tumor of the ovary caused by the spread of stomach cancer.
    Kuru: A slowly progressive fatal disease of the brain (a form of subacute spongiform encephalopathy) due to an infectious agent (a virus or subviral particle called a prion) transmitted among people in Papua New Guinea by ritual canabalism. The discovery of the basis of Kuru is one of the more interesting detective stories of 20th-century medicine.
    Kussmaul breathing: Air hunger.
    Kwashiorkor: The word kwashiorkor comes from the Ivory Coast. It means the deposed (no longer suckled) child. Kwashiorkor is a childhood disease due to protein deprivation. Early signs are vague: apathy (indifference), lethargy (drowsiness) and irritability. More advanced signs are poor growth, lack of stamina, loss of muscle mass, swelling, abnormal hair (sparse, thin, often streaky red or gray in dark-skinned children) and abnormal skin (darkening in irritated but not sun-exposed areas). Kwashiorkor disables the immune system so the child is susceptible to a host of infectious diseases. Kwashiorkor is responsible for much morbidity (illness) and mortality (death) among children worldwide. Also known as protein malnutrition. and protein-calorie malnutrition (PCM).
    Kyphoscoliosis: Combination of kyphosis and scoliosis (lateral curving of the spine). Part of good health maintenance is to check a child's back (from infancy through adolescence) to make sure the back looks normal and, if concerned, a doctor is consulted.
    Kyphosis: Humpback.

  • Labia: Latin for lips. There are two pairs of labia (lips) at the entrance to the vagina. They are the labia majora (the larger outside pair) and the labia minora (the smaller inside pair). Together they form part of the vulva (the female external genitalia).
    Labia majora: The larger (major) outside pair of labia (lips) of the vulva (the female external genitalia).
    Labia minora: The smaller (minor) inside pair of labia (lips) of the vulva (the female external genitalia).
    Labial: Pertaining to the lips.
    Labile: Unstable.
    Labium: A lip. Labium is the singular of the Latin neuter noun meaning "a lip." The plural is labia.
    Labor: The journey of the baby and placenta (afterbirth) from the uterus to the vagina to the outside world. Synonymous with childbirth, confinement, delivery, parturition, and travail (the French word for work).
    Labyrinth: The maze of canals in the inner ear. The labyrinth is the portion of the ear that is responsible for sensing balance. Inflammaton of the labyrinth (labyrinthitis) can be accompanied by vertigo.
    Labyrinthitis: Inflammation of the labyrinth.
    Laceration: Severed skin. A cut. Washing a cut or scrape with soap and water and keeping it clean and dry is all that is required to care for most wounds. Putting alcohol, hydrogen peroxide, and iodine into a wound can delay healing and should be avoided. Seek medical care early if you think that you might need stitches. Any delay can increase the rate of wound infection. Any puncture wound through tennis shoes has a high risk of infection and should be seen by your healthcare professional. Any redness, swelling, increased pain, or pus draining from the wound may indicate an infection that requires professional care.
    Lacrimal: Pertaining to tears.
    Lacrimation: Shedding tears.
    Lactase: Enzyme that breaks down the milk sugar lactose.
    Lactase deficiency: Lack of the enzyme lactase resulting in failure to digest lactose in milk (lactose intolerance).
    Lactation: Giving milk.
    Lactobacillus: Literally milk bacteria, normally found in the mouth, intestinal tract and vagina.
    Lactobacillus acidophilus: Bug that produces acidophilus milk.
    Lactose intolerance: inability to digest the milk sugar lactose.
    Lacuna: A small pit, cavity, defect or gap.
    Lamella: A thin leaf, plate, disk, wafer.
    Lamina: A plate or layer. For example, the lamina arcus vertebrae, usually just called the lamina, are plates of bone in each vertebral body.
    Lancet: Small pointed knife used to do a finger prick for a blood test. Also the name of a medical journal in England.
    Lanugo: The fine hair on the body of a newborn baby.
    Laparoscopy: Laparoscopy is a type of surgery where small incisions are made in the abdominal wall through which instruments are placed that can help in visualizing structures in the abdomen and pelvis.
    Laparotomy: An operation to open the abdomen.
    Large cell carcinoma: A group of lung cancers in which the cells are large and look abnormal.
    Large intestine: Comes after the small intestine. Large because it is wider than the small intestine.
    Laryngeal: Having to do with the larynx.
    Laryngeal papilloma: A warty growth in the larynx, ususally on the vocal cords. Persistent hoarseness is a common symptom.
    Laryngeal papillomatosis: Numerous warty growths on the vocal cords. Most common in young children. Recurrences are, unfortunately, frequent. Remission may occur after several years. The disease can be due to the baby contracting human papilloma virus (HPV) during birth through the vaginal canal from a mother with genital warts (which are due to HPV). Each year, about 300 infants are born with the virus on their vocal cords because of maternal transmission.
    Laryngectomee: A person who has had his or her voice box removed.
    Laryngectomy: An operation to remove all or part of the larynx.
    Laryngitis: Inflammation of the larynx (voice box).
    Laryngomalacia: A soft floppy larynx.
    Laryngoscope: A flexible, lighted tube used to examine the larynx.
    Laryngoscopy: Examination of the larynx with a mirror (indirect laryngoscopy) or with a laryngoscope (direct laryngoscopy).
    Laryngostasis: More commonly known as croup. An infection of the larynx, trachea, and the bronchial tubes, largely in children. Caused usually by viruses, less often by bacteria. Symptoms include a cough that sounds like a barking seal and a harsh crowing sound during inhaling. Treatment can include moist air, salt water nose drops, decongestants and cough suppressants, pain medication, fluids, and occasionally antibiotics. The major concern in croup is breathing difficulty as the air passages narrow. Close monitoring of the breathing of a child with croup is important, especially at night. While most children recover from croup without hospitalization, some children can develop life-threatening breathing difficulties. Therefore, close contact with the doctor during this illness is important.
    Larynx: The larynx is the portion of the breathing, or respiratory, tract containing the vocal cords which produce vocal sound. It is located between the pharynx and the trachea. It is also called the "voice box." Its outer wall of cartilage forms the area of the front of the neck referred to as the "Adams apple."
    Laser: A powerful beam of light used in some types of surgery to cut or destroy tissue.
    Lateral: The side of the body or body part that is farther from the middle or center (median) of the body. Typically, lateral refers to the outer side of the body part, but it is also used to refer to the side of a body part. For example, when referring to the knee, lateral would mean the side of the knee that is farthest from the opposite knee. The opposite of lateral is medial.
    Lavage: Washing out. Gastric lavage is washing out the stomach, for example, to remove drugs or poisons.
    Lazy eye: An eye that diverges in gaze. More formally called strabismus. Can be esotropia (cross-eyed) or exotropia (wall-eyed).
    lb.: The abbreviation for pound, the measure of weight, lb. (plural: lb. or lbs.) stands for "libra" (Latin for pound).
    LDL: Low-density lipoprotein.
    LDL cholesterol: Low-density lipoprotein cholesterol (the "bad" cholesterol).
    Lead poisoning: An environment hazard (for example, from lead-containing paint, leaded gasoline,etc) capable of causing brain damage.
    Legg-Perthes disease: A hip disorder in children due to interruption of the blood supply to the head of the femur (the ball in the ball-and-socket hip joint). Also called Legg disease and Legg-Calve-Perthes disease.
    Legionaire's disease: A disease (first identified at the 1976 American Legion convention) due to bacteria (Legionella) found in plumbing, shower heads and water-storage tanks. Outbreaks of Legionella pneumonia have been attributed to evaporative condensors and cooling towers.
    Legionella: The bacteria causing Legionaire's disease.
    Leiomyoma: A benign tumor of smooth muscle, the type of muscle found in the heart and uterus. A leiomyoma of the uterus is commonly called a fibroid.
    Leiomyosarcoma: a malignant tumor of smooth muscle origin. Smooth muscle is the major structural component of most hollow internal organs and the walls of blood vessels. Can occur almost anywhere in the body but is most frequent in the uterus and gastrointestinal tract. Complete surgical excision, if possible, is the treatment of choice.
    Leishmania: A group of parasites causing considerable human disease (leishmaniasis).
    Leishmaniasis: Diseases due to Leishmania involving the organs (kala-azar), skin plus mucous membranes (espundia), or skin alone (usually named for the place plus boil, button or sore as, for example, Jericho boil, Bagdad button, Dehli sore).
    Lennox syndrome: See Lennox-Gastaut syndrome.
    Lennox-Gastaut syndrome: A severe form of epilepsy that usually begins in early childhood and is characterized by frequent seizures of multiple types, mental impairment, and a particular brain wave pattern (a slow spike-and-wave pattern). The seizures that are notoriously hard to treat and may lead to falls and injuries can be reduced in frequency by treatment with lamotrigone, a chemically novel antiepileptic drug. The syndrome is named for W.G. Lennox and H. Gastaut who described it.
    Leprosy: A skin infection caused by a bacteria, which can also be associated with nerve damage. The bacteria involved is called Mycobacterium leprae.
    Lesbian: Female homosexual. The name "lesbian" comes from the Greek island of Lesbos in the Aegian Sea where in antiquity the women were said to be homosexual. The poet Sappho who lived on Lesbos (circa 600 BC) was a lesbian in both geographic location and sexual orientation.
    Lesbianism: Female homosexuality. Also called sapphism (after the lesbian poet Sappho).
    Lesion: An area of abnormal tissue change.
    Lethal: Deadly.
    Lethargy: Abnormal drowsiness, stupor.
    Leucemia: See leukemia.
    Leukemia: Cancer of the blood cells.
    Leukemia, accelerated phase of: Refers to chronic myelogenous leukemia that is progressing. The number of immature, abnormal white blood cells in the bone marrow and blood is higher than in the chronic phase, but not as high as in the blast phase.
    Leukemia, smoldering: A condition in which the bone marrow does not function normally. It does not produce enough blood cells. This condition may progress and become acute leukemia. Smoldering leukemia also is called myelodysplastic syndrome or preleukemia.
    Leukemoid reaction: A benign blood picture resembling leukemia. For example, in infectious mononucleosis.
    Leuko-: Prefix meaning white.
    Leukocytes: Cells that help the body fight infections and other diseases. Also called white blood cells (WBCs).
    Leukocyte count: A white blood cell (WBC) count.
    Leukocytosis: Increase in the number of white blood cells.
    Leukodystrophy: Disorder of the white matter of the brain. The white matter mainly consists of nerve fibers (not the nerve cells themselves) and is concerned with conduction od nerve impulses.
    Leukopenia: Shortage of white blood cells.
    Leukoplakia: A white spot or patch in the mouth.
    Levo-: From the Latin laevus meaning on the left side. For example, a molecule that shows levorotation is turning or twisting to the left. The opposition of levo- is dextro- (from the Latin dexter meaning on the right side) so the opposite of levorotation is dextrorotation.
    Levocardia: Reversal of all of the abdominal and thoracic organs (situs inversus) except the heart which is still in its usual location on the left. This situation is far more of an anatomic mess than when all the organs including the heart are reversed to create a complete mirror image. Levocardia virtually always results in congenital heart disease (malformation of the heart or great vessels).
    LHRH agonists: Compounds that are similar to LHRH (luteinizing hormone-releasing hormone).
    Libido: The word "libido" in Latin means "desire, longing, fancy, lust, or rut." Although the adjective "libidinous" meaning lustful has been used in English for 500 or so years, "libido" made a belated entry into the English language in1913, thanks to Sigmund Freud and other psychoanalysts who applied the term to psychic energy or drive, especially the sexual instinct.
    Library: In genetics, a library is an unordered collection of clones (i.e., cloned DNA from a particular organism), whose relationship to each other can be established by physical mapping. For example, you can have an E. coli library or a human DNA library. Among the types of libraries, there are genomic libraries and arrayed libraries. (See Library, genomic and Library, arrayed).
    Library, arrayed: In genetics, arrayed libraries of DNA clones are used for many purposes, including screening for a specific gene or genomic region of interest as well as for physical mapping. An arrayed library consists of (in technical terms) individual primary recombinant clones (which are hosted in phage, cosmid, YAC, or another vector) that have been placed in two-dimensional arrays in microtiter dishes (plastic dishes with an orderly array of tiny wells). Each primary clone can be identified by the identity of the plate and the clone location (row and column) on that plate. The information gathered on individual clones from various genetic linkage and physical map analyses is then entered into a relational database and used to construct physical and genetic linkage maps.
    Library, genomic: A collection of DNA clones made from a set of randomly generated overlapping DNA fragments representing the entire genome of an organism. As a molecular genetic sequel to John Steinbeck’s "Of Mice and Men", today you can have a mouse genomic library or a human genomic library.
    Li-Fraumeni syndrome: A family tendency to cancers due to a mutation in a gene that normally serves to curb cancer: the p53 tumor-suppressor gene.
    Ligament: A ligament is a band or sheet of connective tissue that connects two bones together.
    Ligate: To tie. As, for example, the surgeon ligated the artery.
    Ligature: Material (silk, gut, wire, etc) used to ligate.
    Limb: The arm or leg.
    Lingual: Having to do with the tongue.
    Linkage: Tendency for genes to be inherited together because of their location near one another on the same chromosome.
    Linkage analysis: Study aimed at establishing linkage between genes. Today linkage analysis serves as a way of gene-hunting and genetic testing.
    Linkage map: A map of the genes on a chromosome based on linkage analysis. A linkage map does not show the physical distances between genes but rather their relative positions, as determined by how often two gene loci are inherited together. The closer two genes are (the more tightly they are linked), the more often they will be inherited together. Linkage distance is measured in centimorgans (cM).
    Lipid: Fatty substance.
    Lipid storage diseases: A series of disorders due to inborn errors in lipid metabolism resulting in the abnormal accumulation of lipids in the wrong places (Examples include Gaucher, Fabry and Niemann-Pick diseases and metachromatic leukodystrophy).
    Lipid profile: Pattern of lipids in the blood. (A lipid profile usually includes the total cholesterol, high density lipoprotein (HDL) cholesterol, triglycerides, and the calculated low density lipoprotein (LDL) cholesterol.
    Lipoma: A benign fatty tumor.
    Lipoprotein: A complex of lipid and protein, the way lipids travel in the blood.
    Lips: Aside from the lips of the mouth, there are two pairs of lips at the entrance to the vagina. They are the labia majora (the larger outside pair) and the labia minora (the smaller inside pair). Together they form part of the vulva (the female external genitalia).
    Listeria: A group of bacteria named after the English surgeon and apostle of antisepsis, Joseph Lister (1827-1912).
    Listeriosis: Infection with one of the Listeria bacteria capable of causing miscarriage (spontaneous abortion), stillbirth and premature birth.
    Litho-: Prefix meaning stone.
    Lithotomy: Surgical removal of a stone.
    Lithotripsy: Procedure to break a stone into small particles that can be passed in the urine.
    Liver: An organ in the upper abdomen that aids in digestion and removes waste products and worn-out cells from the blood.
    Livid: Black and blue.
    Living will: A living will is one form of advance medical directive. Advance medical directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There are two basic types of advance directives: (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for health-care decision-making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society).
    Lobar: Having to do with a lobe. For example, lobar pneumonia.
    Lobe: 1. A subdivision of an organ, divided by fissures, connective tissue or other natural boundaries. 2. A rounded projecting portion, such as the lobe of the ear.
    Lobectomy: An operation to remove an entire lobe of the lung.
    Lobule: A little lobe.
    Local therapy: Treatment that affects only a tumor and the area close to it.
    Local treatment: Treatment that affects the tumor and the area close to it.
    Lochia: The fluid that weeps from the vagina for a week or so after delivery of a baby.
    Lockjaw: See Tetanus.
    Locomotion: Moving from one place to another.
    Locus: The place, in Latin.. In genetics, a locus is the place a gene occupies on a chromosome. One locus, two loci.
    Locus minoris resistentiae: A place of less resistance, in Latin. For example, a damaged heart valve may act as a locus minoris resistentiae where bacteria released into the blood stream (bacteremia) tend to settle.
    Loin: The portion of the lower back from just below the ribs to the pelvis.
    Longevity: Lifespan. (With increasing longevity, women will soon be postmenopausal for one third of their lives).
    Longitudinal: The word come from the Latin longitudo meaning length. Hence, longitudinal means along the length, running lengthwise, or (by extension) over the course of time.
    Longitudinal section: A section that is cut along the long axis of a structure. The opposite is a cross section.
    Longitudinal study: A study done over the passage of time. For example, a longitudinal study of children with Down syndrome (trisomy 21) might involve the study of 100 children with this condition from birth to 10 years of age. Also called a diachronic study. The opposite of a cross-sectional (synchronic) study.
    Lordosis: Swayback.
    Louse-borne typhus: A severe acute disease with prolonged high fever up to 40° C (104° F), intractable headache, and a pink-to-red raised rash. The cause is a microorganism called Rickettsia prowazekii. It is found worldwide and is transmitted by lice. The lice become infected on typhus patients and transmit illness to other people. The mortality increases with age and over half of untreated persons age 50 or more die. Also called epidemic, European, classic typhus and jail fever.
    Lower GI series: A series of x-rays of the colon and rectum that is taken after the patient is given a barium enema. (Barium is a white, chalky substance that outlines the colon and rectum on the x-ray.)
    Low-set ear: An ear positionned below its normal location. Classified as a minor anomaly. Technically, the ear is low-set when the helix (of the ear) meets the cranium at a level below that of a horizontal plane through both inner canthi (the inside corners of the eyes). The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Lubricant: An oily or slippery substance. A vaginal lubricant may be helpful for women who feel pain during intercourse because of vaginal dryness.
    Lues: An old name for syphilis, a sexually transmitted disease (STD) that has been around for centuries and is caused by Treponema pallidum, a microscopic organism called a spirochete, a worm-like spiral-shaped organism that infects by burrowing into the moist mucous membranes of the mouth or genitals. From there, the spirochete produces the classic non-painful ulcer known as a chancre. There are 3 stages of syphilis. The first ("primary") stage is formation of the chancre.. It is highly contagious and can last 1-5 weeks. The disease can be transmitted from any contact with one of the ulcers, which are teeming with spirochetes. If the ulcer is outside the vagina or on the scrotum, the use of condoms may not help preventitransmission of the disease. Likewise, if the ulcer is in the mouth, merely kissing can spread syphilis. Even without treatment, an early infection resolves on its own in most women. However, 25% will proceed to the next stage of the disease called "secondary" syphilis, which lasts 4-6 weeks. This secondary phase can include hair loss, a sore throat, white patches in the nose, mouth, and vagina, fever, headaches, and a skin rash. There can be lesions on the genitals that look like genital warts but are caused by spirochetes rather than the wart virus. These wart-like lesions, as well as the skin rash, are highly contagious. The rash can occur on the palms of the hands and the infection can be transmitted by casual contact. The third stage of the disease involves the brain and heart and is usually no longer contagious. At this point, however, the infection can cause extensive damage to the internal organs, such as the brain, and can lead to death.
    Lumbar puncture: A lumbar puncture or "LP" is a procedure whereby spinal fluid is removed from the spinal canal for the purpose of diagnostic testing. It is particularly helpful in the diagnosis of inflammatory diseases of the central nervous system, especially infections, such as meningitis. It can also provide clues to the diagnosis of stroke, spinal cord tumor and cancer metastasis to the central nervous system.
    Lumpectomy: A lumpectomy is a partial mastectomy, and quadrentectomy refer to removing only a portion of the breast.
    Lungs: The lungs are a pair of breathing organs located with the chest which remove carbon dioxide from and bring oxygen to the blood. There is a right and left lung.
    Luteinizing hormone-releasing hormone: A hormone that controls sex hormones in men and women. Also called LHRH.
    Luxation: Complete dislocation of a joint. A partial dislocation is a subluxation.
    Lymph: The almost colorless fluid that travels through the lymphatic system and carries cells that help fight infection and disease.
    Lymph nodes: Small, bean-shaped organs located throughout the lymphatic system. The lymph nodes store special cells that can trap cancer cells or bacteria that are traveling through the body in lymph. Also called lymph glands.
    Lymphadenopathy: Disease of the lymph nodes.
    Lymphangiogram: X-rays of the lymphatic system. A dye is injected to outline the lymphatic vessels and organs.
    Lymphangioma: A structure consisting of a collection of blood vessels and lymph vessels that are overgrown and clumped together. Depending on their nature, these structures may grow slowly or quickly. They can cause problems because of their location. For example, a lymphangioma around the voicebox (larynx) might cause a breathing problem.
    Lymphatics: Lymphatics are small thin channels similar to blood vessels. They do not carry blood, but collect and carry tissue fluid from the body to ultimately drain back into the blood stream.
    Lymphatic system: The tissues and organs, including the bone marrow, spleen, thymus, and lymph nodes, that produce and store cells that fight infection and disease. The channels that carry lymph are also part of this system.
    Lymphedema: A condition in which excess fluid collects in tissue and causes swelling. It may occur in the arm or leg after lymph vessels or lymph nodes in the underarm or groin are removed.
    Lymphocytes: White blood cells that fight infection and disease.
    Lymphocytic: Referring to lymphocytes, a type of white blood cell.
    Lymphocytosis: Too many lymphocytes.
    Lymphoid: Referring to lymphocytes, a type of white blood cell. Also refers to tissue in which lymphocytes develop.
    Lymphoid tissue: The part of the body's immune system that helps protect it from bacteria.
    Lymphoma: Tumor of the lymphoid tissue.
    Lyon hypothesis: See Lyonizatioon.
    Lyonization: The inactivation of an X chromosome. One of the two X chromosomes in every cell in a female is randomly inactivated early in embryonic development. Named after geneticist Mary Lyon.
    Lysis: Destruction. Hemolysis (hemo-lysis) is the destruction of red blood cells with the release of hemoglobin.

    Lytic: Suffix having to do with lysis. For example, hemolytic anemia.
  • M proteins: Antibodies or parts of antibodies found in unusually large amounts in the blood or urine of multiple myeloma patients.
    Machine, heart-lung: A machine that does the work both of the heart (pump blood) and the lungs (oxygenate the blood). Used, for example, in open heart surgery. Blood returning to the heart is diverted through the machine before returning it to the arterial circulation. Also called a pump-oxygenator.
    Macro-: Prefix from the Greek makros meaning large or long. The opposite of micro-.
    Macrobiota: The living organisms (or flora and fauna) of a region that are large enough to be seen with the naked eye. From the Greek macro-, large + bios, life.
    Macrobiotic: Macrobiotic refers to the macrobiota, a region’s living organisms (or flora and fauna) large enough to be seen with the naked eye. However, macro- comes from the Greek "makros" meaning not only "large" but also "long". So macrobiotic can also be taken to mean "long life." Thus, the idea with a macrobiotic diet is that it is for a long life, that is that the diet will lengthen life.
    Macrocephaly: An abnormally large head.
    Macrocytic: Enlarged red blood cells (RBCs). Folic acid deficiency is one cause of macrocytic anemia.
    Macroglossia: Enlarged tongue.
    Macrophage: Type of white blood that takes in (ingests) foreign material. Macrophages are key players in the immune response to foreign invaders of the body, such as infectious microorganisms.
    Macroscopic: Large enough to be seen with naked eye. As opposed to microscopic. A big tumor may well be macroscopic while a tiny tumor is microcopic (cannot be seen without the aid of microscope).
    Macrosomia: Overly large body. A child with macrosomia has significant overgrowth.
    Macula: A small spot. A macula on the skin is a small flat spot while the macula in the eye is a small spot where vision is keenest in the retina.
    Magnesia: Named after a town in presentday Turkey where an ore containing magnesium carbonate was mined. Milk of Magnesia, the laxative, is magnesium hydroxide.
    Magnesium: A mineral involved in many processes in the body including nerve signaling, the building of healthy bones, and normal muscle contraction. Magnesium is contained in all unprocessed foods. High concentrations of magnesium are found in nuts, unmilled grains and legumes such as peas and beans. Magnesium deficiency can occur due to inadequate intake or impaired intestinal absorption of magnesium. It is often associated with low calcium (hypocalcemia) and low potassium (hypokalemia). Deficiency of magnesium causes increased irritability of the nervous system with tetany (spasms of the hands and feet, muscular twitching and cramps, spasm of the larynx, etc.). According to the National Academy of Sciences, the Recommended Dietary Allowances of magnesium are 420 milligrams per day for men and 320 milligrams per day for women. The upper limit of magnesium as supplements is 350 milligrams daily, in addition to the magnesium from food and water. Persons with impaired kidney function should be especially careful about their magnesium intake because they can accumulate magnesium, a dangerous situation.
    Magnesium deficiency: Can occur due to inadequate intake or impaired intestinal absorption of magnesium. Low magnesium (hypomagnesemia) is often associated with low calcium (hypocalcemia) and low potassium (hypokalemia). Deficiency of magnesium causes increased irritability of the nervous system with tetany (spasms of the hands and feet, muscular twitching and cramps, spasm of the larynx, etc.). According to the National Academy of Sciences, the Recommended Dietary Allowances of magnesium are 420 milligrams per day for men and 320 milligrams per day for women. The upper limit of magnesium as supplements is 350 milligrams daily, in addition to the magnesium from food and water.
    Magnesium excess: Persons with impaired kidney function should be especially careful about their magnesium intake because they can accumulate magnesium, a dangerous situation. According to the National Academy of Sciences, the Recommended Dietary Allowances of magnesium are 420 milligrams per day for men and 320 milligrams per day for women. The upper limit of magnesium as supplements is 350 milligrams daily, in addition to the magnesium from food and water.
    Magnetic resonance imaging (MRI): A procedure using a magnet linked to a computer to create pictures of areas inside the body.
    Maimonides' prayer: A prayer written by the 12th-century physician-philosopher Maimondes, like the famous oath of Hippocrates, is often recited by new medical graduates.
    Maintenance therapy: Chemotherapy that is given to leukemia patients in remission to prevent a relapse.
    Major histocompatabilty complex (MHC): A cluster of genes on chromosome 6 concerned with antigen production and critical to transplantation. The MHC includes the human leukocyte antigen (HLA) genes.
    Malabsorption: Poor intestinal absorption of nutrients.
    Malacia: Means softening. Osteomalacia is thus softening of bone (due to deficiency of calcium and vitamin D).
    Malady: From the French maladie for illness.
    Malaise: A vague feeling of discomfort, one that cannot be pinned down but is often sensed as "just not right." Malaise comes straight from the French who compounded it from "mal" (bad or ill) + "aise" (ease) = ill at ease.
    Malar: Referring to the cheek.
    Malaria: Infectious disease involving many million of people, caused by the protozoan parasite Plasmodium transmitted by the sting of the Anopheles mosquito or by a contaminated needle or transfusion. The name comes from the Italian mal'aria for bad air; the disease was thought due to bad air wafting from the swamps. Among the many names for malaria: are ague, jungle fever, marsh or swamp fever, and paludism.
    Malaria, falciparum: The most dangerous type of malaria. Persons carrying the sickle cell gene have some protection against malaria. Persons with a gene for hemoglobin C (another abnormal hemoglobin like sickle hemoglobin), thalassemia trait or deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD) are thought also to have partial protection against malaria.
    Male: The traditional definition of male was "an individual of the sex that produces sperm" (or some such). However, things are not so simple today. Male can be defined by physical appearance, by chromosome constitution (see Male chromosome complement), or by gender identification.
    Male chromosome complement: The large majority of males have a 46, XY chromosome complement (46 chromosomes including an X and a Y chromosome). A minority of males have other chromosome constitutions such as 47,XXY (47 chromosomes including two X chromosomes and a Y chromosome) and 47,XYY (47 chromosomes including an X and two Y chromosomes).
    Malignancy: A tumor that is malignant.
    Malignant: Malignant means to resistant to treatment, or severe (As in "malignant hypertension"). When referring to an abnormal growth it implies a tendency to metastasize. The word malignant comes the Latin combination of mal meaning bad and nascor meaning to be born; malignant literally means born to be bad.
    Malignant giant cell tumor: A type of bone tumor.
    Malignant melanoma: See melanoma
    Malleolus: Bony prominence on either side of the ankle.
    Malleus: Tiny bone truly shaped like a minute mallet in the middle ear.
    Malrotated ear: An ear that is slanted more than usual. Technically, an ear is slanted when the angle of the slope of the auricle is more than 15 degrees from the perpendicular. Slanted ears are considered a minor anomaly. The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Malrotation of the intestine: Failure for the intestine to rotate normally during embryonic development.
    Mammary gland: Breast (male or female).
    Mammogram: An x-ray of the breast.
    Mandible: The mandible is the the bone of the lower jaw. The joint where the mandible meets the upper jaw at the temporal bone is called the temporomandibular joint.
    Mania, symptoms: Symptoms of mania include *Inappropriate elation. *Inappropriate irritability. *Severe insomnia. *Grandiose notions. *Increased talking speed and/or volume. *Disconnected and racing thoughts. *Increased sexual desire. *Markedly increased energy. *Poor judgment. *Inappropriate social behavior.
    Manic: Refers to a mood disorder in which a person seems "high", euphoric, expansive, sometimes agitated, hyperexcitable, with flights of ideas and speech.
    Manic-depression: Alternating moods of abnormal highs (mania) and lows (depression). Called bipolar disease because of the swings between these opposing poles in mood.
    Manic-depressive disease: See manic-depression.
    Map, contig: A map depicting the relative order of a linked library of small overlapping clones representing a complete chromosome segment.
    Map, linkage: A map of the genes on a chromosome based on linkage analysis. A linkage map does not show the physical distances between genes but rather their relative positions, as determined by how often two gene loci are inherited together. The closer two genes are (the more tightly they are linked), the more often they will be inherited together. Linkage distance is measured in centimorgans (cM).
    Map, physical: A map of the locations of identifiable landmarks on chromosomes. Physical distance is measured in base pairs. The physical map differs from the genetic map which is based purely on genetic linkage data. In the human genome, the lowest-resolution physical map is the banding patterns of the 24 different chromosomes. The highest-resolution physical map is the complete nucleotide sequence of all chromosomes, a future goal.
    Maple syrup urine disease (MSUD): Hereditary disease due to deficiency of an enzyme involved in amino acid metabolism, characterized by urine that smells like maple syrup.
    Mapping, gene: Charting the positions of genes on chromosome and learning the distance, in linkage units or physical units, between genes.
    Marasmus: Wasting away, as occurs with children who have kwashiorkor. Also called cachexia, is usually a result of protein and calorie deficiency.
    Mapping: Charting the location of genes on chromosomes.
    Marfan syndrome: Inherited disorder with long fingers and toes, dislocation of the lens, and aortic wall weakness and aneurysm. (It has been suggested that Abraham Lincoln had Marfan syndrome.)
    Marker: An identifiable heritable spot on a chromosome. A marker can be an expressed region of DNA (a gene) or a segment of DNA with no known coding function. All that matters is that the marker can be monitored.
    Marker chromosome: An abnormal chromosome that is distinctive in appearance but not fully identified. For example, the fragile X chromosome was once called the marker X.
    Marriage, cousin: A form of consanguinity. Everyone carries recessive alleles, genes that are generally innocuous in the heterozygous state but that in the company of another gene of the same type are capable of causing disease. We are all genetic reservoirs for genetic disease. Since first cousins share a set of grandparents, for any particular allele (gene) in the father, the chance that the mother inherited the same allele from the same source is 1/8. And for any gene the father passes to his child, the chance is 1/8 that the mother has the same gene and ½ that she transmits it to the child, so 1/8 X ½ = 1/16. A first-cousin marriage therefore has a coefficient of inbreeding of 1/16. The added risks for first cousins depend not only upon this coefficient of inbreeding but also upon their genetic family histories and, in some cases, upon test results (for example, for the risk of beta thalassemia in first cousins of Greek or Italian descent). There are always added risks from the mating of closely related persons.
    Marrow: The bone marrow.
    Marsh fever: See malaria.
    Masochism: Pleasure from one's own pain. Named after the 19th-century Austrian writer Leopold von Sacher-Masoch (masoch-ism).
    Masseter: The muscle that raises the lower jaw.
    Mast cell: A connective tissue cell whose normal function is unknown, the mast cell is frequently injured during allergic reactions, releasing strong chemicals including histamine into the tissues and blood that are very irritating and cause itching, swelling, and fluid leaking from cells. These allergic chemicals can also cause muscle spasm and lead to lung and throat tightening as is found in asthma and loss of voice.
    Mastectomy: Mastectomy is a general term for removal of the breast. A modified radical mastectomy involves removal of the breast and the axillary lymph nodes. A simple mastectomy removes the breast, but not the lymph nodes.
    Masticate: To chew.
    Mastitis: Inflammation of the breast.
    Mastoid: The rounded protrusion of bone just behind the ear once thought to look like the breast. The word comes from the Greek mastos meaning breast + -oid= breast-like.
    Mastoiditis: Inflammation of the mastoid, often secondary to ear infection.
    Maternal mortality rate: The number of maternal deaths related to childbearing divided by the number of live births (or by the number of live births + fetal deaths) in that year. The maternal mortality rate in the United States in 1993 (and 1994) was 0.1 per 1,000 live births, or 1 mother dying per 10,000 live births.
    Maternal serum alpha-fetoprotein: A plasma protein, alpha-fetoprotein (AFP) is normally produced by the fetus. The level of AFP in the blood serum of pregnant women provides a screening test for open neural tube defects (anencephaly and spina bifida) and for Down syndrome (and other chromosome abnormalities). The maternal serum AFP (MSAFP) tends to be unusally high with open neural tube defects and unsually low with Down syndrome.
    Matter, gray: The cortex of the brain which contains nerve cell bodies. The gray matter is as opposed to the white matter, the part of the brain that contains myelinated nerve fibers. The gray matter is so named because it in fact appears gray. In "The Mysterious Affair at Styles" (1920), Agatha Christie first quoted the fictional Belgian detective Hercule Poirot in regard to his gray matter: "’This affair must be unravelled from within.’ He tapped his forehead. ‘These little grey cells. It is "up to them"—as you say over here.’"
    Matter, white: The part of the brain that contains myelinated nerve fibers. The white matter is white because it is the color of myelin, the insulation covering the nerve fibers. The white matter is as opposed to the gray matter (the cortex of the brain which contains nerve cell bodies).
    Maxilla: The maxilla is the major bone of the upper jaw
    Measles: Rubeola or the hard (or 10-day) measles. The name measles comes from the Middle English maselen meaning many little spots referring, of course, to the rash.
    Measles immunization: The standard MMR vaccine is given to prevent measles, mumps and rubella (German measles). The MMR vaccine is now given in two dosages. The first should be given at12-15 months of age. The second vaccination should be given at 4-6 years (or, alternatively, 11-12 years) of age. Most colleges require proof of a second measles or MMR vaccination prior to entrance. Most children should receive MMR vaccinations. Exceptions may include children born with an inability to fight off infection, some children with cancer, on treatment with radiation or drugs for cancer, on long term steroids (cortisone). People with severe allergic reactions to eggs or the drug neomycin should probably avoid the MMR vaccine. Pregnant women should wait until after delivery before being immunized with MMR. People with HIV or AIDS should normally receive MMR vaccine. Measles, mumps, and rubella vaccines may be administered as individual shots, if necessary, or as a measles-rubella combination.
    Measly: The word measly can refer to measles, and, thence, to spotty and, thence, to something that is of little value. In medicine, the measly tapeworn is the pork tapeworm (T. solium) which can be contracted through eating measly pork (pork infected with the larval form of T. solium).
    Measly tapeworm: The pork tapeworm, formally known as Taenia solium. Contracted from undercooked or measly pork (pork infected with the larval forms of the tapeworm). Can grow to be 3-6 feet (0.9-1.8 m) long in the human intestine. Also known as the armed tapeworm.
    Meatus: A passageway.
    Meconium: Dark sticky material normally present in the intestine at birth and passed in the feces after birth. The passage of meconium before birth can be a sign of fetal distress.
    Meckel's diverticulum: An out-pouching of the small bowel (ileum). Present in about 2% of people and usually occurs about 2 feet before the junction with the colon. Can be lined by stomach-type mucosa and ulcerate, perforate, or cause small bowel obstruction.
    Medial: The side of the body or bdy part that is nearer to the middle or center (median) of the body. For example, when referring to the knee, medial would mean the side of the knee that is closest to the other knee The opposite of medial is lateral.
    Median: The middle. Like the median strip in a highway.
    Mediastinoscopy: A procedure in which the doctor inserts a tube into the chest to view the organs in the mediastinum. The tube is inserted through an incision above the breastbone.
    Mediastinotomy: A procedure in which the doctor inserts a tube into the chest to view the organs in the mediastinum. The tube is inserted through an incision next to the breastbone.
    Mediastinum: The area between the lungs. The organs in this area include the heart and its large veins and arteries, the trachea, the esophagus, the bronchi, and lymph nodes.
    Medical directives, advance: Advance directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There ared two basic types of advance directives: (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for health-care decision-making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society).
    Medical Research Council (MRC): Key government agency for medical research in the U.K..
    Medication, ACE-inhibitor: Agents that inhibit ACE (angiotensin converting enzyme), thereby acting as vasodilators (really as anti-vasoconstrictors), lightening the stress load on the heart.
    Medication, anti-coagulant: Blood thinners. Drugs, like heparin and warfarin, used as "blood-thinners" to prevent blood clots and to maintain open blood vessels.
    Medication, anti-platelet: Platelet-blocking drugs. Drugs that, like aspirin, reduce the tendency of platelets in the blood to clump and clot.
    Medication, beta-blocker: Drugs that antagonize the action of adrenaline (a beta adrenergic substance) and relieve stress to the heart muscle. Beta-blockers are often used to slow the heart rate or lower the blood pressure.
    Medication, clot-dissolving: Drugs used to dissolve blood clots. Agents such as plasminogen-activator (t-PA) and streptokinase that are effective in dissolving clots and re-opening arteries. Used, for example, in the treatment of heart attacks. Clot-dissolvers are also called thrombolytic agents.
    Medication, vasodilator: Drugs that act as blood vessel dilator (vasodilators) and open vessels by relaxing their muscular walls). For example, nitroglycerin is a vasodilator. So are the ACE (angiotensin converting enzyme) inhibitors.
    Mediterranean anemia: Better known today as thalassemia (or as beta thalassemia or thalassemia major) .The clinical picture of this important type of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley. The name thalassemia was coined by the Nobel Prize winning pathologist George Whipple and the professor of pediatrics Wm Bradford at U. of Rochester because thalassa in Greek means the sea (like the Mediterrranean Sea) + -emia means in the blood so thalassemia means sea in the blood. Thalassemia is not just one disease. It is a complex contingent of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of normal adult hemoglobin is made up of 2 alpha and 2 beta polypeptide chains. In beta thalassemia, there is a mutation (change) in both beta globin chains leading to underproduction (or absence) of beta chains, underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin (for example, from Italy and Greece). Children with this disease inherit one gene for it from each parent. The parents are carriers (heterozygotes) with just one thalassemia gene, are said to have thalassemia minor, and are essentially normal. Their children affected with beta thalassemia seem entirely normal at birth because at birth we still have predominantly fetal hemoglobin which does not contain beta chains. The anemia surfaces in the first few months after birth and becomes progressively more severe leading to pallor and easy fatiguability, failure to thrive (grow), bouts of fever (due to infections) and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease.
    Mediterranean Fever: See Familial Mediterranean Fever.
    Medulla: The innermost part. The spinal medulla, for example, is that part of the spinal cord which is lodged within the vertebral canal.
    Medulloblastoma: A type of brain tumor.
    Mega-: Prefix meaning big, abnormally large.
    Megacolon: An abnormally enlarged colon.
    Megakaryocyte: A giant cell in the bone marrow that is the ancestor of blood platelets.
    Meibomian cyst: An inflammation of the oil gland of the eyelid. Also called a chalazian or a tarsal cyst.
    Meiosis: What chromosomes do during germ cell formation to halve the chromosome number from 46 to 23.
    Meiotic: Pertaining to meiosis.
    Meiotic nondisjunction: Failure of two memberrs of a chromosome pair to separate (disjoin) during meiosis so that both go to one daughter cell and none to the other. This mechanism is responsible for the extra chromosome 21 in trisomy 21 (Down syndrome) and for extra and missing chromosomes causing other birth defects and many spontaneous abortions (miscarriages).
    Melan-: Prefix meaning dark or black.
    Melancholia: Old term for depression.
    Melanin: A skin pigment (substance that gives the skin its color). Dark-skinned people have more melanin than light-skinned people.
    Melanocytes: Cells in the skin that produce and contain the pigment called melanin.
    Melanoma: Cancer of the cells that produce pigment in the skin. Melanoma usually begins in a mole.
    Melena: Stools or vomit stained black by blood pigment or dark blood products.
    Membrane: A very thin layer of tissue that covers a surface.
    Menarche: The time in a girl's life that menstruation first begins. Therefore, the opposite of the menopause.
    Mendelian: Referring to the Austrian monk Gregor Mendel (1822-84) who formulated laws forming the foundation of classical genetics.
    Meninges: The three membranes that cover the brain and spinal cord.
    Meningioma: A type of brain tumor.
    Meningocele (MM): : Protrusion of the membranes that cover the spine and part of the spinal cord through a bone defect in the vertebral column. MM is due to failure of closure during embryonic life of bottom end of the neural tube, the structure which gives rise to the central nervous system (the brain and spinal cord). The term spina bifida refers specifically to the bony defect in the vertebral column through which the meningeal membrane and cord may protrude (spina bifida cystica) or may not protrude so that the defect remains hidden, covered by skin (spina bifida occulta). However, through usage the term spina bifida is gradually becoming synonymous with MM. The risk of MM (and all neural tube defects) can be decreased by the mother eating ample folic acid during pregnancy.
    Meningomyelocele: Protrusion of the membranes that cover the spine but some of the spinal cord itself through a defect in the bony encasement of the vertebral column. The bony defect is spina bifida.
    Menometorrhagia: Excessive uterine bleeding both at the usual time of menstrial periods and at other irregular intervals.
    Menopause: The time of a woman's life when menstrual periods permanently stop; also called "change of life." Menopause is the opposite of the menarche.
    Menorrhagia: Excessive uterine bleeding at the regular menstrual times lasting longer than usual.
    Menstrual cycle: The hormone changes that lead up to a period (menstruation). For most women, one cycle takes up to 28 days.
    Menstruation: The periodic blood that flows as a discharge from the uterus. Also called menorrhea, the time during which menstruation occurs is referred to as menses. The menses occurs at approximately 4 week intervals to compose the menstrual cycle.
    Mesentery: A fold of tissue which attaches organs to the body wall. Unqualified, usually refers to the small bowel mesentery which anchors the small intestines to the back of the abdominal wall. Blood vessels, nerves, and lymphatics branch through the mesentery to supply the intestine. Other mesenteries exist to support the sigmoid colon, appendix, transverse colon, and portions of the ascending and descending colon.
    Messenger RNA (mRNA): An RNA that acts as a messenger, an intermediary, between DNA and protein. The DNA of the gene is transcribed into mRNA which then is translated into the sequence of amino acids that make up protein.
    Metabolic rate, basal: A measure of the rate of metabolism. For example, someone with an overly active thyroid will have an elevated basal metabolic rate.
    Metabolism: The whole range of biochemical processes that occur within us (or any living organism). Metabolism consists both of anabolism and catabolism (the buildup and breakdown of substances, respectively).
    Metacarpals: Five cylindrical bones extending from the wrist to the fingers.
    Metacentric: A chromosome with arms of equal length.
    Metaphase: Stage in the cell when the chromosomes are most condensed and easiest to study.
    Metastasis: The spread of cancer from one part of the body to another. Cells that have metastasized are like those in the original (primary) tumor.
    Metastasize: The spread from one part of the body to another. When cancer cells metastasize and cause secondary tumors, the cells in the metastatic tumor are like those in the original cancer.
    Metatarsals: Five cylindrical bones extending from the heel to the toes.
    Methemoglobin: Hemoglobin in a form incapable of carrying oxygen.
    Metorrhagia: Uterine bleeding at irregular intervals.
    Meuse fever: The area around the Meuse River was one of the great battlegrounds of World War I during which this louse-borne disease was first recognized in the trenches (called trench fever), again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Also called Wolhynia fever, shin bone fever, quintan fever, five-day fever, His’ disease, His-Werner disease, Werner-His disease.
    MHC: See major histocompatability complex.
    MI: Stands for myocardial infarction, a heart attack.
    Micro-: Prefix from the Greek mikros meaning small. The opposite of macro-.
    Microbe: A minute organism including bacteria, fungi, and protozoan parasites best visualized with a microscope.
    Microcephaly: An abnormally small head. Often associated with developmental delay and mental retardation.
    Microdeletion: Loss of a piece from a chromosome that is too small to be seen through a microscope. Microdeletions require high-resolution chromosome banding, molecular chromosome analysis (with FISH), or DNA analysis for detection. Disorders caused by microdeletions include Angelman, DiGeorge, Prader-Willi, and Williams syndromes.
    Microscope: An optical instrument that augments the power of the eye to see small objects. The name microscope was coined by Johannes Faber (1574-1629) who in 1628 borrowed from the Greek to combined micro-, small with skopein, to view. Although the first microscopes were simple microscopes, most (if not all) optical microscopes today are compound microscopes.
    Microscope, compound: A microscope that consists of two microscopes in series, the first serving as the ocular lens (close to the eye) and the second serving as the objective lens (close to the object to be viewed). Credit for creating the compound microscope goes usually to the Dutch spectaclemakers Hans and Zacharias Janssen who in 1590 invented an instrument that could be used as either a microscope or telescope. The compound microscope evolved into the dominant type of optical microscope today.
    Microscope, electron (EM): A microscope in which an electron beam replaces light to form the image. EM has its pluses (greater magnification and resolution than optical microscopes) and minuses (you are not really "seeing" objects, but rather their electron densities, and artefacts may abound). EM has greatly extended the powers of the microscope, although EM also has its own set of limitations.
    Microscope, fluorescent: A microscope equipped to examine material that fluoresces under ultraviolet (UV) light.
    Microscope, simple: A microscope that has a single converging lens (or a combination of lenses that function optically as a single converging lens). Anton van Leeuwenhoek (1632-1723) made good use of the simple microscope to look at the life within a drop of water, and such. The magnifying properties of lenses had been well known in ancient times (for example to the Greeks and Romans) but it was not until about 1600 that it became possible to make small lenses with the precision needed to make a microscope.
    Microscopic: So small it cannot be seen without the aid of microscope. As opposed to macroscopic (large enough to be seen with naked eye). A tiny tumor is microscopic while a big tumor is macrocopic.
    Microsomia: Too small a body. A child with microsomia has significant undergrowth.
    Micturition: To urinate.
    Midwife: A person who assists a woman during childbirth. Historically, a midwife could be a man or woman and be an obstetrician. Today, a midwife is a nurse-midwife.
    Migraine: Periodic attacks of headaches usually on one side of the head that may be accompanied by nausea, vomiting, increased sensitivity of the eyes to light and other symptoms.
    Migraine, classic: Migraine with aura. Accounts for no more than most 20% of migraines. See Migraine.
    Migraine, common: Migraine without aura. The most frequent type, accounting for about 80-85% of migraines. See Migraine.
    Migraine headache: The most common type of vascular headache involving (it is thought). abnormal sensitivity of blood vessels (arteries) in the brain to various triggers resulting in rapid changes in the artery size due to spasm (constriction). Other arteries in the brain and scalp then open (dilate), and throbbing pain is perceived in the head. The tendency to migraine is inherited and appears to involve serotonin, a chemical in the brain involved in the transmission of nerve impulses that trigger the release of substances in the blood vessels that in turn cause the pain of the migraine. These nerve impulses cause the flashing lights and other sensory phenomena known as an aura that may accompany a migraine. Not all severe headaches are migraines and not all migraines are severe.
    Milzbrand: Known also as anthrax, milzbrand is a serious bacterial infection. It is not primarily a human disease but rather an infection of animals. Cattle, sheep, horses, mules, and some wild animals are highly susceptible. Humans (and swine) are generally resistant to anthrax. Anthrax can take different forms. With the lung form of the disease. People inhale the anthrax spores and, if untreated, are likely to die. An intestinal form is caused by eating meat contaminated with anthrax. But most human anthrax comes from skin contact with animal products. Cutaneous (skin) anthrax was once well known among people who handled infected animals, like farmers, woolsorters, tanners, brushmakers and carpetmakers in the days when the brushes and carpets were animal products. The hallmark of skin anthrax is a carbuncle, a cluster of boils, that ulcerates in an ugly way. Typically this lesion has a hard black center surrounded by bright red inflammation. This accounts for its name, "anthrax", the Greek word for "coal". "Milzbrand" means "anthrax" in German.
    Mineralocorticoids: A group of hormones (the most important being aldosterone) that regulate the balance of water and electrolytes (ions such as sodium and potassium) in the body. The mineralocorticoid hormones act on the kidney (and specifically on the tubules of the kidney).
    Monoarticular: Involving just one joint. As opposed to polyarticular (affecting many joints). From the Latin "articulus," meaning a joint.
    Minor salivary gland: A small gland which produces saliva. There are numerous minor salivary glands distributed within the mouth and palate.
    Miosis: Contraction of the pupil. The opposite of mydriasis.
    Miscarriage: Inadvertant loss of a pregnancy before the fetus is viable. A considerable proportion of pregnancies end in miscarriage. Also called a spontaneous abortion.
    Miscarriages, multiple, chromosomes in: Couples who have had more than one miscarriage have about a 5% chance that one member of the couple is carrying a chromsome translocation responsible for the miscarriages.
    Missense mutation: A genetic change that results in the substitution of one amino acid in protein for another. A missense mutation is responsible for sickle hemoglobin, the molecular basis of sickle cell trait and sickle cell anemia.
    Mite-borne typhus: Scrub: typhus, a mite-borne infectious disease caused by a microorganism, Rickettsia tsutsugamushi, characteristically with fever, headache, a raised (macular) rash, swollen glands (lymphadenopathy) and a dark crusted ulcer (called an eschar or tache noire) at the site of the chigger (mite larva) bite. This disease occurs in the area bounded by Japan, India, and Australia. Known also as Tsutsugamushi disease and tropical typhus.
    Mitochondria: Normal structures in cells. Mitochondria are located in the cell's cytoplasm outside the nucleus (which is home to the normal human complement of 46 chromosomes). Each mitochondrion has a chromosome made of DNA but, otherwise, the mitochondrial chromosome is quite different in size and shape from other chromosomes: The mitochondrial chromosome is much smaller, it is round (whereas the chromosomes in the nucleus are shaped like rods) and there are many copies of the mitochondrial chromosome per cell. No matter whether we are male or female, we all inherit our mitochondrial chromosome from our mother so we all owe our mitochondrial chromosomes to Eve (rather than to Adam).
    Mitochondrial: Referring to mitochondria.
    Mitochondrial disease: Mutations (changes) in the mitochondrial chromosome are responsible for a number of disorders including an eye disease (Leber's hereditary optic atrophy), a type of epilepsy (called MERRF which stands for Myoclonus Epilepsy with Ragged Red Fibers), and a cause of dementia (called MELAS for Mitochondrial Encephalopathy, Lactic Acidosis and Stroke-like episodes). All mitochondrial diseases were entirely enigmatic before it was discovered that they were due to mutations not in regular chromosomes but the mitochondrial chromosome..
    Mitochondrial genome: All of the DNA in the mitochondrial chromosome.
    Mitochondrial inheritance: The inheritance of a trait encoded in the mitochondrial genome. Because of the oddities of mitochondria, mitochondrial inheritance does not obey the classic rules of genetics. Persons with a mitochondrial disease may be male or female but they are always related in the maternal line and no male with the disease can transmit it to his children.
    Mitochondrion: Singular of mitochondria. (See mitochondria).
    Mitosis: Ordinary division of a body cell to form two daughter cells each with the same chromosome complement as the parent cell.
    Mitotic: Pertaining to mitosis.
    Mitotic nondisjunction: Failure of the two members of a chromosome pair to separate (disjoin) during mitosis so that both go to one daughter cell and none to the other.
    Mitral insufficiency: Malfunction of the mitral valve. Mitral insufficiency allows the backflow of blood (regurgitation) from the left ventricle into the left atrium.
    Mitral prolapse: Drooping down or abnormal bulging of the mitral valve cusps during the contraction of the heart.
    Mitral regurgitation: Backflow of blood from the left ventricle to the left atrium due to mitral valve insufficiency (malfunction).
    Mitral valve: Heart valve with two cusps situated between the left atrium and ventricle. Called mitral because it looks like a bishop's miter or headdress.
    Mittelschmerz: Pain in between the menstrual periods. From the German mittel for middle and schmerz for pain.
    MM: Meningomyelocele.
    MMR: Measles, mumps, rubella vaccine.
    Molar: In dentistry, a molar is one of the posterior teeth well adapted to grinding, in keeping with its origin from the Latin mola meaning millstone.
    Molars: Molars are the large teeth at the back of the mouth.
    Mold: A large group of fungi (like Penicillium) that cause mold (as on bread or cheese). A common trigger for allergies.
    Mole: 1. A pigmented spot on the skin (nevus). 2. A mass within the uterus (womb) formed by partly developed products of conception.
    Molecule: The smallest unit of a substance that can exist alone and retain the character of that substance.
    Molecules, recombinant DNA: A combination of DNA molecules of different origin that are joined using recombinant DNA technology.
    Mongolism: See Down syndrome.
    Monilia: A yeast-like fungus now called Candida.
    Monitor, Holter: A technique for long-term, continuous cardiac surveillance. A cassette tape is worn by the patient continuously while carrying out his/her usual activities. The patient simultaneously keeps a diary of palpitations or other symptoms during the recording period. Symptoms of palpitations can later be correlated with the presence or absence of arrhythmias (abnormal heart rhythms) on the Holter tape. The recordings can be analyzed by a doctor at a later date. Named for the late American biophysicist Norman Holter.
    Mono: Popular name for infectious mononucleosis.
    Monoclonal: Derived from a single cell and cells identical to that cell.
    Monoclonal antibodies: Identical antibodies that are made in large amounts in the laboratory. Doctors are studying ways of using monoclonal antibodies to treat leukemia.
    Monocyte: A white blood cell that has a single nucleus and can take in (ingest) foreign material.
    Mononucleosis: See infectious mononucleosis.
    Monosomy: Missing one chromosome from a pair. A female with 45 chromosomes including just one X chromosome (X monosomy) resulting in Turner syndrome.
    Monozygous twins: Identical twins. Called monozygous because they originate from a single fertilized egg (a zygote).
    Morbidity: Illness, disease.
    Morgue: A place where bodies of the dead are kept before funeral ceremonials. The first Morgue was in Paris. In the 1880s the word morgue entered English to mean a mortuary.
    Morphology: Literally, the study of form (structure). It is also the form itself.
    Mortality rate, fetal: The ratio of fetal deaths to the sum of the births (the live births + the fetal deaths) in that year. In the United States, the fetal mortality rate plummeted from 19.2 per 1,000 births in 1950 to 9.2 per 1,000 births in 1980.
    Mortality rate, infant: The number of children dying under a year of age divided by the number of live births that year. The infant mortality rate in the United States, which was 12.5 per 1,000 live births in 1980, fell to 9.2 per 1,000 live births in 1990.
    Mortality rate, maternal: The number of maternal deaths related to childbearing divided by the number of live births (or by the number of live births + fetal deaths) in that year. The maternal mortality rate in the United States in 1993 (and 1994) was 0.1 per 1,000 live births, or 1 mother dying per 10,000 live births.
    Mortality rate, neonatal: The number of children dying under 28 days of age divided by the number of live births that year. The neonatal mortality rate in the United States, which was 8.4 per 1,000 live births in 1980, declined to 5.8 per 1,000 live births in 1990.
    Mosaic: An individual or tissue containing two or more types of genetically different cells. All females are mosaics because of X-chromosome inactivation (lyonization).
    Motion, range of: The range through which a joint can be moved, usually its range of flexion and extension. Due to an injury, the knee may for example lack 10 degrees of full extension.
    Motor: Something that produces or refers to motion. For example, a motor neuron is a nerve cell that conveys an impulse to muscle for contraction, which moves a joint.
    M.P.H.: Master of Public Health (master’s degree in this area of medicine).
    MRC: The Medical Research Council (U.K.).
    MRI: A procedure using a magnet linked to a computer to create pictures of areas inside the body. MRI stands for magnetic resonance imaging.
    mRNA: See messenger RNA.
    MS: Multiple sclerosis.
    MSAFP: Abbreviation for maternal serum alpha-fetoprotein.
    Mucosa: Having to do with a mucous membrane. For example, the oral mucosa.
    Mucoviscidosis: An old name (but one that has prevailed in France and some other nations) for cystic fibrosis (CF), one of the most common and serious of all genetic (inherited) diseases. The CF gene is carried by 1/20 persons (in Caucasian populations) and 1 in 400 couples is at risk for having children with CF. CF is characterized by the production of abnormal secretions leading to mucous build-up. which can impair the pancreas (and, secondarily, the intestine). CF mucous build-up in lungs can impair respiration. Without treatment, CF results in death for 95% of children before age 5. Early diagnosis of CF is of great importance. Early and continuing treatment of CF is valuable.
    Mucocutaneous lymph node syndrome: A syndrome of unknown origin, mainly affecting young children, causing fever, reddening of the eyes (conjunctivitis), lips and mucous membranes of the mouth, ulcerative gum disease (gingivitis), swollen glands in the neck (cervical lymphadenopathy), and a rash that is raised and bright red (maculoerythematous) in a glove-and-sock fashion over the skin of the hands and feet which becomes hard, swollen (edematous), and peels off. Also called Kawasaki’s disease.
    Mucus: A thick fluid produced by the lining of some organs of the body.
    Mucus colitis: A common gastrointestinal disorder characterized by abdominal pain, bloating, mucous in stools, and irregular bowel habits with alternating diarrhea and constipation, symptoms that tend to be chronic and wax and wane over the years. Although mucus colitis can cause chronic recurrent discomfort, it appears to be an abnormal condition of gut contractions (motility) and does not lead to any serious organ problems. Diagnosis usually involves excluding other illnesses. Treatment is directed toward relief of symptoms and includes high fiber diet, exercise, relaxation techniques, avoidance of caffeine, milk products and sweeteners, and medications. Alternative names include irritable bowel syndrome, spastic colitis and nervous colon syndrome.
    Multifactorial: Referring to multiple factors.
    Multifactorial inheritance: Type of hereditary pattern seen with a combination of genetic factors, sometimes with environmental influence. Skin color, for example, is multifactorially determined.
    Multi-Infarct Dementia: Dementia brought on by a series of strokes.
    Multipara: A woman who has had 2 or more pregnancies resulting in potentially viable offspring. A woman who is "para III" has had 3 such pregnancies. A woman who is "para VI" or more is called a grand multipara.
    Multiple myeloma: A malignancy of plasma cells (a form of lymphocyte) that typically involves multiple sites within the bone morrow and secretes all or part of a monoclonal antibody . Also called plasma cell myeloma.
    Multiple sclerosis (MS): The National Multiple Sclerosis Society says of MS that it is "a disease that randomly attacks your central nervous system, wearing away the control you have over your body. Symptoms may range from numbness to paralysis and blindness. The progress, severity and specific symptoms cannot be foreseen. You never know when attacks will occur, how long they will last, or how severe they will be. Most people are diagnosed with MS between the ages of 20 and 40...." In medical terms, MS involves demyelinization of the white matter sometimes extending into the gray matter. Demyelinization is loss of myelin, the coating of nerve fibers composed of lipids (fats) and protein that serves as insulation and permits efficient nerve fiber conduction. The "white matter" is the part of the brain which contains myelinated nerve fibers and appears white, whereas the gray matter is the cortex of the brain which contains nerve cell bodies and appears gray. When myelin is damaged in MS, nerve fiber conduction is faulty or absent. Impaired bodily functions or altered sensations associated with those demyelinated nerve fibers give rise to the symptoms of MS. Recent research (1998) has also identified nerve cell death as part of the nervous system injury in MS.
    Mumps: An acute (sudden and shortlived) viral illness, mumps usually presents with inflammation of the salivary glands, particularly the parotid glands. A child with mumps often looks like a chipmunk with a full mouth due to the swelling of the child's parotids (salivary glands near the ears). Mumps can also cause inflammation of other tissues, most frequently the covering and substance of the central nervous system (meningoencephalitis), next the pancreas (pancreatitis) and, especially after adolescence, the ovary (oophoritis) and the testis (orchitis). The mature testis is particularly susceptible to damage from mumps which can lead to infertility. Together with the likes of measles and chickenpox, mumps was once considered one of the inevitable infectious diseases of childhood. Since a mumps vaccine became available in 1967, the incidence of mumps has declined in the U.S., but there are still many underimmunized populations (for example, more blacks than whites have not yet been immunized). The origin of the word mumps is not clear. It may have to do with the English usage, now obsolete, of "mump" to mean a grimace. More probably, mumps comes from a colder climate, Iceland, where mumpa meant to fill the mouth too full.
    Mumps immunization: The standard MMR vaccine is given to prevent measles, mumps and rubella (German measles). The MMR vaccine is now given in two dosages. The first should be given at12-15 months of age. The second vaccination should be given at 4-6 years (or, alternatively, 11-12 years) of age. Most colleges require proof of a second measles or MMR vaccination prior to entrance. Most children should receive MMR vaccinations. Exceptions may include children born with an inability to fight off infection, some children with cancer, on treatment with radiation or drugs for cancer, on long term steroids (cortisone). People with severe allergic reactions to eggs or the drug neomycin should probably avoid the MMR vaccine. Pregnant women should wait until after delivery before being immunized with MMR. People with HIV or AIDS should normally receive MMR vaccine. Measles, mumps, and rubella vaccines may be administered as individual shots, if necessary, or as a measles-rubella combination.
    Mumps in pregnancy: It has been stated, we believe erroneously, that mumps is dangerous when contracted during pregnancy. For example, Vetter (Infect Med 14:730-733, 1997), citing a single 1980 article, writes: "Mumps infection during the first trimester of pregnancy can increase the rate of spontaneous abortion. Congenital anomalies associated with mumps infection during pregnancy include endocardial fibroelastosis; imperforate anus; spina bifida; and auditory, optic, and urogenital deformities." However, Shepard in his authorative Catalog of Teratogenic Agents (J Hopkins U Press, 8th edition, 1995) does not consider that mumps merits inclusion as a proven or even possible teratogenic agent, that is as an agent capable of causing a spontaneous abortion (a miscarriage) or causing congenital malformations (the baby is born with birth defects). Furthermore, mumps does not even warrant mention in Smith's Recognizable Patterns of Human Malformation (by KL Jones, WB Saunders Co., 5th edition, 1997), a key standard text on dysmorphology (the study of malformations). Based also on our review of the facts available at this time (Oct, 1997), we conclude that there is insufficient evidence to label mumps as a particular hazard in pregnancy.
    Munchhausen syndrome: Recurrent feigning of catastrophic illnesses. Named for the fictitious Baron who told tales that were whopping lies.
    Murine typhus: An acute infectious disease with fever, headache, and rash, all quite similar to, but milder than, epidemic typhus, caused by a related microoganism, Rickettsia typhi (mooseri), transmitted to humans by rat fleas (Xenopsylla cheopis). The animal reservoir includes rats, mice and other rodents. Murine typhus occurs sporadically worldwide but is more prevalent in congested rat-infested urban areas. Also known as endemic typhus, rat-flea typhus; urban typhus of Malaya).
    Murmur: A Murmur is an abnormal "whooshing" sound created by blood flow through heart valves, as well as flow through chamber narrowings or unusual connections seen with congenital heart disease. It is usually heard by the doctor while listening to the chest with a stethoscope.
    Muscle: Muscle is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart muscle is called "cardiac muscle." Muscle that is in the walls of arteries and bowel is called "smooth muscle."
    Muscle, adductor: Any muscle that pulls inward toward the midline of the body. For example, the adductor muscles of the leg serve to pull the legs together. The opposite of "adductor" is "abductor." To keep these similar sounding terms straight, medical students learn to speak of "A B ductors" versus "A D ductors."
    Muscle, central core disease of (CCD): One of the conditions that produces ‘floppy baby’ syndrome. CCD causes hypotonia (inadequately toned muscles characterized by floppiness) in the newborn baby, slowly progressive muscle weakness, and muscle cramps after exercise. Muscle biopsy shows a key diagnostic finding (absent mitochondria in the center of many type I muscle fibers). CCD is inherited as a dominant trait. The CCD gene is on chromosome 19 (and involves ryanodine receptor-1).
    Muscular: Having to do with the muscles. Also, endowed with above average muscle development. Muscular system refers to all of the muscles of the body collectively.
    Mutagen: Something capable of causing a gene-change. Among the known mutagens are radiation, certain chemicals and some viruses.
    Mutant: An individual with a mutant (changed) gene.
    Mutation: A gene-change.
    Myalgia: Pain in muscles. The Greek "algos" means "pain."
    Myasthenia gravis: A nerve-muscle (neuromuscular) disorder with fatigue and exhaustion of muscles.
    Mycoplasma: A group of bacteria. A common cause of pneumonia in persons with HIV.
    Mycosis fungoides: A type of non-Hodgkin's lymphoma that first appears on the skin. Also called cutaneous T-cell lymphoma.
    Mydriasis: Dilation of the pupils induced by eyedrops. The opposite of miosis.
    Myelin: The fatty substance that covers and protects nerves. Myelin is a layered tissue surrounding the axons or nerve fibers. The sheath around the nerve fibers which acts electrically as a conduit.
    Myelitis: Inflammation of the spinal cord.
    Myelodysplastic syndrome: A condition in which the bone marrow does not function normally. It does not produce enough blood cells. This condition may progress and become acute leukemia. Myelodysplastic syndrome also is called preleukemia or smoldering leukemia.
    Myelofibrosis: Fibrosis (spontaneous scarring) of the bone marrow. This can be associated with a variety of diseases, primarily myeloproliferative (pre-leukemic) disorders. Sometimes used interchangeably with agnogenic myeloid metaplasia. Acute myelofibrosis: a distinct disorder characterized by acute inadequate blood cell production (pancytopenia), marrow fibrosis, but no enlargement of the spleen or liver.
    Myelogenous: Referring to myelocytes, a type of white blood cell. Also called myeloid.
    Myelogram: An x-ray of the spinal cord and the bones of the spine.
    Myeloid: Referring to myelocytes, a type of white blood cells. Also called myelogenous.
    Myeloma: A tumor of cells that are normally found in the bone marrow.
    Myeloproliferative disorders: Tumors of certain bone marrow cells including those that give rise to red cells, granulocytes, and platelets. As opposed to the lymphoproliferative disorders.
    Myocarditis: Inflammation of the heart muscle.
    Myocardium: The heart muscle.
    Myoclonus: Shock-like contraction of muscle.
    Myoglobin: The pigment in muscle that carries oxygen.
    Myoma: A tumor of muscle. Can specifically refer to a benign tumor of uterine muscle, also called a leiomyoma or a fibroid.
    Myometrium: The muscular outer layer of the uterus.
    Myopathy: Any and all disease of muscle.
    Myopia: Nearsightedness.
    Myotonic dystrophy: Inherited disease with myotonia (irritability and prolonged contraction of muscles), mask-like face, premature balding, cataracts, and cardiac disease. Due to a trinucleotide repeat (a stuttering sequence of three bases) in the DNA.
    Myringotomy: Draining of fluid by making an opening in the middle ear, for example, in which to put ear tubes.

  • Na: The chemical symbol for sodium. From natrium, a synonym for sodium. Sodium chloride (ordinary salt) is NaCl.
    Nail: In medicine, there are two types of nails. One is just a plain old metal nail used to hold 2 or more pieces of bone together, for example, after a fracture. The other type of nail is the horny plate on the end of the finger or toe. Each nail anatomically has a body, lateral nail folds (on the sides), a lunula (the little moon-shaped feature at the base), and a proximal skin fold (at the base).
    Nail infection, fungal: The most common fungus infection of the nails is onychomycosis. Onychomycosis makes the nails look white and opaque, thickened, and brittle. Older women (perhaps because estrogen deficiency may increase the risk of infection). and men and women with diabetes or disease of the small blood vessels (peripheral vacscular disease) are at increased risk. Artificial nails (acrylic or "wraps") increase the risk because when an artificial nail is applied, the nail surface is usually abraded with an emery board damaging it, emery boards can carry infection, and. water can collect under the nail creating a moist, warm environment for fungal growth. Alternative names include tinea unguium and ringworm of the nails.
    Nails, ringworm of the: See Nail infection, fungal.
    Nail-patella syndrome: An hereditary condition with abnormally formed (dysplastic) or absent nails and absent or underdeveloped (hypoplastic) kneecaps (patellae). Other features include iliac horns, abnormality of the elbows interfering with full range of motion (pronation and supination) and kidney disease resembling glomerulonephritis which.is often mild but can be progressive and lead to renal failure. Nail-patella syndrome is inherited as dominant gene. This means that the disease can be transmitted by one affected parent. The nail-patella gene locus found linked genetically to the ABO blood group in 1965 is now known to be in chromosome region 9q34. Also called Turner-Kieser syndrome, and Fong disease.
    Named reporting: In public health, named reporting is the reporting of infected persons by name to public health departments. This is standard practice for the surveillance of many infectious diseases such as syphilis, gonorrhea, and tuberculosis that pose a public health threat. The opposite of named reporting is anonymous testing in which the individual remains nameless.
    Nanism: Once known as dwarfism, this condition is now correctly called short stature.
    Nares: The nostrils. The word "nares" is straight out of Latin (still another reason why you should have taken Latin in school or, if you did, studied harder).
    Nasal: Having to do with the nose. Nasal drops are intended for the nose, not (for example) the eyes. The word "nasal" came from the Latin "nasus" meaning the nose or snout.
    Nasal decongestants: Drugs that shrink the swollen membranes in the nose and make it easier to breath. Decongestants can be taken orally or by nasal spray. Decongestant nasal spray should not be used for more than five days without the doctor"s advice, and if so, usually only when accompanied by a nasal steroid. Decongestant nasal sprays often cause a rebound effect if taken too long. A rebound effect is the worsening of symptoms when a drug is discontinued. This is a result of a tissue dependence on the medication.
    Nasal septum: The dividing wall that runs down the middle of the nose so that there are normally two sides to the nose, each ending in a nostril.
    Nasopharynx: The area of the upper throat behind the nose.
    Naturopath: A person who practices naturopathy, a drugless system of therapy based on the use of physical forces such as heat, water, light, air and Messages.
    Navel: The umbilicus. The word navel came from the Anglo-Saxon nafe for the hub of a wheel.
    Nausea: Nausea is the urge to vomit. It can be brought by many causes including, systemic illnesses, such as influenza, medications, pain, and inner ear disease.
    Neck dissection: Surgery to remove lymph nodes and other tissues in the neck.
    Neck, wry: Medically called spasmodic torticollis, or torticollis. The most common of the focal dystonias. In torticollis, the muscles in the neck that control the position of the head are affected, causing the head to twist and turn to one side. In addition, the head may be pulled forward or backward.
    Necropsy: A postmortem examination.
    Necrosis: Death of cells or tissues. Necrosis can be due for example to ischemia (lack of blood flow).
    Necrotic: Synonymous with dead. Necrotic tissue is dead tissue.
    Neisseria: Group of bacteria that includes the cause of gonorrhea.
    Nematodes: Roundworms.
    Neo-: Prefix meaning new.
    Neonatal: Pertaining to the newborn period which, by convention, is the first 4 weeks after birth.
    Neonatal mortality rate: The number of children dying under 28 days of age divided by the number of live births that year. The neonatal mortality rate in the United States, which was 8.4 per 1,000 live births in 1980, declined to 5.8 per 1,000 live births in 1990.
    Neonate: A newborn baby.
    Neonatologist: A specialist in the care of the newborn.
    Neonatology: The art and science of caring medically for the newborn.
    Neoplasia: Abnormal new growth of cells.
    Neoplasm: Literally, a new growth. Neoplasm is another word for a tumor.
    Nephrectomy: Surgery to remove the kidney. Radical nephrectomy removed the kidney, the adrenal gland, nearby lymph nodes, and other surrounding tissue. Simple nephrectomy removes just the affected kidney. Partial nephrectomy removes the tumor, but not the entire kidney.
    Nephritis: Inflammation of the kidney.
    Nephro-: Having to do with the kidney. From the Greek nephros meaning kidney.
    Nephrologist: A medical specialist in nephrology (the study of the kidney or "kidney-ology").
    Nephrology: The art and science of the care of the kidney.
    Nephron: A key unit, both anatomically and functionally, of the kidney.
    Nephrosclerosis: Hardening (sclerosis) of the kidney usually due to disease of the blood vessels in it from atherosclerosis.
    Nephrosis: Non-inflammatory, non-neoplastic disease of the kidney.
    Nephrolithiasis: Kidney stones.
    Nephrotomogram: A series of special x-rays of the kidneys. The x-rays are taken from different angles. They show the kidneys clearly, without the shadows of the organs around them.
    Nerve: A nerve is a bundle of fibers that uses electrical and chemical signals to transmit sensory and motor information from one body part to another. (see nervous system).
    Nerve Growth Factor: A substance that occurs naturally in the body and enhances the growth and survival of cholinergic nerves.
    Nervous colon syndrome: A common gastrointestinal disorder characterized by abdominal pain, bloating, mucous in stools, and irregular bowel habits with alternating diarrhea and constipation, symptoms that tend to be chronic and wax and wane over the years. Although nervous colon syndrome can cause chronic recurrent discomfort, it appears to be an abnormal condition of gut contractions (motility) and does not lead to any serious organ problems. Diagnosis usually involves excluding other illnesses. Treatment is directed toward relief of symptoms and includes high fiber diet, exercise, relaxation techniques, avoidance of caffeine, milk products and sweeteners, and medications. Alternative names include irritable bowel syndrome, spastic colitis, and mucus colitis.
    Nervous system: The nervous system is the body tissue that records and distributes information in the body using electrical and chemical transmission. It has two parts. The "central" nervous system is comprised of the brain and spinal cord. The "peripheral" nervous system is the nerve tissue that transmits sensation and motor information back and forth from the body to the central nervous system.
    Nervous system, autonomic: Part of the nervous system once thought functionally independent of the brain. The autonomic nervous system regulates key functions including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The autonomic nervous system has two divisions: (1) the sympathetic nervous system, which accelerates the heart rate, constricts blood vessels, and raises blood pressure; and (2) the parasympathetic nervous system, which slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles.
    Nervous system, parasympathetic: A part of the nervous system that slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles. The parasympathetic nervous system together with the sympathetic nervous system (that accelerates the heart rate, constricts blood vessels, and raises blood pressure) constitute the autonomic nervous system.
    Nervous system, sympathetic: A part of the nervous system that accelerates the heart rate, constricts blood vessels, and raises blood pressure. The sympathetic nervous system together with the parasympathetic nervous system (that slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles) constitute the autonomic nervous system.
    Neural: Having to do with nerve cells.
    Neural tube defect (NTD): Abnormal development during embryonic life of the neural tube, the structure which gives rise to the central nervous system (the brain and spinal cord), resulting in anencephaly (absence of the cranial vault and absence of most or all of the cerebral hemispheres of the brain) and spina bifida/meningomyelocele (open spina with exposure and protusion of the spinal cord). The risk of NTDs can be decreased by the mother eating ample folic acid during pregnancy.
    Neuralgia: Pain along the course of a nerve. Facial neuralgia is severe pain usually occurrring in bursts from the trigeminal nerve, the chief sensory nerve of the face.
    Neuritis: Inflammation of nerves.
    Neuroblastoma: Childhood tumor of adrenal or related tissue in the nervous system.
    Neurofibromatosis (NF1): Hereditary disorder characterized by cafe-au-lait (coffee-with-milk spots on the skin and a tendency to tumors) also known as von Recklinghausen's disease.
    Neurogenic: Starting with or having to do with the nerves or the nervous system.
    Neurologist: A doctor who specializes in the diagnosis and treatment of disorders of the nervous system.
    Neuroma: A tumor that arises in nerve cells.
    Neuroma, optic: A benign tumor of the optic nerve.
    Neurosurgeon: A doctor who specializes in surgery on the brain and other parts of the nervous system.
    Neurosyphilis: The neurologic complications in the last ("tertiary") phase of syphilis involving the central nervous system.
    Neurosyphilis, tabes: Also known as tabes dorsalis, the slowly progressive degeneration of the spinal cord that occurs in the late (tertiary) phase of syphilis a decade or more after contracting the infection. Among the terrible features are lancinating lightning-like pain, ataxia (wobbliness), deterioration of the nerve to the eye (the optic nerve) leading to blindness, urinary incontinence, loss of the sense of position, and degeneration of the joints (Charcot’s joints). Tabes is the Latin word for decay. The term tabes dorsalis was devised in 1836 when the cause of the condition was thought to be wastage of the dorsal (posterior) columns of the spinal cord, well before it was recognized as part of late syphilis.
    Neurotoxic: Poisonous to nerves or nerve tissue. (example: lead)
    Neutropenia: Not enough neutrophils.
    Neutrophil: A type of white blood cell.
    Neutrophilia: Too many neutrophils.
    Nevus: A pigmented spot on the skin, such as a mole. The plural of nevus is nevi.
    Newborn screening: Tests of newborns to detect those at increased risk for disorders such as PKU (phenylketonuria) and hypothyroidism.
    NIH: The National Institutes of Health.
    Nipple: The pigmented projection on the surface of the breast. Ducts which conduct milk from milk glands to the surface of the breast exit through the nipple. The surrounding flat area of pigmentation is the areola.
    Nipple, supernumerary: An extra nipple.
    Nitrogenous base: A molecule that contains nitrogen and has the chemical properties of a base. The nitrogenous bases in DNA are adenine (A), guanine (G), thymine (T), and cytosine ©. The nitrogenous bases in RNA are the same with one exception: adenine (A), guanine (G), uracil (U), and cytosine ©
    Nitrosoureas: A group of anticancer drugs that can cross the blood-brain barrier. Carmustine (BCNU) and lomustine (CCNU) are nitrosoureas.
    NMR: Nuclear Magnetic Resonance. An imaging technique that does not use radiation.
    Nocturia: Excessive urinating at night.
    Node: Literally a knot, a node is a collection of tissue. For example a lymph node, is a collection of lymphoid tissue.
    Node, AV: Atrioventricular node. Specialized heart tissue which acts as an electrical relay station between the upper chambers of the heart (atria) and the lower chambers of the heart (ventricles). Electrical signals from the sinoatrial (SA) node and the atria must pass through the AV node to reach the ventricles.
    Node, SA: Sinoatrial node. The pacemaker of the heart, located in the right atrium (upper chamber of the heart). The electrical signals initiated in the SA node are transmitted throuhg the atria and the ventricles to stimulate heart muscle contractions (heartbeats).
    Nodular: Bumpy.
    Nodule: A small node, a bump.
    Nondisjunction: Failure of paired chromosomes to disjoin (separate) during cell division so both chromosomes go to one daughter cell and none to the other. Nondisjunction causes errors in chromosome number such as trisomy 21 (Down syndrome) and monsomy X (Turner syndrome).
    Nonmelanoma skin cancer: Skin cancer that does not involve melanocytes. Basal cell cancer and squamous cell cancer are nonmelanoma skin cancers.
    Nonseminoma: A classification of testicular cancers that arise in specialized sex cells called germ cells. Nonseminomas include embryonal carcinoma, teratoma, choriocarcinoma, and yolk sac tumor.
    Nonsense mutation: A change in a DNA that prematurely stops the eading of messenger RNA. A nonsense mutation creates a stop codon (a triplet of bases that signals stop).
    Nonsmall cell lung cancer: A general classification for squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.
    Normal range: Normal results can fall outside the normal range. By convention, the normal range is set to cover ninety-five percent (95%) of values from a normal population. Five percent (5%) of normal results therefore fall outside the normal range.
    North Asian tick-borne rickettsiosis: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.
    Northern blot: A technique in molecular biology, used mainly to separate and identify pieces of RNA. Called a Northern blot because it is similar to a Southern blot (which is named after its inventor, the British biologist M.E. Southern).
    Nosebleed: Its medical name is epistaxis.
    Nosebleed, causes of: The nose is a part of the body that is very rich in blood vessels (vascular) and is situated in a vulnerable position on the face. As a result, any trauma to the face can cause bleeding which may be profuse. Nosebleeds can occur spontaneously when the nasal membranes dry out, crust, and crack, as is common in dry climates, or during the winter months when the air is dry and warm from household heaters. People are more susceptible if they are taking medications which prevent normal blood clotting (coumadin, warfarin, aspirin, or any anti-inflammatory medication). Other predisposing factors include infection, trauma, allergic and non-allergic rhinitis, hypertension., alcohol abuse and inherited bleeding problems.
    Nosebleed, treatment of: To stop a nosebleed, you should: 1. Pinch all the soft parts of the nose together between your thumb and index finger. 2. Press firmly toward the face - compressing the pinched parts of the nose against the bones of the face. 3. Hold the nose for at least 5 minutes (timed by the clock). Repeat as necessary until the nose has stopped bleeding. 4. Sit quietly, keeping the head higher than the level of the heart; that is, sit up or lie with the head elevated. Do not lay flat or put your head between your legs. 5. Apply ice (crushed in a plastic bag or washcloth) to nose and cheeks.
    Nose job: Plastic surgery on the nose known medically as a rhinoplasty.
    Nose, runny: Rhinorrhea is the medical term for this common problem. From the Greek words "rhinos" meaning "of the nose" and "rhoia" meaning "a flowing."
    Nosocomial: Hospital-acquired. A nosocomial infection is one contracted in the hospital.
    NSAIDS: Abbreviation for nonsteroidal anti-inflammatory drugs. This is a large group of medications used to treat conditions associated with inflammation.
    NTD: Neural tube defect.
    Nucleic acid: DNA or RNA.
    Nucleosome: Structure responsible in part for the compactness of a chromosome. Each nucleosome consists of a sequence of DNA wrapped around a core of histone (a type of protein).
    Nucleotide: A subunit of DNA or RNA. A nucleotide consists of a nitrogenous base (A, G, T, or C in DNA; A, G, U, or C in RNA), a phosphate molecule, and a sugar molecule (deoxyribose in DNA and ribose in RNA). Thousands of nucleotides are linked to form a DNA or RNA molecule.
    Nucleus: In cell biology, the structure that houses the chromosomes. In neuroanatomy, a group of nerve cells.
    Nullipara: A woman who has not given birth to a viable child.
    Null mutation: Change in a gene that leads to nothing, for example to no enzyme or to a nonfunctioning enzyme.
    Nurse: A person skilled in nursing. Also, to feed at the breast (suckle) as an infant.
    Nursing: Profession (better known than defined) concerned with the provision of services essential to the maintenance and restoration of health by attending the needs of sick persons. Also, feeding a infant at the breast.
    Nutrition: The science of taking in and utilizing foods.
    Nutritionist: A specialist in nutrition.
    Nystagmus: Rapid rhythmic repetitious involuntary (unwilled) eye movements. Nystagmus can be horizontal, vertical or rotary.

  • Oat cell cancer: A type of lung cancer in which the cells look like oats. Also called small cell lung cancer. 
    OB: Short for obstetrics (or an obstetrician).
    Obesity: Overweight. Please see MedicineNet site on OBESITY for more information.
    OB/GYN: A commonly used abbreviation. GYN is short for gynecology (or a gynecologist).
    Obsessive-compulsive: A form of personality (or personality disorder) marked by obsessions and compulsions.
    Obstetrician: A physician who delivers babies and is in the practice of obstetrics.
    Obstetrics: The art and science of managing pregnancy, labor and the pueperium (the time after delivery).
    Obtunded: Mentally dulled. Head trauma may obtund a person.
    Occipital bone: The bone forming the rear (and rear bottom) of the skull.
    Occiput: The back of the head.
    Occular: Having to do with the eye.
    Occult: Hidden. Occult blood is hidden from the eye but is nontheless present and can be detected by chemical tests.
    OCP: Oral contraceptive pill. Also known as "the pill".
    Ocular: Having to do with the eye.
    Oesophagus: Alternate spelling for esophagus.
    Ointment: An ointment has an oil base whereas a cream is water-soluble. (The word ointment comes from the Latin ungere meaning anoint with oil).
    Olfaction: The sense of smell. Olfactory apparatus: The whole system needed to have a sense of smell.
    Oligo-: Means just a few or scanty.
    Oligodendroglioma: A type of brain tumor.
    Oligohydramnios: Scant amniotic fluid: less than usual.
    Oligomenorrhea: Scant menstruation. Less menstrual blood flow than usual.
    Oligospermia: Fewer sperm than usual. Azospermia, by contrast, means absolutely no sperm at all.
    Oliguria: Less urination than normal.
    Oligonucleotide: A short DNA molecule composed of relatively few nucleotide bases.
    Omentum: A sheet of fat covered by peritoneum. The greater omentum is attached to the bottom edge of the stomach and hangs down in front of the intestines. The other edge is attached to the transverse colon. The lesser omentum is attached to the top edge of the stomach and extends to the undersurface of the liver.
    Colon - add the following to the end of the existing text: The colon can be divided into ascending (right), transverse, descending (left), and sigmoid segments. The ascending colon includes the cecum which joins with the small bowel and also has the appendix attached to it. Stool then proceeds up the ascending colon toward the liver, then across to the left side of the body via the transverse colon. Near the spleen, the colon turns downward and becomes the descending colon which becomes the sigmoid colon toward the pelvis.
    Ommaya reservoir: A device implanted under the scalp and used to deliver anticancer drugs to the fluid surrounding the brain and spinal cord.
    Omphalocele: A birth defect with intestine protruding outside the abdomen at the umbilicus. Due to a failure at 10 weeks' embryonic development for the intestine, for a time normally outside the abdomen, to return.
    Oncogene: A gene that plays a normal role in cell growth and, when altered, may contribute to the growth of a tumor. The word oncogene (literally, cancer gene) is catchy but oversimplifies the complex process of cancer.
    Oncologist: A doctor who specializes in treating cancer.
    Onycho-: Having to do with the nails.
    Onychodystrophy: Malformation of the nails. Oo-: Prefix meaning egg. Pronounced o'-o.
    Onychoosteodysplasia: The nail-patella syndrome, an hereditary condition with abnormally formed (dysplastic) or absent nails and absent or underdeveloped (hypoplastic) kneecaps (patellae). Other features include iliac horns, abnormality of the elbows interfering with full range of motion (pronation and supination) and kidney disease resembling glomerulonephritis which.is often mild but can be progressive and lead to renal failure. Onychoosteodysplasia is inherited as dominant gene. This means that the disease can be transmitted by one affected parent. The nail-patella gene locus found linked genetically to the ABO blood group in1965 is now known to be in chromosome region 9q34. Also called Turner-Kieser syndrome, and Fong disease.
    Oocyte: A female germ cell in the works; a developing egg cell.
    Oogonium: Ancestral cell that gives rise to oocytes.
    Oophorectomy: The removal of one or both ovaries. Oophoritis: Inflammation of the ovary.
    Open reading frame: (genetics) An open reading frame in DNA has no termination codon, no signal to stop reading the nucleotide sequence, and so may be translated into protein.
    Ophthalmoscope: A lighted instrument used to examine the inside of the eye, including the retina and the optic nerve.
    Ophthalmia: Inflammation of the eye.
    Ophthalmic: Pertaining to the eye. An ophthalmic ointment is designed for the eye.
    Ophthalmologist: An eye doctor. A physician practicing ophthalmology. An ophthalmologist is an M.D.
    Ophthalmology: The art and science of eye medicine.
    Ophthalmopathy: Eye disease.
    Optic: Having to do with vision.
    Optic neuroma: A benign tumor of the optic nerve.
    Optic nerve: The nerve that carries Messages from the retina to the brain.
    Optometrist: Professional trained to provide primary eye and vision care and improve vision with glasses, contact lenses, etc. An optometrist is an O.D. (Doctor of Optometry), not an M.D.
    Oral: Having to do with the mouth.
    Oral cancer: Cancer within the mouth. Please see MedicineNet site on RAL CANCER for more information.
    Oral surgeon: A dentist with special training in surgery of the mouth and jaw.
    Orbit: In medicine, the bony cavity in which the eyeball sits.
    Orbital ridge: The bony ridge beneath the eyebrow.
    Orchitis: Inflammation of the testis (male sex organ). There are many causes of inflammation of the testis including infections (such as mumps), diseases (such as polyarteritis nodosa), or injury. Also called orchiditis.
    Orchiectomy: The surgical removal of the testicles.
    Orifice: An opening. The mouth for example is an orifice.
    Oromandibular dystonia: Oro- refers to the mouth and mandibular refers to the lower jaw. Oromandibular dystonia affects the muscles of the jaw, lips, and tongue. The jaw may be pulled either open or shut, and speech and swallowing can be difficult.
    Oropharynx: The area of the throat at the back of the mouth.
    Ortho-: Prefix meaning straight or erect.
    Orthodontic treatment (dental braces): Please see MedicineNet site on ORTHODONTIC TREATMENT for information on this subject.
    Orthopedics: Literally, the practice of child straightening, orthopedics is the branch of surgery broadly concerned with the skeletal system (bones).
    Orthopedist: An orthopedic surgeon.
    Orthopod: Slang for orthopedist.
    Orthopnea: The plight of a person who can only breath easily when sitting straight or standing erect.
    Orthostatic hypotension: A temporary low blood pressure (hypotension) due usually to suddenly standing up (orthostatic). Symptoms such as dizziness, feeling about to black out, and tunnel vision can be due to insufficient blood flow to the brain. The symptoms are typically worse when standing and improve with lying down. Orthostatic hypotension may be experienced by healthy people who rise quickly from a chair, especially after a meal, and have a few seconds of disorientation.
    Osseous: Having to do with the bone.
    Osteo-: Prefix meaning bone.
    Osteoarthritis: Type of arthritis caused by inflammation, breakdown and eventual loss of the cartilage of the joints. For more information on this common type of arthritis, please see the MedicineNet site on OSTEOARTHRITIS.
    Osteochondroma: An abnormal solitary benign growth of bone and cartilage typically at the end of a long bone. Osteochondromas are usually discovered in persons 15 to 25 years of age. They are typically detected when injured or they become large enough to be noted.
    Osteodystrophy (renal osteodystrophy): A combination of bone disorders usually caused by chronic kidney failure (renal disease). Please see the MedicineNet site on OSTEODYTROPHY for more information.
    Osteogenesis: The production of bone.
    Osteogenesis imperfecta: Brittle bone disease.
    Osteomalacia: Softening of the bone.
    Osteomyelitis: Inflammation of the bone due to infection, for example by the bacteria salmonella.
    Osteonecrosis (aseptic necrosis or avascular necrosis): Condition resulting from poor blood supply to an area of bone causing bone death. For more information on this condition, please see the MedicineNet site on OSTEONECROSIS.
    Osteopath: An osteopathic physician who is a Doctor of Osteopathy (D.O.).
    Osteopathy: A system of therapy founded in the 19th century based on the concept that the body can formulate its own remedies against diseases when the body is in a normal structural relationship, has a normal environment and enjoys good nutrition.
    Osteopetrosis: Stony bones; thickening of the bones, also called marble bones.
    Osteoporosis: Thinning of the bones with reduction in bone mass due to depletion of calcium and bone protein, predisposing to fractures. For more information, please see the MedicineNet site on OSTEOPOROSIS.
    Osteosarcoma: A cancer of the bone that is most common in children. Also called osteogenic sarcoma.
    Osteotomy: Taking out part or all of a bone.
    Ostomy: An operation to create an opening from an area inside the body to the outside. See glossary entry for colostomy.
    Otitis: Inflammation of the ear.
    Otitis externa: Inflammation of the external ear canal that leads inward to the ear drum (tympanic membrane).
    Otitis interna: Inflammation of the inner ear.
    Otitis media: Inflammation of the middle ear, often due to an infection. Very common in children.
    Oto-: Prefix meaning ear.
    Otolaryngologist: A doctor who specializes in treating diseases of the ear, nose, and throat.
    Otoscope: Instrument for looking in the ear. Today, otoscopic or ophthalmoscopic heads can usually be attached to the base (which supplies the electrical power) to look at the ears or eyes.
    Ounce: A measure of weight equal to 1/16th of a pound or, metrically, 28.35 grams. The abbreviation for ounce is oz. (An ounce of prevention is reputedly worth a pound of cure.)
    Outpatient: A patient who is not an inpatient (not hospitalized). Outpatient care is called ambulatory care.
    Ova: Two or more "ovums". (Ova is the plural of ovum).
    Ovarian cancer: Cancer of the ovary. Most often due to ovarian carcinoma. For more information on this important women's health problem, please see the MedicineNet site on OVARIAN CANCER.
    Ovaries: The pair of female reproductive organs that produce eggs (ova) and hormones. They are located in the lower abdomen, one on each side of the uterus.
    Ovary: An ovary or "egg sac" is one of a pair of reproductive glands in women. The ovaries produce the ovum or female egg which is transferred through the fallopian tube for fertiliztion by the sperm. The ovary also produces both the hormones estrogen and progesterone.
    Overgrowth: Just what it sounds like: excessive growth.
    Overgrowth syndromes: Conditions with multiple abnormalities including excessive growth. Early overgrowth syndromes that affecting children include the fragile X and Beckwith-Wiedemannn syndromes. Overactivity of the pituitary gland with overproductiuon of growth hormone causes overgrowth before adolescence and a distinctive pattern of overgrowth called acromegaly.
    Overweight: Obesity. Please see MedicineNet site on OBESITY for information.
    Ovulation: The release of the ripe egg from the ovary.
    Ovum: An ovum is an egg that exists in the ovary of the female. This egg is called the female "gamete" or sex cell. It combines with the male gamete, called a sperm, to form a zygote. This formation process is called "fertilization." (see sperm, zygote).
    Oxyuris: A group of intestinal worms that includes pinworm.

    oz.: Abbreviation for ounce.
  • p arm of a chromosome: The short arm of a chromosome (from the French petit meaning small). All human chromosomes have 2 arms: the p and q arms.
    p in biochemistry: The abbreviation for protein. For example, p53 is a protein (53 kilodaltons in size).
    p in population genetics: The frequency of the more common of two different alternative (allelic) versions of a gene. (The frequency of less common allele is q).
    p53: A protein (53 kilodaltons in size) produced by a tumor-suppressor gene. Like other tumor-suppressor genes, the p53 gene normally controls cell growth. If p53 is physically lost or functionally inactived, this allows cells to grow without restraint.
    PA: A physician’s assistant (P.A.) or, in anatomy, PA stands for posteroanterior: from back-to-front. See: PA X-ray.
    PA X-ray: An X-ray picture in which the beams pass from back-to-front (posteroanterior). As opposed to an AP (anteroposterior) film in which the rays pass through the body from front-to-back.
    Paediatrics: Pediatrics in Great Britain.
    Paget's disease: A condition of unknown cause in which the bone formation is out of synchrony with normal bone remodeling.
    Pain: It may seem ludicrous to define a sensation that most everyone has experienced (except, for example, people born with complete insensitivity to pain). One standard reference work defines pain as a "more or less localized sensation of discomfort, distress, or agony, resulting from the stimulation of specialized nerve endings."
    Pain, ankle: The ankle is a "hinged" joint. The severity of ankle sprains ranges from mild (which can resolve within 24 hours) to severe (which can require surgical repair). Tendinitis of the ankle can be caused by trauma or inflammatory arthritis.
    Pain, back: Symptoms in the low back can relate to the bony lumbar spine, discs between the vertebrae, ligaments around the spine and discs, spinal cord and nerves, muscles of the low back, internal organs of the pelvis and abdomen, and the skin covering the lumbar area.
    Pain, chest: Chest pain has many cause. One celebrated cause is angina which results from inadequate oxygen supply to the heart muscle due to coronary artery disease or spasm of the coronary arteries. Treatment of angina includes rest, medication, angioplasty, and/or coronary artery bypass surgery.
    Pain, elbow: Tendinitis can affect the inner or outer elbow. Treatment includes ice, rest, and medication for inflammation. Bacteria can infect the skin of a scraped (abraded) elbow and cause pain.
    Pain, knee: Causes of knee pain include injury, degeneration, arthritis, infrequently infection and rarely bone tumors.
    Pains, growing: Mysterious pains in growing children, usually in the legs. These pains are similar to what the weekend gardener suffers from on Monday—an overuse type of problem. If in playing, children exceed their regular threshold, they will be sore, just like an adult. Growing pains are typically somewhat diffuse (vs. focal) and are not associated with physical changes of the area (such as swelling, redness, etc.). The pains are usually relieved by Messages, Tylenol (acetaminophen), or rest. If the pains persist past a week or there are physical changes, the child should be seen by a physician.
    Palate: The roof of the mouth. The front portion is bony (hard palate), and the back portion is muscular (soft palate).
    Palate, cleft: An opening in the roof of the mouth, due to a failure of the palatal shelves to come fully together from either side of the mouth and fuse during embryonic development.
    Palate, hard: The bony part of the roof of the mouth. The hard palate is just in front of the soft palate.
    Palate, soft: The muscular part of the roof of the mouth. The soft palate is directly behind the hard palate. It lacks bone and so is soft.
    Palindrome in genetics: A palindrome is a word that reads the same in both directions as, for example, the names Eve or Anna. In genetics, a palindrome is a DNA or RNA sequence that reads the same in both directions. The sites of many restriction enzymes that cut (restrict) DNA are palindromes. Palindromic rheumatism is a form of joint inflammation whereby the joints involved appears to change periodically from one region of the body to another and back again.
    Palliate: To treat a disease partially and insofar as possible but not cure it completely.
    Pallister-Killian syndrome: A condition with multiple malformations at birth and mental retardation due to isochromosome 12p mosaicism (an abnormal chromosome #12 in some cells).
    Palmar surface: The palm or grasping side of the hand.
    Palpate: To touch or feel. The liver's edge may be palpated.
    Palpebra: Medical term for eyelid. The plural is palpebrae.
    Palpebral fissure: The opening for the eyes between the eyelids.
    Palpitations: Unpleasant sensations of irregular and/or forceful beating of the heart. In some patients with palpitations, no heart disease or abnormal heart rhythms can be found. In others, palpitations result from abnormal heart rhythms (arrhythmias). Arrhythmias refer to heartbeats that are too slow, too rapid, irregular, or too early.
    Palsy: Paralysis, generally partial, whereby a local body area is incapable of voluntary movement (motor function). For example, Bell's palsy is localized paralysis of the muscles on one side of the face.
    Pancreas: An organ of the digestive system located behind the stomach.
    Pancreatic: Having to do with the pancreas.
    Pancreatitis: Inflammation of the pancreas. Of many diverse causes, the most common are alcohol and gallstones.
    Pancreatic cancer: Cancer of the pancreas. When pancreatic cancer spreads, it usually travels through the lymphatic system. Surgeons often remove lymph nodes near the pancreas to learn whether they contain cancer cells.
    Pancreatic insufficiency: Not enough of the digestive enzymes normally secreted by the pancreas into the intestine. Pancreatic insufficiency is a hallmark of cystic fibrosis.
    Pancreatic juices: Fluids made by the pancreas that contain digestive enzymes.
    Pancytopenia: A shortage of all types of blood cells.
    Pancytopenia, Fanconi: A genetic (inherited) disease with progressive decline in blood cells and a tendency to leukemia. Also known as Fanconi anemia.
    Pandiculation: One of the more wondrous medical words, pandiculation is the act of stretching and yawning. (If in a public place, you might consider demonstating the versatility of your vocabulary by saying, "Sorry, but I feel the need to pandiculate.")
    Panic disorder: Symptoms of panic attack usually begin abruptly and include rapid heartbeat, chest sensations, shortness of breath, dizziness, tingling, and anxiousness. Treatments include several medications and psychotherapy.
    PAP test: Microscopic examination of cells collected from the cervix. It is used to detect changes that may be cancer or may lead to cancer, and it can show noncancerous conditions, such as infection or inflammation. Also called Pap smear.
    Papillary muscle: Small muscles within the heart which anchor the heart valves.
    Papillary tumor: A tumor shaped like a small mushroom with its stem attached to the inner lining of the bladder.
    Papilledema: Swelling around the optic nerve, usually due to pressure on the nerve by a tumor.
    Papilloma: A benign tumor that projects above the surface of the tissue from which it arises. Papillomas have clearcut borders and are usually small and fairly round.
    Papilloma virus, human (HPV): A family of over 60 viruses responsible forcausing warts. The majority of the viruses produce warts on the hands, fingers, and even the face. Most of these viruses are innocuous, causing nothing more than cosmetic concerns. Several types of HPV are confined primarily to the moist skin of the genitals, producing genital warts and elevating the risk for cancer of the cervix. These viruses that cause wartlike growths on the genitals and contrribute to cancer of the cervix are sexually transmitted.
    Papillomatosis: A disorder with numerous papillomas.
    Papillomatosis, laryngeal: Warty growths on the vocal cords. Most common in young children. Recurrences are, unfortunately, frequent. Remission may occur after several years. Papillomatosis of the larynx can be due to the baby contracting human papilloma virus (HPV) during birth through the vaginal canal from a mother with genital warts (which are due to HPV). Each year, about 300 infants are born with the virus on their vocal cords because of maternal transmission.
    Papule: A small solid rounded elevation from the skin.
    Paracentric inversion: A basic type of chromosome rearrangement. A segment that does not include the centromere (and so is paracentric) has been snipped out of a chromosome, turned through 180 degrees (inverted), and inserted right back into its original location in chromosome.
    Paralysis: Loss of voluntary movement (motor function); may be partial (palsy) or total, such as in botulism.
    Paraneoplastic syndrome: A group of symptoms caused by substances produced by certain cancer cells.
    Paraphilia: Paraphilias are a variety of complex psychiatric disorders which are manifest as deviant sexual behavior. For example, in men the most common forms are pedophilia (sexual behavior toward children) and exhibitionism (exposing one’s body in public setting). Men with paraphilia are usually treated with psychotherapy, antidepression medications, and medications that alter hormones, particularly testosterone (male sex hormone).
    Paraquat lung: Paraquat, a weed killer, selectively accumulates in the lungs and is highly toxic. Once X-ray changes from paraquat are evident in the lungs, death is virtually certain.
    Parasite: A plant or animal organism that lives in or on and takes its nourishment from another. Parasite diseases include infections due to protozoa, helminths, or arthropods. For examples: Malaria is caused by plasmodium, a protozoa (a single-cell organism that can only divide within a host organism). Schistosomiasis, another set of very important parasitic diseases, is caused by a helminth (a worm). The arthropods include insects and arachnids (spiders, etc.), a number of which can act as vectors (carriers) of parasitic diseases.
    Parasympathetic nervous system: A part of nervous system that serves to slow the heart rate, increase the intestinal and gland activity, and relax the sphincter muscles. The parasympathetic nervous system, together with the sympathetic nervous system (that accelerates the heart rate, constricts blood vessels, and raises blood pressure), constitutes the autonomic nervous system.
    Parathormone: Hormone made by the parathyroid gland (behind the thyroid gland in the neck). Parathormone (pronounced para-thor-mone) is critical to calcium and phosphorus balance. Deficiency of parathormone results in abnormally low calcium in the blood (hypocalcemia). Alternative name is parathyrin.
    Parathyrin: See Parathormone.
    Parathyroid: Gland that regulates calcium, located behind the thyroid gland in the neck. The parathyroid secretes a hormone called parathormone (or parathyrin) that is critical to calcium and phosphorus metabolism. Although the number of parathyroid glands can vary, most people have four, one above the other on each side. They are plastered against the back of the thyroid and therefore at risk for being accidentally removed during thyroidectomy.
    Parathyroid hormone: See Parathormone.
    Parathyroids, hypoplasia of the thymusand: Also known as the DiGeorge syndrome (DGS), this disorder is characterized by (1) low blood calcium levels (hypocalcemia) due to underdevelopment (hypoplasia) of the parathyroid glands which control calcium; (2) underdevelopment (hypoplasia) of the thymus, an organ behind the breastbone in which lymphocytes mature and multiply; and (3) defects of the heart involving the outflow tracts from the heart. Most cases of DGS are due to a microdeletion in chromosome band 22q11.2. A small number of cases have defects in other chromosomes, notably 10p13. Named after the American pediatric endocrinologist Angelo DiGeorge. Another name for DGS is the third and fourth pharyngeal pouch syndrome.
    Parenteral: Not enteric (by the intestine). Something given by injection is parenteral.
    Parenteral nutrition: Intravenous feeding. Same as parenteral alimentation.
    Paresis: Incomplete paralysis.
    Paresis, general: A part of late ("tertiary") syphilis a decade or more after the initial infection, due to chronic inflammation of the covering and substance of the brain (meningoencephalitis) which results in progressive dementia and generalized paralysis.
    Paresthesia: An abnormal sensation of the body, such as numbness, tingling, or burning.
    Parietal bone: The side bone of the skull.
    Parietal lobe: Part of the brain and specifically a section of thecerebral hemisphere.
    Parkinson's disease: Parkinson's disease is an abnormal condition of the nervous system caused by degeneration of an area of the brain called the basal ganglia. The disease results in rigidity of the muscles, slow body movement and tremor. Parkinson's disease is also called "paralysis agitans" and "shaking palsy."
    Paroxysmal atrial tachycardia (PAT): Bouts of rapid, regular heart beating originating in the atrium (upper chamber of the heart). Due to abnormalities in the AV node "relay station" that lead to rapid firing of electrical impulses from the atrium which bypass the AV node under certain conditions. These conditions include alcohol excess, stress, caffeine, overactive thyroid or excessive thyroid hormone intake, and certain drugs. PAT is an example of an arrhythmia where the abnormality is in the electrical system of the heart, while the heart muscle and valves may be normal.
    Parotid gland: The largest of the three major salivary glands, it is located in front and below the ear and behind the jaw bone. The other two glands are the submandibular (submaxillary) and sublingual.
    Parotids: Salivary glands situated in front of the ears.
    Parotitis: Inflammation of the parotid glands. A classic feature of mumps.
    Parrot fever (psittacosis): An infectious disease due to a bacteria (Chlamydia psittaci) contracted from psittacine birds, especially caged birds like parrots but also in turkey processing plants. The name psittacosis comes from the Greek "psittakos" meaning parrot.
    Parry’s disease: Toxic multinodular goiter. Named for the English physician Caleb Hillier Parry (1755-1822). also called Plummer’s disease.
    Parthenogenesis: Development of a germ cell without fertilization. This is what happens in the formation of some benign ovarian tumors called dermoids (ovarian teratomas). The term "parthenogenesis" comes from the Greek "parthenos" (virgin) + "genesis" (generation). The Greek goddess Artemis (called Parthenos, the virgin) was associated with nymphs who became pregnant and were transformed into beasts.
    Partial hysterectomy: In a partial hysterectomy, the uterus is surgically removed but the cervix is left in place. Also called a subtotal hysterectomy.
    Parturition: Childbirth.
    PAT: Paroxysmal atrial tachycardia.
    Patau syndrome: This is trisomy 13syndrome. There are three rather than the normal two chromosomes #13. Children with this syndrome have multiple malformations and mental retardation due to the extra chromosome #13. The malformations commonly include scalp defects, hemangiomas (blood vessel malformations) of the face and nape of the neck, cleft lip and palate, malformations of the heart and abdominal organs, and flexed fingers with extra digits. The mental retardation is profound. The IQ is untestably low. The majority of trisomy 13 babies die soon after birth or in infancy. Named after the late geneticist Klaus Patau (from the University of Wisconsin) who described the extra chromosome in 1960.
    Patella: The kneecap.
    Patent (noun): A device giving exclusive control and possession. Before the commercialization of biomedical inventions, the word "patent" in this sense had no place in a medical dictionary. Now the patent is the foundation of the biotechnology industry.
    Patent (adjective): Pronounced pa’tent with the accent on the first syllable, patent means open, unobstructed, affording free passage. Thus, the bowel can be patent (as opposed to obstructed).
    Patent ductus arteriosus (PDA): Before birth, the blood headed from the heart via the pulmonary artery toward the lungs is shunted into the greatest of arteries (the aorta). The shunt is a short vessel called the ductus arteriosus. When the shunt is open, it is said to be patent (pronounced pa’tent). The patent ductus arteriosus (PDA) usually closes at or shortly after birth permitting blood from that moment on to course freely to the lungs. If the ductus remains open (patent), flow reverses and blood from the aorta is shunted into the pulmonary artery and recirculated through the lungs. The PDA may close later spontaneously (on its own) or need to be ligated (tied off) surgically.
    Pathologist: A doctor who identifies diseases by studying cells and tissues under a microscope.
    Pavlov conditioning: See: Pavlovian conditioning.
    Pavlov conditioning: The Russian physiologist Ivan Petrovich Pavlov (1848-1936) conditioned dogs to respond in what proved to be a predictable manner, for example, by first ringing a bell before feeding them and then simply ringing the bell upon which stimulus they would begin to salivate as if they were about to eat.
    Pavlov pouch: At different points along the dogs’ digestive tracts, the Russian physiologist Ivan Petrovich Pavlov (1848-1936) surgically created pockets ("Pavlov pouches") from which he could obtain secretions, the aim being to study the physiology of the digestive tract. He did so from the salivary glands down to the stomach, liver and pancreas with considerable success and in 1904 (the 4th year it was awarded) he received the Nobel Prize for "his work on the physiology of digestion, through which knowledge on vital aspects of the subject has been transformed and enlarged."
    Pavlov stomach: A Pavlov pouch fashionned surgically from part of the stomach (which is isolated from the rest of the stomach). The pouch opens through a fistula (canal) on to the abdominal wall and permits sampling of the gastric contents. See Pavlov pouch.
    PC: Although PC is usually taken to mean personal computer, in the biomedical arena PC also stands for protein C, phosphocreatinine, et al.
    PCO: Polycystic ovarian disease (or the Stein-Leventhal syndrome).
    PCP: Pneumocystis carinii pneumonia. A parasitic infection of the lungs that is particularly common and life-threatening in immunosuppressed persons. Prophylaxis is available to prevent PCP.
    PCR: Stands for Polymerase Chain Reaction, a key technique in molecular genetics that permits the analysis of any short sequence of RNA or DNA without having to clone it.
    PDA: Patent ductus arteriosus.
    PDR: Physicians’ Desk Reference (please see entry to Physicians’ Desk Reference). PDR less frequently stands for "postdelivery room".
    Pectus carinatum: Pigeon-breasted.
    Pectus excavatum: Caved-in or funnel chest.
    Pediatric: Pertaining to children.
    Pediatric arthritis: Arthritis is not just a problem for the retired. It can and does affect children in the form of pediatric arthritis. Also called juvenile arthritis.
    Pediatrics: "Pediatrics is concerned with the health of infants, children and adolescents, their growth and development, and their opportunity to achieve full potential as adults." (R.E.. Behrman in Nelson's Textbook of Pediatrics)
    Pediculosis: Infested with lice.
    Pedigree: In medicine, a pedigree is a family health history diagrammed with a set of international symbols to indicate the individuals in the family, their relationships to one another, those with a disease, etc.
    Pedodontics: Chilldren's dentistry.
    Pedophilia: Adult sexual activity with children. Considered a form of child abuse. Pedophilia literally means love of children.
    Pedigree: In medicine, a pedigree is a family health history diagrammed with a set of international symbols to indicate the individuals in the family, their relationships to one another, those with a disease, etc.
    Pellagra: From the Italian pelle, skin and agra. rough. Dermatitis is a feature of pellagra, a syndrome due to deficiency of niacin, one of the B-complex vitamins.
    Pelvic: Having to do with the pelvis, the lower part of the abdomen, located between the hip bones.
    Pelvic inflammatory disease (PID): Despite its seeming lack of gender, this term is applied to women only. PID refers exclusively to ascending infection of the female genital tract above the cervix.
    Pelvis: The lower part of the abdomen located between the hip bones. Organs in the female pelvis include the uterus, vagina, ovaries, fallopian tubes, bladder, and rectum. Pendred syndrome: Hereditary association of congenital deafness and goiter (enlargement of the thyroid gland in the front of the neck) due to a defect in the making of thyroid hormone.
    Penetrance: The likelihood a given gene will result in disease. For example, if half (50%) of the people with the neurofibromatosis (NF) gene have the disease NF, the penetrance of the NF gene is 0.5.
    Penicillin: Historically, the most famous of antibiotics. Named for the Penicillium fungal mold from which it came. Chicken soup, long known as Jewish penicillin, may in reality have some therapeutic merit.
    Penis: Defined by the Oxford English Dictionary as the "intromittent" organ of the male. ("Intromittent " is defined as "That intromits or introduces; having the function of intromission"). In Latin, "penis" originally meant "a tail."
    Penis, erection of the: When the penis fills with blood and is rigid. The penis contains two chambers, called the corpora cavernosa, which run the length of the organ, are filled with spongy tissue, and surrounded by a membrane, called the tunica albuginea. The spongy tissue contains smooth muscles, fibrous tissues, spaces, veins, and arteries. The urethra, which is the channel for urine and ejaculate, runs along the underside of the corpora cavernosa. Erection begins with sensory and mental stimulation. Impulses from the brain and local nerves cause the muscles of the corpora cavernosa to relax, allowing blood to flow in and fill the open spaces. The blood creates pressure in the corpora cavernosa, making the penis expand. The tunica albuginea helps to trap the blood in the corpora cavernosa, thereby sustaining erection. Erection is reversed when muscles in the penis contract, stopping the inflow of blood and opening outflow channels.
    Peptic ulcer: A hole in the lining of the stomach, duodenum, or esophagus. A peptic ulcer of the stomach is called a gastric ulcer, an ulcer of the duodenum is a duodenal ulcer, and a peptic ulcer of the esophagus is an esophageal ulcer. A peptic ulcer occurs when the lining of these organs is corroded by the acidic digestive juices which are secreted by the stomach cells.
    Peptic ulcer disease is common, affecting millions of Americans yearly. The medical cost of treating peptic ulcer and its complications runs in the billions of dollars annually in the U.S.. Recent medical advances have increased our understanding of ulcer formation. Improved and expanded treatment options are now available.
    Percentile: The percentage of individuals in a group who have achieved a certain quantity (such as height, weight, and head circumference) or developmental milestone (such as "walking well" the 50th percentile for which is12 months of age).
    Pericardial effusion: Too much fluid within the fibrous sac (the pericardium) that surrounds the heart.
    Pericarditis: Inflammation of the lining around the heart (the pericardium) causing chest pain and accumulation of fluid around the heart (pericardial effusion).
    Pericardium: A sac of fibrous tissue which surrounds the heart. The inner surface is lined by mesothelial cells and the sac normally contains a small amount of fluid which acts as a lubricant to allow normal heart movement within the chest.
    Pericentric inversion: A basic type of chromosome rearrangement. A segment that includes the centromere (and so is pericentric) has been snipped out of a chromosome, turned through 180 degrees (inverted), and inserted back into its original location in chromosome.
    Perineum: The area between the anus and the scrotum in the male and between the anus and the vulva (the labial opening to the vagina) in the female. An episiotomy is a surgical procedure to widen the outlet of the birth canal to facilitate delivery of the baby and avoid a jagged rip of the perineum.
    Periodontitis: Gum disease, gingivitis.
    Peripheral neuropathy: A problem with the functioning of the nerves outside the spinal cord. Symptoms may include numbness, weakness, burning pain (especially at night), and loss of reflexes.
    Peristalsis: The rippling motion of muscles in the digestive tract. In the stomach, this motion mixes food with gastric juices, turning it into a thin liquid.
    Peritoneal: Having to do with the peritoneum.
    Peritoneal dialysis: Technique that uses the patient’s own body tissues inside of the belly (abdominal cavity) to act as a filter. The intestines lie in the abdominal cavity, the space between the abdominal wall and the spine. A plastic tube called a "dialysis catheter" is placed through the abdominal wall into the abdominal cavity. A special fluid is then flushed into the abdominal cavity and washes around the intestines. The intestinal walls act as a filter between this fluid and the blood stream. By using different types of solutions, waste products and excess water can be removed from the body through this process.
    Peritoneum: The membrane that lines the abdominal cavity and covers most of the abdominal organs. (From the Greek peri- meaning around + tonos meaning a stretching = a stretching around).
    Peritonitis: Inflammation of the peritoneum (The peritoneum is the tissue layer of cells lining the inner wall of the abdomen and pelvis). Peritonitis can result from infection (such as bacteria or parasites), injury and bleeding, or diseases (such as systemic lupus erythematosus).
    Perfusion: A chemotherapy technique that may be used when melanoma occurs on an arm or leg. The flow of blood to and from the limb is stopped for a while with a tourniquet, and anticancer drugs are put directly into the blood of the limb. This allows the patient to receive a high dose of drugs in the area where the melanoma occurred.
    Perineal surgery: An operation to remove the prostate gland through an incision made between the scrotum and the anus.
    Peripheral blood stem cell transplantation: A procedure that is similar to bone marrow transplantation. Doctors remove healthy immature cells (stem cells) from a patient's blood and store them before the patient receives high-dose chemotherapy and possibly radiation therapy to destroy the leukemia cells. The stem cells are then returned to the patient, where they can produce new blood cells to replace cells destroyed by the treatment.
    Pernicious anemia: A blood disorder caused by a lack of vitamin B12. Patients who have this disorder do not produce the substance in the stomach that allows the body to absorb vitamin B12.
    Pertussis: This is whooping cough's medical name, It is the "P" in DPT vaccine. Immunity from DPT wears off, so many teen-agers and adults get pertussis, first as coughing spasms and then a stubborn dry cough lasting up to 6-8 weeks. Due to a bacteria (Bordetella pertussis). Therapy is supportive and many young infants need hospitalization if the coughing becomes severe. Immunization with DPT (diphtheria-pertussis-tetanus) vaccine provides protection. With pertussis, an ounce of prevention is worth a pound of cure (or, if you are metrically inclined, a gram of prevention is worth a kilo of cure). Have your child immunized!
    Pes: Latin for foot.
    Pes cavus: Literally a hollow foot, pes cavus is a foot with too high an arch.
    Pes planum: Flat feet.
    Petechiae: Tiny red spots in the skin which do not blanch when pressed upon. They result from red blood leaking from capillaries. They are not infrequently seen in the legs of patients taking aspirin because its mild blood-thinning effect.
    Petit mal: A form of epilepsy with very brief, unannounced lapses in consciousness. Petit mal (little illness in French) seizures are also known as absence seizures.
    Phage: Short for bacteriophage, a virus that naturally lives within a bacterial cell. Much used in molecular genetics.
    Phagocyte: A cell that can engulf particles such as bacteria and other microorganisms, foreign matter, etc. The principal phagocytes include the neutrophils and monocytes, both types of white blood cells.
    Phalanges: The name given to the bones of the fingers by Aristotle in the 4th century B.C. (and since extended to the bones of the toes) because they were arrayed like Greek soldiers for battle. The singular of phalanges is phalanx.
    Pharmacogenetics: The convergence of pharmacology and genetics dealing with genetically determined responses to drugs. For example, after the administration of a muscle relaxant commonly used in surgery, a patient may remains apneic incapable of breathing on their own for hours due to a genetically determined defect in metabolizing (processing) the muscle relaxant.
    Pharmacology: The study of drugs, their sources, their nature, and their properties.
    Pharmacopeia: An official authoritative listing of drugs. Aspirin has, for example, long been in the pharmacopeia.
    Pharyngeal: Having to do with the throat (pharynx).
    Pharyngitis: Inflammation of the pharynx (hollow tube in the back of the throat about 5 inches long that starts behind the nose and ends at the top of the trachea). Pharyngitis is a common cause for a sore throat.
    Pharynx: The hollow tube about 5 inches long that starts behind the nose and ends at the top of the trachea (windpipe) and esophagus (the tube that goes to the stomach).
    Phase, resting: More appropriately called interphase. The interval in the cell cycle between two cell divisions when the individual chromosomes cannot be distinguished, interphase was once thought to be the resting phase but it is far from a time of rest for the cell. It is the time when DNA is replicated in the cell nucleus.
    Ph.D.: Doctor of Philosophy. (From the New Latin, philosophiae doctor). PhDs are involved in clinical care (as in clinical psychology), biomedical research (as in the Genome Project), health administration and other areas in medicine.
    Phalanx: A general term for any one of the bones in the fingers or toes. There are generally three phalanges (distal, middle, proximal) for each digit, except the thumbs and large
    Phenocopy: A defect due to an environmental agent that imitates that produced by a specific gene.
    Phenotype: The appearance resulting from the interaction of the genetic makeup of a person with the environment. If a child has the gene for osteogenesis imperfecta (brittle bone disease), minimal trauma can cause fractures. Brittle bones are a principal part of the phenotype of osteogenesis imperfecta.
    Phenylketonuria (PKU): Inherited inability to process the amino acid phenylalanine. Newborns are screened for PKU. Treatment is a diet low in phenylalanine. Failure of treatment results in mental retardation.
    Philadelphia chromosome (Ph): The hallmark of chronic myeloid leukemia (CML). The Ph chromosome is an abbreviated chromosome #22 that was shortchanged in an exchange with chromosome #9. This exchange (a translocation) occurs in a bone marrow cell and causes CML.
    Philtrum: The area from below the nose to the upper lip. Normally the philtrum is grooved. In fetal alcohol syndrome, the philtrum is flat.
    Phimosis: The foreskin is too tight.
    Phlebo-: Means vein.
    Phlebitis: Inflammation of a vein. With phlebitis, there is infiltration of the walls of the vein and, usually, the formation of a clot (thrombus) in the vein (thrombophlebitis). Phlebitis in a leg, for example, will cause the leg to swell with edema fluid and feel stiff and painful.
    Phlebotomy: Obtaining blood from a vein. This may be for diagnostic tests or treatment (for example, to relieve the iron overload in hemochromatosis).
    Phlebotomist: A person who draws blood.
    Phocomelia: A congenital malformation (birth defect) in which the hands and feet are attached to abbreviated arms and legs. The word phocomelia combines phoco- (seal) and melia (limb) to designate a limb like a seal's flipper, one consequence of exposure of the developing fetus to thalidomide.
    Phobia: Fear.
    Phosphate: A form of phosphoric acid. Calcium phosphate makes bones and teeth hard.
    Phosphorus: An essential element in the diet and a major component of bone.
    Photodynamic therapy: Treatment that destroys cancer cells with lasers and drugs that become active when exposed to light.
    Photophobia: Painful oversensitivity to light.
    Photosensitivity: The skin is oversensitive to light.
    Phototherapy: Treatment with light. For example, a newborn with jaundice may be "put under the lights."
    Physical map: A map of the locations of identifiable landmarks on chromosomes. Physical distance is measured in base pairs. The physical map differs from the genetic map which is based purely on genetic linkage data. In the human genome, the lowest-resolution physical map is the banding patterns of the 24 different chromosomes. The highest-resolution physical map will be the complete nucleotide sequence of all chromosomes.
    Physician: Only in English is a physician engaged in medicine. In French, for example, a physicien is a physicist.
    Physician assistant: A healthcare professional (typically an R.N.) that is licensed to provide patient education, evaluation, a healthcare services. A physician assistant works along with the doctor to provide medical care to a group of patients. Also referred to as a PA.
    Physicians’ Desk Reference (PRD): This thick volume—the 1998 PDR runs 3,223 pages in length—is a guide to all the prescription drugs available in the United States. Although not exactly redcommended fare for bedtime reading, the PDR is a key reference to the American pharmacopeia. It is available in many bookstores in the U.S.
    Physiatrist: A physician specializing in physical medicine and rehabilitation. Physiatrists specialize in restoring optimal function to people with injuries to the muscles, bones, tissues, and nervous system (such as stroke victims).
    Phytanic acid storage disease (Refsum’s disease): A genetic disorder of the fatty acid phytanic acid which accumulates and causes a number of progressive problems including polyneuritis (inflammation of numerous nerves), diminishing vision (due to retinitis pigmentosa), and wobbliness (ataxia) caused by damage to the cerebellar portion of the brain (cerebellar ataxia).
    Pia mater: One of the meninges, the pia mater (the term means tender covering) is the delicate innermost membrane enveloping the brain and spinal cord. It is known informally as the pia.
    Pianist’s cramp: A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs when playing the piano (or another keyboard instrument such as the harpsichord). Similar focal dystonias have also been called writer’s cramp, typist’s cramp, musician’s cramp, and golfer’s cramp.
    Pica: A craving for something not normally regarded as nutritive. For example, dirt. Pica is a classic clue to iron deficiency in children. It also occurs in zinc deficiency. (Pica is Latin for magpie, a bird that gleans all sorts of things for its nest).
    Pick's disease: A form of dementia characterized by a slowly progressive deterioration of social skills and changes in personality leading to impairment of intellect, memory, and language.
    Pickwickian syndrome: The combination of obesity, somnolence, hypoventilation (underbreathing), and plethoric (red) face named after the "fat and red-faced boy in a state of somnolency" in Charles Dickens' novel The Pickwick Papers. (The same boy is thought by some to have had Prader-Willi syndrome).
    Pigeon breast: Prominence of the breast bone (sternum). Medically, pigeon breast is called pectus carinatum.
    PID: Pelvic Inflammatory Disease.

    Pigment: A substance that gives color to tissue. Pigments are responsible for the color of skin, eyes,

    and hair.
    Pill, the: Slang term for oral contraceptive pill (OCP).
    Pilonidal cyst: A special kind of abscess that occurs in the cleft between the buttocks. Forms frequently in adolescence after long trips that involve sitting.
    Pilonidal sinus: A dimple in the crease between the buttocks.
    Pimples: Oil (sebaceous) glands infected with bacteria, resulting in an inflamed area with pus formation. Pimples are due to overactivity of the oil glands located at the base of the hair follicles, especially on the face, back, chest, and shoulders.
    Pineal gland: A small gland located in the brain.
    Pineal region tumors: Type of brain tumors.
    Pineoblastoma: A type of brain tumor.
    Pineocytoma: A type of brain tumor.
    Pinguecula: A yellow spot on the white of the eye, usually toward the inside (nose side) of the eye, associated with aging. It looks fatty (in Latin the word pinguiculus means fattish), and is due to an accumulation of connective tissue.
    Pinguicula: Alternate spelling of pinguecula. Irrespective of spelling, the accent is on the second syllable which is pronounced gwek.
    Pinna: The ear or, to be more precise, the part of the ear that projects like a little wing from the head. In Latin, pinna means wing.
    Pit, ear: Tiny pit in front of the ear. Also preauricular pit. A minor anomaly of no great consequence in itself. More common in blacks than whites and in females than males. Can recur in families. The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Pituitary adenoma: A benign tumor of the pituitary, the master gland that controls other glands and influences numerous body functions including growth.
    Pituitary dwarfism: Short stature due to underpreformance of the pituitary gland (specifically of the anterior pituitary).
    Pituitary gigantism: Excessive growth due to overactivity of the pituitary gland (specifically of the anterior pituitary).
    Pituitary gland: The main endocrine gland; it produces hormones that control other glands and many body functions, especially growth.
    PKU: Short for phenylketonuria.
    Placebo: A "sugar pill" or any dummy medication. In a controlled clinical trial, one group may be given a medication and another group a placebo to learn if a difference are due to the medication or to the power of suggestion. Placebos are widely used in drug trials.
    Placenta: The organ joining the mother and fetus that permits the provision of oxygen and nutrients to the fetus and the release of carbon dioxide and waste products from the fetus to the mother. The word "placenta" means a flat cake. It is disk-shaped and at full term measures about 7 inches (18 cm) in diameter and a bit less than 2 inches (4 cm) thick. The upper surface of the placenta is smooth while the under surface is rough. The placenta and the fetal membranes are the afterbirth.
    Placenta, accessory: An extra placenta separate from the main placenta. Also called a succenturiate or supernumerary placenta. Placenta accreta: The abnormal adherence of the chorionic villi to the myometrium. The vascular processes of the chorion (a fetal membrane that enters into the formation of the placenta) grow directly in the myometrium (the muscular portion of the uterus). Normally there is tissue intervening between the chorionic villi and the myometrium. Here there is not. The word "accreta" comes from the Latin "accretio" from "ad" meaning "to" or "toward" + "crescere" meaning "to grow". Placenta accreta can progress to placenta percreta.
    Placenta percreta: The placenta invades the uterine wall. In placenta percreta, the chorionic villi (the vascular processes of the chorion, a fetal membrane that enters into the formation of the placenta) may invade the full thickness of the myometrium (the muscular portion of the uterus) causing an incomplete rupture of the uterus. Or the chorionic villi can go right on through the myometrium and serosa (the outside covering of the uterus) causing complete rupture of the uterus, a catastrophe.
    Placenta praevia: A placenta implanted near the outlet of the uterus so that at the time of delivery the placenta would precede (be previous to) the baby. Causes painless bleeding in the last third of pregancy. One reason for a C-section.
    Placenta, succenturiate: An extra placenta separate from the main placenta. In anatomy "succenturiate" means accessory to an organ. In this case, a succenturiate placenta is an accessory placenta.
    Placenta, supernumerary: A succenturiate or accessory placenta.
    Plaque: (1) Dental plaque is the soft accumulation of food debris and bacteria around teeth. These bacteria feed on left over food in the mouth to excrete toxins that irritate the gums and dissolve the bone. Plaque can be removed by proper brushing and flossing at home. Once plaque is left around the teeth for a long time, it acquires minerals from the saliva and from foods which harden it into tartar. Tartar can become as hard as a rock and then can require a dentist or dental hygienist with special tools to remove it. Dental plaque and tartar cause inflammation of the bone surrounding the teeth referred to as "periodontia."
    (2) Plaque of an artery refers to hard formation on the artery walls formed by fat and cholesterol deposit over the years. These leads to hardening of the arteries called "atherosclerosis."
    Plantar: Having to do with the sole of the foot.
    Plantar fasciitis: Inflammation of the plantar fascia (fasciitis), the "bowstring-like" tissue stretching underneath the sole which attaches at the heel.
    Plasma: The liquid part of the blood. Plasma is devoid of cells and, unlike serum, has not clotted.
    Plasma cells: Special white blood cells that produce antibodies.
    Plasmacytoma: A tumor that is made up of cancerous plasma cells.
    Plasmapheresis: A procedure whereby plasma (which contains proteins, such as antibodies) is separated and removed from the blood and replaced with another solution, such as saline or albumin.
    Plasmid: A self-replicating (autonomous) circle of DNA distinct from the chromosomal genome of bacteria. A plasmid contains genes normally not essential for cell growth or survival. Some plasmids can integrate into the host genome, be artificially constructed in the laboratory, and serve as vectors (carriers) in cloning.
    Plasmodium: The parasite guilty in the case of malaria (paludism). Plasmodium is a type of protozoa, a single-celled organism able to divide only within a host cell.
    Plastic surgeon: A surgeon who specializes in reducing scarring or disfigurement that may occur as a result of accidents, birth defects, or treatment for diseases (such as melanoma).
    Platelets: Platelets are irregular disc-shaped elements of the blood which assist in blood clotting. Other major blood elements include protein, serum and red and white blood cells. Although platelets are classed as blood cells, they are not. They are fragments of a large cells called megakaryocytes (literally, large cells).
    Pleiotropic: Multiple effects from a single gene. For example, the Marfan gene is pleiotropic with widespread effects and can cause long fingers and toes (arachnodactyly), dislocation of the lens of the eye, and dissecting aneurysm of the aorta.
    Pleomorphic: Many-formed. A tumor may be pleomorphic. Pleomorphic is synonymous with protean (capable of assuming different shapes like the many-formed Greek god Proteus).
    Plethoric: Florid, red-faced.
    Pleura: The thin covering that protects and cushions the lungs. The pleura is made up of two layers of tissue that are separated by a small amount of fluid.
    Pleural effusion: Outpouring of fluid between the two layers of the pleural membranes that cover the lungs.
    Pleural space: Although reference is often made to the "pleural space" (one dictionary defines "pleural effusion" as "the presence of fluid in the pleural space"), there is normally only a small amount of fluid between the two layers of the pleura.
    Pleurisy: Pain as a result of inflammation of the pleural membrane that envelops the lungs. Pleurisy is typically noted as pain in the involved area of the chest with breathing.
    Pleuritis: Inflammation of the pleura (The thin covering that protects and cushions the lungs). The pleura is made up of two layers of tissue that are separated by a small amount of fluid. When the pleura becomes inflamed, it can produce more than the normal amount of fluid in this space. This is called a pleural effusion.
    Plumbism: Another name for lead poisoning.
    Plummer’s disease: Toxic multinodular goiter. Also called Parry’s disease.
    PMR (PolyMyalgia Rheumatica): A disorder of the muscles and joints of older persons characterized by pain and stiffness, affecting both sides of the body, and involving the shoulders, arms, neck, and buttock areas.
    PMS (PreMenstrual Syndrome): A combination of emotional, physical, psychological, and mood disturbances that occur after ovulation and normally end with the onset of the menstrual flow.
    Pneumatic larynx: A device that uses air to produce sound to help a laryngectomee talk.
    Pneumo-: Combining form pertaining to breathing, respiration, the lungs, pneumonia, or air. Pneumo- is derived from the Greek pneuma meaning wind, air, or breath. In French, pneu is a tire (so called because it contains air).
    Pneumococcal pneumonia immunization: This vaccine, which prevents one of the most common and severe forms of pneumonia, is usually given only once in a lifetime, usually after the age of 55, to someone with ongoing lung problems (such as chronic obstructive pulmonary disease (COPD) or asthma) or other chronic diseases (including those involving the heart and kidneys). This vaccination would rarely be given to children.
    Pneumococcus (Streptococcus pneumoniae): The #1 cause of bacterial pneumonia and otitis media (middle ear infection) and the #3 cause of bacterial meningitis.
    Pneumoconiosis: Deposition of particulate matter (such as asbestos and silicon) in the lungs.
    Pneumocystis carinii pneumonia (PCP): A parasitic infection of the lungs that is particularly common and life-threatening in immunosuppressed persons. Prophylaxis (preventative treatment) is available to prevent PCP.
    Pneumomediastinum: Free air in the mediastinum (space betweens the lungs) which may give rise to pneumothorax or pneumopericardium and compromise the lungs or heart.
    Pneumonectomy: An operation to remove an entire lung.
    Pneumonia: An infection that occurs when fluid and cells collect in the lungs.
    Pneumonia, aspiration: Inflammation of the lungs due to aspiration (the sucking in of food particles or fluids into the lungs).
    Pneumopericardium: Air between the heart and the pericardium, the membrane wrapped around the heart.
    Pneumothorax: Free air in the chest outside the lung. Pneumothorax can occur spontaneously ("out of the blue"), follow a fractured rib, occur in the wake of chest surgery, or be deliberately induced in order to collapse the lung.
    Podiatrist: A nonmedical specialist in caring for the foot.
    Poikiloderma atrophicans and cataract: The Rothmund-Thomson syndrome (RTS), a genetic disorder with numerous features affecting skin (premature aging, excess pigmentation, dilated blood vessels),eyes ( uvenile cataract), nose (saddle nose), teeth (maldeveloped), skeletal system (congenital bone defects) hair (abnormal), gonads (underdevelopment) limbs (soft tissue contractures), growth (short stature). blood (anemia) and a tendency to develop a type of bone cancer (osteogenic sarcoma). The RTS gene is on chromosome 8. The syndrome is recessive so to be affected with RTS a child has to have two RTS genes, one from each parent.
    Point mutation: A single nucleotide base change in the DNA, as for example in sickle cell disease.
    Poison ivy: Poison ivy is a form of "contact dermatitis" or inflammation of the skin resulting from chemicals produced from the poison ivy vine contacting the skin. The chemicals cause an immune reaction producing redness, itching and blistering of the skin.
    Poison oak: Poison oak is a form of "contact dermatitis" or inflammation of the skin resulting from chemicals produced from the poison oak plant contacting the skin. The chemicals cause an immune reaction producing redness, itching and blistering of the skin.
    Poisoning: Taking a substance which is injurious to health or can cause death. Poisoning is still a major hazard to children despite child-resistant (and sometimes adult-resistant) packaging and dose-limits per container. Please see MedicineNet's Poison Control Centers.
    Polio: Short for poliomyelitis.
    Polio immunization: The vaccines available for vaccination against polio are OPV (Oral Polio Vaccine) and IPV (Inactivated Polio Vaccine). OPV is still the preferred vaccine for most children. As its name suggests, it is given by mouth. IPV, or Inactivated Polio Vaccine is given as a shot in the arm or leg. Infants and children should be given four doses of OPV. The doses are given at 2 months, 4 months, 6-18 months and 4-6 years of age. Persons allergic to eggs or the drugs neomycin or streptomycin should receive OPV, not the injectable IPV. Conversely, IPV should be given If the vaccine recipient is on long-term steroid (cortisone) therapy, has cancer, or is on chemotherapy or if a household member has AIDS or there is an unimmunized adult in the house.
    Poliomyelitis: An acute and sometimes devastating viral disease. There is inflammation of the central nervous system, especially the anterior horn cells of the spinal cord and the brainstem (the portion of the brain between the cerebral hemispheres and spinal cord). Also called infantile paralysis.
    Pollen: Small, light, dry protein particles from plants (trees, grasses, and weeds) spread by the wind. Pollen particles are usually the male sex cells of the plant and are smaller than the tip of a pin or less than 40 microns in diameter. Even though pollen is a potent stimulator of allergy. It lodges in the nasal lining tissues (mucus membranes) and other parts of the respiratory tract where it does harm to the person of allergy.
    Pollex: The thumb.
    Poly: (1) A prefix meaning much or many; (2) An informal term for polymorhonuclear leukocyte (a type of white blood cell).
    Polyarteritis nodosa: An autoimmune disease (immune system attacking its own body) characterized by spontaneous inflammation of the arteries (arteritis) of the body. Because arteries are involved, the disease can affect any organ of the body, most commonly muscles, joints, intestines, nerves, kidneys, and skin.
    Polyarticular: Involving many joints. As opposed to monoarticular (affecting just one joint). From the Latin "articulus," meaning a joint.
    Polycystic kidney disease: Genetic (inherited) disorders characterized by the development of innumerable cysts in the kidneys filled with fluid that replace much of the mass of the kidneys and reduce kidney function leading to kidney failure.
    Polycystic ovarian disease: An hormonal problem that causes women to have a variety of symptoms including irregular or no periods, acne, obesity and excessive hair growth. Women with PCO are at a higher risk for uterine cancer (endometrial cancer), diabetes, high blood pressure, and heart disease. With proper treatment, risks can be minimized. PCO is also known as Stein-Leventhal syndrome.
    Polycythemia: The opposite of anemia. Too many red blood cells. Polycythemia formally exists when the hemoglobin, red blood cell (RBC) count, and total RBC volume are all above normal.
    Polycythemia vera (PV): Overproduction (proliferation) of red blood cells due to bone marrow disease (myeloproferative disorder). PV tends to evolve into acute leukemia or a condition with the marrow replaced by scar tissue (myelofibrosis)
    Polydactyly: More than the normal number of fingers or toes.
    Polydipsia: Excessive thirst all the time. Polydipsia occurs, for example, in untreated or poorly controlled diabetes mellitus.
    Polygenes: Many genes. Eye color is polygenically controlled.
    Polygenic diseases: Genetic disorders that are caused by the combined action of more than one gene. Examples of polygenic conditions include hypertension, coronary heart disease, diabetes, and peptic ulcers. Because such disorders depend on the simultaneous presence of several genes, they are not inherited as simply as single-gene diseases.
    Polyhydramnios: Too much amniotic fluid.
    Polymerase chain reaction (PCR): A key technique in molecular genetics that permits the analysis of any short sequence of RNA or DNA without having to clone it.
    Polymerase, DNA: Enzyme that catalyzes (speeds) the polymerization of DNA. DNA polymerase uses preexisting nucleic acid templates and assembles the DNA from deoxyribonucleotides.
    Polymerase, RNA: Enzyme that catalyzes (speeds) the polymerization of RNA. RNA polymerase uses preexisting nucleic acid templates and assembles the RNA from ribonucleotides.
    Polymorphism: The existence of two (or more) forms of a gene with each form being too common to be due merely to new mutation. Examples of polymorphic genes include sickle cell, thalassemia and G6PD, all of which are believed to have become common because they offer an advantage against malaria.
    Polymorphonuclear leukocyte: A type of white blood cell with a nucleus that is so deeply lobated or divided that the cell looks to have multiple nuclei. Informally called a poly.
    Polymyalgia rheumatica (PMR): A disorder of the muscles and joints of older persons characterized by pain and stiffness, affecting both sides of the body, and involving the shoulders, arms, neck, and buttock areas.
    Polymyositis: An inflammatory disease of muscle that begins when white blood cells, the immune cells of inflammation, spontaneously invade muscles, especially those closest to the trunk or torso, resulting in muscle pain, tenderness and weakness.
    Polyp: A mass of tissue that develops on the inside wall of a hollow organ, such as the colon. Polypeptide: A compound consisting of 2 or more amino acids. Amino acids make up polypeptides which make up proteins.
    Polyploid: Three or more full sets of chromosomes. A polyploid brain tumor cell might for example have 69 or 92 chromosomes.
    Polypsis of the colon: Multiple polyps with a high malignant potential in large bowel. This hereditary condition is also known as polypsis coli and Familial Adenomatous Polyposis (FAP).
    Popliteal: Refers to the back of the knee.
    Popliteal fossa: The hollow behind the knee.
    Popliteal pterygium syndrome: An inherited condition with a web behind the knee. (A pterygium is a winglike triangular membrane.)
    Pork tapeworm: Known formally as Taenia solium, contracted from undercooked or measly pork (pork infected with the larval forms of the tapeworm). Can grow to be 3-6 feet (0.9-1.8 m) long in the human intestine. Also known as the armed tapeworm and the measly tapeworm.
    Porphyria: A varied series of hereditary diseases with increased formation and excretion of chemicals called porphyrins. One type of porphyria -- acute intermittent porphyria -- may have affected members of the House of Hanover in England including Mad King George who may not have been mad but suffering attacks of porphyria.
    Portal vein: A large vein formed by the union of the splenic and superior mesenteric veins. It conveys venous blood to the liver for detoxification before being returned to the circulation via the hepatic veins.
    Port-wine stain: A mark on the skin that resembles port wine (porto) in its rich ruby red color. Due to an abnormal aggregation of capillaries, a port-wine stain is a type of hemangioma. it occurs on the face as a sign of Sturge-Weber syndrome.
    Positional cloning: Cloning a gene based simply on knowing its position in the genome without any idea of the function of that gene. Because this is the reverse of how things have been traditionally done, it has also been called reverse genetics.
    Postmature infant: A baby born 1 week (7 days) or more after the usual 9 months (280 days) of gestation.
    Postmenopausal: After the menopause. With increasing longevity, women will soon be postmenopausal for one third of their lives.
    Postremission therapy: Chemotherapy to kill leukemia cells that survive after remission induction therapy.
    Post-term infant: A baby born 2 weeks (14 days) or more after the usual 9 months (280 days) of gestation, as calculated from the Last Menstrual Period (LMP). This is an important calculation, since, if delivery is delayed 3 weeks beyond term, the infant mortality rate skyrockets to 3 times normal.
    Post-traumatic stress: A psychological disorder that develops in some individuals who have had major traumatic experiences (and, for example, have been in a serious accident or through a war). The person is typically numb at first but later has symptoms including depression, excessive irritability, guilt (for having survived while others died), recurrent nightmares, flashbacks to the traumatic scene, and overreactions to sudden noises. Post-traumatic stress became known in the 70s due to the adjustment problems of some Vietnam veterans. It was listed as a diagnostic category by the American Psychiatric Association in 1980. Although the name "post-traumatic stress" was new, the condition was not. It was known as "shell shock" in World War I and "battle fatigue" during World War II.
    Pouch, Pavlov: At different points along the dogs’ digestive tracts, the Russian physiologist Ivan Petrovich Pavlov (1848-1936) surgically created pockets ("Pavlov pouches") from which he could obtain secretions, the aim being to study the physiology of the digestive tract. He did so from the salivary glands down to the stomach, liver and pancreas with considerable success and in 1904 (the 4th year it was awarded) he received the Nobel Prize for "his work on the physiology of digestion, through which knowledge on vital aspects of the subject has been transformed and enlarged."
    Pound: A measure of weight equal to 16 ounces or, metrically, 453.6 grams. The word "pound" goes back to the Latin "pondo" which meant a "weight" (but one of only 12 ounces). The abbreviation for pound—just to confuse non-pound people—is lb. which stands for "libra" (Latin for pound).
    Power-of-attorney for health-care decision-making: See: Proxy. health care.
    Prader-Willi syndrome: A condition in children with floppiness (hypotonia), obesity, small hands and feet and mental retardation. It is due to loss of part or all of chromosome 15, specifcally the chromosome 15 from the father. The "fat and red-faced boy in a state of somnolency" described by Charles Dickens in his novel The Pickwick Papers is thought by some to have had Prader-Willi syndrome. (The same boy inspired the naming of the Pickwickian syndrome).
    Preauricular tag: Common minor anomaly, a rudimentary tag of ear tissue, often containing a core cartilage, usually located just in front of the ear (auricle). Therefore also called preauricular tag.
    Precancerous: Not cancerous, but may become cancerous with time. Precocious puberty: The onset "too early" of secondary sexual characteristics such as breast buds in girls, growth of the penis and thinning of the scrotum in boys and the appearance of pubic hair in both sexes. "Too early" is difficult to define because there is so much normal variation. However, precocious puberty is generally the onset of puberty before age 8 years in girls and age 9 years in boys. Preconceptual: Before conception (of a pregnancy).
    Preconceptual counselling: The interchange of information prior to pregnancy. Usually for pregnancy planning and care.
    Pregnancy, alcohol in: The consumption of alcohol during pregnancy carries the danger of damaging the fetus and causing fetal alcohol syndrome (FAS) or fetal alcohol effects.
    Pregnancy danger from urinary tract infection (UTI): A pregnant woman who develops a UTI should be treated promptly to avoid premature delivery of her baby and other risks such as high blood pressure. Some antibiotics are not safe to take during pregnancy. In selecting the best treatment, doctors consider various factors such as the drug’s effectiveness, the stage of pregnancy, the mother’s health, and potential effects on the fetus.
    Pregnancy, ectopic: A pregnancy that is not in the usual place and is located outside the inner lining of the uterus. A fertilized egg settles and grows in any location other than the inner lining of the uterus. The vast majority of ectopic pregnancies occur in the fallopian tube (95%), however, they can occur in other locations, such as the ovary, cervix, and abdominal cavity. An ectopic pregnancy occurs in about 1 in 60 pregnancies. A major concern with an ectopic pregnancy is internal bleeding. If there is any doubt, seek medical attention promptly.
    Pregnancy, ectopic, symptoms of: Symptoms of an ectopic pregnancy can often be vague and include vaginal bleeding, abdominal or pelvic pain (usually stronger on one side),shoulder pain, weakness, or dizziness. Weakness, dizziness, and a sense of passing out upon standing can represent serious internal bleeding, requiring immediate medical attention.
    Pregnancy danger from fifth disease: Caused by a virus known as parvovirus B 19. Symptoms include low-grade fever, fatigue, a "slapped cheeks rash," and a rash over the whole body. The illness is not serious in children. Pregnant women (who have not previously had the illness) should avoid contact with patients who have fifth disease. The virus can infect the fetus prior to birth. And, while no birth defects have been reported as a result of fifth disease, it can cause the death of the unborn fetus. The risk of fetal death is 5-10% if the mother becomes infected.
    Pregnancy planning: Pregnancy planning addresses issues of nutrition, vitamins, body weight, exercise, and potentially harmful medications and illnesses as well as immunizations and genetic counseling.
    Preleukemia: A condition in which the bone marrow does not function normally. It does not produce enough blood cells. This condition may progress and become acute leukemia. Preleukemia also is called myelodysplastic syndrome or smoldering leukemia.
    Premature contraction of the heart: When a single heartbeat occurs earlier than normal. This phenomenon can be within normal limits or represent a medically significant arrhythmia.
    Premature ventricular contractions (PVCs): Contractions of the lower chambers of the heart, the ventricles, which occur earlier than usual, because of abnormal electrical activity of the ventricles. The premature contraction is followed by a pause, as the heart electrical system "resets" itself and the contraction following the pause is usually more forceful than normal. These more forceful contractions are frequently perceived as palpitations.
    Prematurity: Historically, the definition of prematurity was 2500 grams (about 5 1/2 pounds) or less at birth. The current World Health Organization definition of prematurity is a baby born before 37 weeks of gestation, counting from the first day of the Last Menstrual Period (LMP).
    Premenstrual syndrome (PMS): A combination of emotional, physical, psychological, and mood disturbances that occur after ovulation and normally end with the onset of the menstrual flow.
    Prepuce: The fold of skin near the tip of the penis in the uncircumscribed male or the small fold of skin which partially or completely hides the clitoris in the female.
    Preventive medicine: Medicine designed to avert and avoid disease. Screening for hypertension and treating it before it causes disease is good preventive medicine. Preventive medicine is a proactive approach.
    Priapism: Abnormally persistent erection of the penis in the absence of desire. Named after Priapus, the Greek and Roman god of procreation whose nud statues were placed in fields as scarecrows where their attributes became well known.
    Primary biliary cirrhosis (PBC): A liver disease caused by an abnormality of the immune system. Small bile ducts within the liver become inflamed and obliterated. Backup of bile causes intense skin itching and yellowing of the skin (jaundice). Lack of bile decreases absorption of calcium and vitamin D, leading to osteoporosis. Cirrhosis (scarring of the liver) develops over time.
    Primary care: The "medical home" for a patient, ideally providing continuity and integration of health care. All family physicians and most pediatricians and internists are in primary care. The aims of primary care are to provide the patient with a broad spectrum of care, both preventive and curative, over a period of time and to coordinate all of the care the patient receives.
    Primary dentition: The set of 20 first (deciduous) teeth. The primary dentition is as opposed to the secondary (permanent) dentition. At birth, both sets of dentition are evident by X-ray.
    Primary sclerosing cholangitis (PSC): A condition found in association with ulcerative colitis in which the large bile ducts outside the liver become inflamed and obstructed leading to frequent infections and jaundice, causing cirrhosis and sometimes creating the need for liver transplantation.
    Primary teeth: The first teeth which are shed and replaced by permanent teeth. The first primary tooth comes in (erupts) at about 6 months of age and the 20th and last one erupts at around 2 1/2 years of age. The primary teeth are replaced usually beginning at about age 6. Also called baby teeth, milk teeth, temporary teeth or deciduous teeth. (In Latin, decidere means to fall off or be shed, like leaves from a tree).
    Primitive neuroectodermal tumors: A type of brain tumor. Prenatal diagnosis: Diagnosis before birth. Methods for prenatal diagnosis include ultrasound (of the uterus, placenta and developing fetus), chorionic villus sampling (CVS) to obtain tissue for chromosome or biochemical analysis, amniocentesis to obtain amniotic fluid for the analysis of chromosmes, enzymes, DNA, etc. A growing number of birth defects and diseases are now amenable to prenatal diagnosis. Also called antenatal diagnosis.
    Prions: A new type of disease-causing agent, neither bacterial nor fungal nor viral, containing no genetic material, a prion is a protein that occurs normally in a harmless form in the brain. (The word prion was coined from PRoteinaceous + Infectious + the suffix ON meaning a subatomic particle, like a proton or neutron). By folding into an aberrant shape, the normal prion turns into a rogue agent. It then coopts other normal prions to become rogue prions that slowly destroy brain cells until the ravaged brain resembles a sponge. Prions have been held responsible for a number of degenerative brain diseases including mad cow disease, Creutzfeld-Jacob disease, fatal familial insomnia, kuru (a disease transmitted by cannibalism), an unusual form of hereditary dementia (Gertsmann-Straeussler-Scheinker disease) and some cases of Alzheimer's disease. Dr. Stanley B. Prusiner received the 1997 Nobel Prize in physiology or Medicine for his discovery of prions..
    Private mutation: A rare mutation found usually only in a single family or a small population. It is like a privately printed book.
    Pro-: Prefix (from both Greek and Latin) with many meanings including "before, in front of, preceding, on behalf of, in place of, and the same as." Used as a word, pro of course means professional and, in medicine, it is short for prothrombin.
    Probability: Medicine is to a significant degree based on probability theory. Probability in this context is the likelihood of something happening. The abbreviation for probability is P. For example, P<0.05 indicates that the probability of something occurring by chance alone is less than 5 in 100, or 5%. As a matter of fact, P<0.05 is usually taken as the level of biologic significance where a result may be considered meaningful.
    Proband: The family member through whom a family medically comes to light. The proband might for example be a baby with Down syndrome. The proband may also be called the index case, propositus (if male) or proposita (if female).
    Probe: (1) In surgery, a probe is a slender flexible rod with a blunt end used to explore, for example, an opening to see where it goes. (2) In molecular genetics, a probe is a labeled bit of DNA or RNA used to find its complementary sequence or locate a particular clone like homing in on a needle in a haystack.
    PROC: Protein C
    Process: In anatomy, a process is a projection from a structure. From the Latin pro-, forward + ceder, to go + a going forward. The process of the mandible is the part of the lower jaw that projects forward.
    Proctology: From the Greek proktos meaning the anus or hindparts, proctology deals with anorectal disorders.
    Proctosigmoidoscopy: An examination of the rectum and the lower part of the colon using a thin, lighted instrument called a sigmoidoscope.
    Product, gene: The RNA or protein that results from the expression of a gene. The amount of gene product is a measure of the degree of gene activity.
    Progeria: A disorder characterized by premature aging.
    Prognathism: An overly prominent jaw.
    Progesterone: A female hormone, progesterone is the principal progestational hormone. Progestational hormones prepare the uterus (the womb) to receive and sustain the fertilized egg.
    Prognosis: The probable outcome or course of a disease; the patient's chance of recovery.
    Prokaryote: Cell lacking a discrete nucleus and other special subcellular compartments. Bacteria and viruses are prokaryotes. Humans are not prokaryotes, but rather eukaryotes.
    Promoter: In molecular biology, a site on DNA to which the enzyme RNA polymerase can bind and initiate the transcription of DNA into RNA.
    Pronation: Rotation of the arm or leg inward. In the case of the arm, the palm of the hand will face posteriorly.
    Prone: Lying face downward.
    Pronucleus: A cell nucleus with a haploid set of chromosomes (23 chromosomes in humans) resulting from meiosis (germ-cell division). The male pronucleus is the sperm nucleus after it has entered the ovum at fertilisation but before fusion with the female pronucleus. Similarly, the female pronucleus is the nucleus of the ovum before fusion with the male pronucleus.
    Prophylactic cranial irradiation: Radiation therapy to the head to prevent cancer from spreading to the brain.
    Prophylaxis: The prevention of disease.
    Propositus: The family member through whom a family medically comes to light. Also called the proband or index case. The feminine of propositus is proposita.
    Propylthiouracil (PTU): A drug that blocks the production of thyroid hormones by the thyroid gland. PTU is used to treat hyperthyroidism, to reduce the excessive thyroid activity before surgery and to treat and maintain patients not having surgery.
    Prostate acid phosphatase: An enzyme produced by the prostate that is elevated in some patients with prostate cancer.
    Prostate cancer: An uncontrolled (malignant) growth of cells in the prostate gland which is located at the base of the urinary bladder and is responsible for helping control urination as well as forming part of the semen. Prostate cancer is the second leading cause of death of males in the U.S.
    Prostate gland: A gland in the male reproductive system just below the bladder. It surrounds part of the urethra, the canal that empties the bladder.
    Prostate specific antigen: A protein that is elevated in some patients with prostate cancer.
    Prostatectomy: The surgical removal of the prostate gland.
    Prosthesis: An artificial replacement of a part of the body, such as a tooth, a facial bone, the palate, or a joint.
    Prostatitis: Inflammation of the prostate gland.
    Prosthodontist: A dentist with special training in making replacements for missing teeth or other structures of the oral cavity to restore the patient's appearance, comfort, and/or health.
    Protease: An enzyme that can split a protein into peptides (from whence the protein was originally created).
    Protease inhibitor: An agent that can keep a protease from working and splitting a protein into peptides. Protease inhibitors are used in HIV/AIDS treatment.
    Protein C: A vitamin K-dependent protein in plasma that enters into the cascade of biochemical events leading to the formation of a clot.
    Protein C deficiency: Protein C is a protein in plasma that enters into the cascade of biochemical events leading to the formation of a clot. Deficiency of protein C results in thrombotic (clotting) disease and excess platelets with recurrent thrombophlebitis (inflammation of the vein that occurs when a clot forms). The clot can break loose and travel through the blood stream (thromboembolism) to the lungs causing a pulmonary embolism, brain causing a stroke (cerebrovascular accident), heart causing an early heart attack, skin causing what in the newborn is called neonatal purpura fulminans, the adrenal gland causing hemorrhage with abdominal pain, abnormally low blood pressure (hypotension), and salt loss. Protein C deficiency is due to possession of one gene (heterozygosity) in chromosome band 2q13-14. The possession of two such genes (homozygosity) is usually lethal.
    Protein-losing enteropathy: Condition in which plasma protein is lost to excess into the intestine. This can be due to diverse causes including gluten enteropathy, extensive ulceration of the intestine, intestinal lymphatic blockage, and infiltration of leukemic cells into the intestinal wall.
    Protein malnutrition: Children are particularly prone to develop protein malnutrition. To grow, children have to consume enough nitrogen-containing food (protein) to maintain a positive nitrogen balance whereas adults need only be in nitrogen equilibrium.
    Protein-calorie malnutrition: Severe deficiency of protein + inadequate caloric intake = kwashiorkor.
    Proteinuria: Excess protein in the urine. Some protein is normal in the urine. But too much means protein is leaking through the kidney, most often through the glomeruli.
    Proteus syndrome: A disturbance of cell growth including benign tumors under the skin, overgrowth of the body, often more on one side than the other (hemihypertrophy), and overgrowth of fingers (macrodactyly). The syndrome is named after the Greek god Proteus the polymorphous who could change his appearance. The "elephant man" (John MerricK) of 19th century England who was thought to have had neurofibromatosis probably had Proteus syndrome.
    Proto-oncogene: A normal gene involved in cell division or proliferation which, when altered by mutation, becomes an oncogene that can contribute to cancer.
    Prothrobin: A coagulation factor needed for the normal clotting of blood. In the cascade of events leading to the final clot, prothrombin precedes thrombin (and so is a precursor to thrombin). Also called thrombinogen. Prothrombin time: A clotting test, a test done to test the integrity of part of the clotting scheme. Familiarly called the "pro time," the test is the time needed for clot formation after a substance called thromboplastin (+ calcium) has been added to plasma.
    Pro time: Prothrombin time.
    Protozoa: A single-cell organism that can only divide within a host organism. Malaria is caused by a protozoa: Plasmodium. Other protozoan parasites Giardia and Toxoplasma.
    Proximal: The nearer of two or more whatevers. For example, the proximal end of the femur is part of the hip joint. The opposite of proximal is distal.
    Proxy, health care: A health care proxy is one form of advance medical directive. Advance medical directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There are two basic forms of advance directives:
    (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for health-care decision-making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society).
    Pruritic: Medicalese for itchy. A scab may be pruritic.
    Pruritis: Itching. Pruritis can result from drug reaction, food allergy, kidney or liver disease, cancers, parasites, aging or dry skin, contact skin reaction, such as poison ivy, and for unknown reasons.
    Pruritus: Itching. Poison ivy causes intense pruritus.
    Pseudodementia: A severe form of depression resulting from a progressive brain disorder in which cognitive changes mimic those of dementia.
    Pseudogout: Inflammation of the joints caused by deposits of calcium pyrophosphate crystals, resulting in arthritis, most commonly of the knees, wrists, shoulders, hips, and ankles, usually affecting only one or a few joints at a time. True gout is due to a different type of crystal formed by the precipitation of uric acid.
    Pseudomembranous colitis: Severe inflammation of the inner lining of the colon. Pseudomembranous colitis is characterized by pus and blood in the stool and often caused by antibiotics.
    Pseuodoparalysis, spastic: Better known as Creutzfeldt-Jakob disease (CJD). A dementing disease of the brain. It is believed due to an unconventional (not a bacteria or virus), transmissible agent called a prion. Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome and Jakob-Creutzfeldt disease.
    Pseudorubella: Synonymous with Roseola infantum, a viral disease of infants sudden onset of high fever which lasts several and young children with days and then suddenly subsides leaving in its wake a fine red rash. The causative agent is herpesvirus type 6 so the disease is known as Sixth Disease. Also as Exanthem subitum (sudden rash), roseola, roseola infantilis.
    Pseudoxanthoma elasticum: (abbreviated PXE), a rare disorder of degeneration of the elastic fibers with tiny areas of calcification in the skin, back of the eyes (retinae), and blood vessels. PXE is inherited from the parents, either as an autosomal recessive or as an autosomal dominant trait. PXE typically causes yellow-white small raised areas in the skin folds, often appearing in the second or third decades of life. These skin abnormalities frequently appear on the neck, armpits, and other areas that bend a great deal (referred to as flexure areas). The face is not affected by PXE. The doctor can often see abnormalities in the back of the eye (retinae) called angioid streaks, which are tiny breaks in the elastin-filled tissue there. These eye abnormalities can lead to blindness. Other areas that can be affected in PXE include the heart which can be affected by atherosclerosis and mitral valve prolapse. Small blood vessels are abnormally fragile in patients with PXE because the blood vessel walls contain elastin and are weakened. This can lead to abnormal bleeding in such areas as the bowel and, very rarely, the uterus. Impairment of circulation to the legs can lead to pains in the legs while walking (claudication).
    Psittacosis (parrot fever): An infectious disease due to a bacteria (Chlamydia psittaci) contracted from psittacine birds, especially caged birds like parrots but also in turkey processing plants. The name comes from the Greek psittakos meaning parrot.
    Psoriasis: A reddish, scaly rash often located over the surfaces of the elbows, knees, scalp, and around or in the ears, navel, genitals or buttocks. Approximately 10-15% of patients with psoriasis develop joint inflammation (inflammatory arthritis).
    Psoriatic arthritis: Joint inflammation associated with psoriasis. Psoriatic arthritis is a potentially destructive and deforming form of arthritis that affects approximately 10% of persons with psoriasis.
    Psyche: The mind.
    Psychiatrist: A physician specializing in the prevention, diagnosis, and treatment of mental illness.
    Psychogenic: Caused by the mind or emotions.
    Psychologist: A professional concerned with the mind and behavior. Training in psychology leads to the masters and doctor of philosophy (PhD) degrees.
    Psychosis: In the general sense, a mental illness that markedly interferes with a person's capacity to meet life's everyday demands. In a specific sense, it refers to a thought disorder in which reality testing is grossly impaired.
    Psychosis, schizophrenia: The most chronic and disabling of the major mental illnesses. Schizophrenia may be one disorder, or it may be many disorders, with different causes. Because of the disorder's complexity, few generalizations hold true for all people who are diagnosed as schizophrenic.
    Psychosomatic illness: The mind influences the body to create or exacerbate illness.
    PTCA (Angioplasty): Procedure with a balloon-tipped catheter to enlarge a narrowing in a coronary artery. PTCA stands for Percutaneous Transluminal Coronary Angioplasty.
    Pterygium: A winglike triangular membrane. Although a pterygium can be anywhere (including behind the knee), it commonly refers to an winglet (of the conjunctiva) extending across the white of the eye toward the inner corner of the eye, caused environmentally by prolonged exposure of the eyes to wind and weather or familially by a single gene.
    Ptosis: Downward displacement. Ptosis of the eyelids is drooping of the eyelids.
    PTU: Propylthiouracil, an antithyroid medication.
    Pubarche: Just as menarche means the time when menstruation begins, pubarche indicates when pubic hair begins.
    Puberty: Adolescence. The word puberty derives from the Latin pubertas: coming to the age of manhood.
    Pubis: The front center portion of the pelvis.
    Public health: Medicine concerned with the health of the community as a whole. Community health.
    Pubic symphysis: The joint between the pubic bones at the front of the pelvis.
    Pulmonary: Having to do with the lungs. (The word comes from the Latin pulmo for lung).
    Pulmonary edema: Fluid in the lungs.
    Pulmonary embolism: Sudden closure of a pulmonary artery or one of its branches by a bloodborne clot or foreign material that plugs the vessel. Pulmonary embolus: A blood clot within the lung's pulmonary artery. An embolus causes an embolism. In this case, the embolus, a clot or foreign material, has been carried through the blood into the pulmonary artery or one of its branches, plugging the vessel. (Embolus is from the Greek embolos for plug or wedge)
    Pulmonary hypertension: High blood pressure in the pulmonary arteries. Normally, the pressure in the pulmonary arteries is low (compared to that in the aorta). Pulmonary hypertension can irrevocably damage the lungs.
    Pulmonary insufficiency: Pulmonary here refers to the valve between the right ventricle of the heart and the pulmonary artery. If this valve is insufficient (incompetant) in its performance, blood sloshes back from the pulmonary artery into the right ventricle.
    Pulmonary stenosis: The pulmonary valve is too tight so that the flow of blood from the right ventricle of the heart into the pulmonary artery is impeded.
    Pulmonary valve: One of the four valves in the heart, the pulmonary valve stands at the opening from the right ventricle in the pulmonary artery trunk. It lets blood head in the right direction (toward the lungs) and keeps it from sloshing back from the pulmonary artery into the heart.
    Pulse: The pulse is the rhythmic dilation of an artery resulting from beating of the heart. It is often measured by feeling the arteries of the wrist The word pulse is from the Latin pulsus meaning, among other things, a beating. The ancient Greeks and Romans recognized that the pulse in arteries (as at the wrist) was connected with the beating of the heart.
    Pump-oxygenator: A machine that does the work both of the heart (pump blood) and the lungs (oxygenate the blood). Used, for example, in open heart surgery. Blood returning to the heart is diverted through the machine before returning it to the arterial circulation. Also called a heart-lung machine.
    Punch biopsy: A punch is an instrument for cutting and removing a disk of tissue. A punch biopsy of the skin may for example be done to make the diagnosis of a malignancy.
    Puncture wound: An injury from piercing or penetrating with a pointed object. Any puncture wound through tennis shoes (as with a nail) has a high risk of infection because the foam in tennis shoes can harbor a bacteria (Pseudomonas).
    Pupil: The opening of the iris. The pupil may appear to open (dilate) and close (constrict) but it is really the iris that is the prime mover; the pupil is merely the absence of iris.
    Purine: One of the two classes of bases in DNA and RNA. The purine bases are guanine (G) and adenine (A). Uric acid, the offending substance in gout, is a purine end-product.
    Purpura: A hemorrhage area in the surface of the skin. The appearance of an individual area of purpura varies with the duration of the lesions. Early purpura is red and becomes darker, then purple, and brown-yellow as it fades.
    Purpura, anaphylactoid: See Purpura, Henoch-Schonlein.
    Purpura, Henoch-Schonlein (HSP): HSP is a form of blood vessel inflammation, a vasculitis that affects small arterial vessels in the skin (capillaries) and the kidneys. HSP results in skin rash associated with joint inflammation (arthritis) and cramping pain in the abdomen. HSP frequently follows a bacterial or viral infection of the throat or breathing passages and is an unusual reaction of the body’s immune system to this infection. HSP occurs most commonly in children. HSP is generally a mild illness that resolves spontaneously, but sometimes it can cause serious problems in the kidneys and bowels. Treatment is directed toward the most significant area of involvement. Joint pain can be relieved by antiinflammatory medications, such as aspirin or ibuprofen. Some patients can require cortisone-related medications, such as prednisone, especially those with significant abdominal pain or kidney disease. Also known as anaphylactoid purpura.
    Pus: A thick whitish-yellow fluid which results from the accumulation of white blood cells (WBCs), liqified tissue and cellular debris. Pus is commonly a site of infection or foreign material in the body.
    PVC: Abbreviation for premature ventricular contraction.
    PXE: Abbreviation for pseudoxanthoma elasticum, a rare disorder of degeneration of the elastic fibers with tiny areas of calcification in the skin, back of the eyes (retinae), and blood vessels. PXE is inherited from the parents, either as an autosomal recessive or as an autosomal dominant trait. PXE typically causes yellow-white small raised areas in the skin folds, often appearing in the second or third decades of life. These skin abnormalities frequently appear on the neck, armpits, and other areas that bend a great deal (referred to as flexure areas). The face is not affected by PXE. The doctor can often see abnormalities in the back of the eye (retinae) called angioid streaks, which are tiny breaks in the elastin-filled tissue there. These eye abnormalities can lead to blindness. Other areas that can be affected in PXE include the heart which can be affected by atherosclerosis and mitral valve prolapse. Small blood vessels are abnormally fragile in patients with PXE because the blood vessel walls contain elastin and are weakened. This can lead to abnormal bleeding in such areas as the bowel and, very rarely, the uterus. Impairment of circulation to the legs can lead to pains in the legs while walking (claudication).
    Pycnodysostosis: An inherited disorder of the bone. that causes short stature and abnormally dense brittle bones. Due to a defect in an enzyme: cathepsin K. The French artist Toulouse-Lautrec is thought to have pycnodysostosis. Also spelled pyknodysostosis with a "k".
    Pyelo: Short for pyelonephritis.
    Pyelogram: X-ray study of the kidney especially showing the pelvis (urine-collecting basin) of the kidney and the ureter.
    Pyelonephritis: Bacterial infection of the kidney. Pyelonephritis can be acute (sudden) or chronic (slow, subtle, and stubborn). It is most often due the ascent of bacteria from the bladder up the ureters to infect the kidneys.
    Pyloric stenosis: Narrowing (stenosis) of the outlet of the stomach so that food cannot pass easily from it into the duodenum, resulting in feeding problems and projectile vomiting. The obstruction can be corrected by a relatively simple surgical procedure.
    Pylorus: The outlet of the stomach.
    Pyoderma gangrenosum: An ulcerating condition of skin resulting in heaped borders with a typical appearance. Pyoderma gangrenosum appears to be mediated by the immune system, but the exact cause is unknown. The lesion(s) usually begin as a soft nodule on the skin which proceeds to ulcerate. The ulcer enlarges and the skin at the edge is purple-red. Ulcers can become quite large. This condition is associated with several other diseases, some of which are ulcerative colitis, Crohn’s disease, rheumatoid arthritis, leukemia, and cryoglobulinemia. Pyoderma gangrenosum is usually responsive to corticosteroids.
    Pyrimidine: One of the two classes of bases in DNA and RNA. The pyrimidine bases are thymine (T) and cytosine (C) in DNA and thymine (T) and uracil (U) in RNA.

    Pyuria: Pus in the urine. Pyuria is a sign of inflammation often related to infection.
  • q arm of a chromosome: The long arm of a chromosome. All human chromosomes have 2 arms: the short (p) arm and the long (q) arms.
    q in population genetics: The frequency of the less common of two different alternative (allelic) versions of a gene. (The frequency of the more common allele is p).
    Q bands: The alternating bright and dull fluorescent bands seen on chromosomes under ultraviolet light after the chromosomes are stained with quinacrine. The Q stands for Quinacrine, an agent used as an antimalarial agent and, in the laboratory, as a fluorescent dye.
    q.d.: Seen on a prescription, q.d. (or qd) means one a day (from the Latin quaque die).
    Q-fever: An acute (abrupt-onset), self-limited febrile illness first reported in 1935 in Queensland, Australia. The Q is said not to be for Queensland, but for Query since the cause of the disease was long a query (question mark). It is now known to be due to Coxiella burnetti, a rickettsia (a peculiar group of bacteria). Aside from sudden onset of fever, there is headache, malaise, and pneumonia (interstitial pneumonitis) but no rash.
    q.i.d.: Seen on a prescription, q.i.d. (or qid) means 4 times a day (from the Latin quater in die).
    q.h.: Abbreviation for "every hour." On a prescription or doctor's hospital orders, q.h. means every hour. Also written qh (without the periods). From the Latin quaque die.
    q.n.s.: On a lab report, q.n.s. (or qns or QNS) means Quantity Not Sufficient. Not enough blood, urine or whatever to do the test.
    QRS complex: The deflections in an electrocardiographic (ECG or EKG) tracing that represent the ventricular activity of the heart.
    Quackery: Deliberate misrepresentation of the ability of a substance or device for the prevention or treatment of disease. We may think that the day of patent medicines is gone but look around you and you will see them still. They appeal to our desire to believe that every disease is curable or at least treatable. Quackery also applies to persons who pretend to be able to diagnose or heal people but are unqualified and incompetant.
    Quadrant: A quarter. For example, the liver is in the right upper quadrant of the abdomen.
    Quadriceps: Any four-headed muscle but usually refers to the quadriceps muscle of the thigh, the large muscle that comes down the femur (the bone of the upper leg), over the patella (the kneecap) and anchors into the top of the tibia (the big bone in the lower leg). The function of the quadriceps is to straighten out (extend) the leg. For those who are into Latin, this muscle's name is musculus quadriceps femoris. For those who prefer nicknames, it is the quad.
    Quadriparesis: Weakness of all four limbs, both arms and both legs, as for example from muscular dystrophy.
    Quadriplegia: Paralysis of all four limbs, both arms and both legs, as from a high spinal cord accident or stroke.
    Qualitative: Having to do with quality. In contrast to quantitative (which pertains to quantity, the amount).
    Quantitative: Having to do with quantity or with the amount.
    Quarantine: The period of isolation decreed to control the spread of infectious disease. Before the era of antibiotics and the like, quarantine as one of the few available means for halting the reach of infectious diseases. The word quarantine comes from the Latin quadraginta meaning forty. This was probably because it was known that the incubation period of most infectious diseases was less than 40 days.
    Quasi-: Prefix meaning seemingly.
    Quasidiploid: Seems to have the usual two full sets of 23 chromosomes and so to have a normal chromosome complement, but on closer examination, this is not so. Many malignant cells are quasidiploid. Also called pseudodiploid.
    Quasidominant: Pattern of inheritance that seems due to a dominant trait but, in fact, is due to the mating of a person who has a recessive disorder (with 2 copies of a gene causing the disease) with someone who is an asymtomatic carrier ( and has 1 copy of the same gene buut no symptoms).
    Queensland tick typhus: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.
    Quickening: This apt word refers to the miraculous moment during pregnancy when the baby is first felt to move. Quickening has been used in this sense in the English language since 1530.
    Quiescent: Inactive, resting. Tuberculosis might be quiescent (inactive).
    Quinacrine: An antimalarial drug and, in cytogenetics, a fluorescent dye used to stain chromosomes. The Y chromosome stains brilliantly with quinacrine.
    Quincke's disease: This is angioneurotic edema (or angioedema), a form of localized swelling of the deeper layers of the skin and fatty tissues beneath the skin. Hereditary angioneurotic edema (or hereditary angioedema) is a genetic form of angioedema. Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks.
    Quinine: A classic antimalarial agent, quinine took its name from the Peruvian Indian kina meaning bark of the tree (they called it the fever tree), the cinchona tree from which quinine was first gained.
    Quinsy: Not a TV detective but an old word for a peritonsillar abscess.
    Quintan fever: A louse-borne disease first recognized in the trenches of World War I (and so called trench fever), again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Quintan means recurring every 5 days and refers to the fever. Also called five-day fever. Other names include Wolhynia fever, shin bone fever, Meuse fever, His’ disease, His-Werner disease, Werner-His disease.
    Quotidian: Recurring each day, as in a fever that returns every day. From the Latin quotidianus for daily. (In French, the noun quotidien is a daily newspaper.

    Quotient: The result of mathematical division. The I.Q. (Intelligence Quotient) is arrived at by dividing the person's mental age (as determined on the Binet test) by the person's chronologic age and multiplying by 100. So if a child scores at the 8-year old level but is only 6, the I.Q. is 8/6 X 100=125.
  • R: Commonly used abbreviation for respiration(s). For example, in a medical chart, you might see scrawled "BP90/60 T98.6 HR 60/reg R15", which is short hand signifying that the blood pressure is 90/60 mm Hg, the temperature (T) is 98.6 degrees Fahrenheit, the heart rate (HR) is 60/min and regular, and the respirations ® 15/min. (This example would be entirely normal for an adult or older child). 
    r: Symbol for a ring chromosome, a structurally abnormal chromosome in which the end of each chromosome arm has been lost and the broken arms have been reunited in ring formation.
    Rabid: Having contracted the rabies virus. (Whereas a sports fan can be rabid without being physically sick, in medicine a rabid individual has rabies.)
    Rabies: Virus disease of warmblooded animals transmitted to people by a bite (or other means). Animals capable of carrying rabies include dogs, bats, cats, racoons and skunks. In Latin, rabies means madness or rage.
    Rad: A unit of energy. A rad is like a roentgen ® but is based on absorbed energy from an ionizing or nonionizing source.
    Radial: In anatomy, radial pertains to the radius, the smaller of the two bones on the thumb's side of the forearm. (The bigger one is the ulna). The word radius comes unchanged from the Latin meaning a spoke in a wheel which this bone was thought to resemble. The word radiation is derived from the same Latin word, radius.
    Radial aplasia-thrombocytopenia syndrome: Aplasia (absence) of the Radius (the long bone on the thumb-side of the forearm) and Thrombocytopenia (low blood platelets) are key features characterizing this syndrome. There is phocomelia (flipper-limb) with the thumbs always present. The fibula (the smaller bone in the lower leg) is often absent. The risk of bleeding from too few platelets is high in early infancy but lessens with age. The condition is inherited in an autosomal recessive trait with one gene (on a non-sex chromosome) coming from each parent to the child affected with the disease. Alternative names include thrombocytopenia-absent radius syndrome, TAR syndrome, and tetraphocomelia-thrombocytopenia syndrome.
    Radiation: The word radiation is derived from the Latin word radius meaning a spoke in a wheel. The same Latin word radius was given by the Romans to the smaller of the two bones in the forearm since it was thought to look like a spoke in a wheel.
    Radiation fibrosis: The formation of scar tissue as a result of radiation therapy to the lung.
    Radiation oncologist: A doctor who specializes in using radiation to treat cancer.
    Radiation therapy: Radiation therapy is the use of special high energy x-ray beams to kill rapidly growing cells, such as cancer cells. It is a generally a painless treatment and is given in an outpatient setting without the need for hospitalization.
    Radical cystectomy: Surgery to remove the bladder as well as nearby tissues and organs.
    Radical, free: In biochemistry, it is a group of atoms bonded together into an entity that is extremely reactive and shortlived. (A free radical is not a political extremist on parole.)
    Radical mastectomy, modified: Breast cancer treatment involving removal of the breast, lymph nodes (the "glands") in the armpit and associated skin and subcutaneous tissue. It differs from total radical mastectomy in that the pectoral (chest) muscles are preserved.
    Radical mastectomy, total: Breast cancer treatment involving removal of the breast, the pectoral (chest) muscles, lymph nodes (the "glands") in the armpit and associated skin and subcutaneous tissue.
    Radical surgery: Surgery designed to remove all possible diseased tissue, for example, all possible tumor tissue.
    Radicle: Radicle is the diminutive derived from the Latin radix meaning root so it is therefore a little root. A nerve radicle is the smallest extension of a nerve.
    Radiculitis: Inflammation of the root of a spinal nerve. The Latin radix means root.
    Radioactive: Giving off radiation.
    Radioactive iodine: Iodine that gives off radiation. See radioiodine.
    Radioallergosorbent test (RAST): An allergy test done on a sample of blood. The aim with RAST, as with skin tests, is to check for allergic sensitivity to specific substances. RAST stands for RadioAllergoSorbent Test.
    Radiograph: Medical term for an X-ray. A film produced by X-ray.
    Radiography: Film records (radiographs) of internal structures of the body. Radiography is made possible by X-rays (or gamma rays) passing through the body to act on a specially sensitized film.

    Radioimmunoassay: A very sensitive, specific laboratory test (assay) using radiolabeled (and unlabeled) substances in an immunological (antibody-antigen) reaction.
    Radioinsensitive: Not sensitive to X-rays and other forms of radiant energy. For example, a tumor may unfortunately be radioinsensitive. The opposite of radiosensitive.
    Radioiodine: A radioactive isotope of iodine. (An isotope is an alternate version of a chemical element that has a different atomic mass). Radioiodine can be used in diagnostic tests as well as in radiotherapy of the thyroid. For hyperthyroidism, radioiodine is administered in capsule form on a one-time basis. It directly radiates thyroid tissues thereby destroying them. It takes 8-12 weeks for the thyroid to become euthyroid (normal) after treatment. The majority of patients undergoing this treatment eventually become hypothyroid, which is easily treated using thyroid hormones (levothyroxine). Radioiodine is contraindicated during pregnancy and breast feeding.
    Radioisotope: A radioactive isotope. (An isotope is an alternate version of a chemical element that has a different atomic mass).
    Radiologic: Having to do with radiology.
    Radiology: The science of radiation, both ionizing (like X-ray) and nonionizing (like ultrasound), applied to the diagnosis and treatment of disease. Radiology is also known as roentgenology after Wilhelm Conrad Roentgen who discovered X-rays in 1895.
    Radiolucent: X-rays shine right through things that are radiolucent ( lucere in Latin means to shine). Radiolucent structures appear black on exposed X-ray film.
    Radiopaque: X-rays cannot penetrate things that are radiopaque (opaque to X-ray). Radiopaque structures appear white on exposed X-ray film.
    Radionuclide scan: An exam that produces pictures (scans) of internal parts of the body. The patient is given an injection or swallows a small amount of radioactive material. A machine called a scanner then measures the radioactivity in certain organs.
    Radiosensitive: Sensitive to X-rays and other forms of radiant energy. For example, a tumor may be radiosensitive. The opposite is radioinsensitive.
    Radiotherapy: The treatment of disease with ionizing radiation. Synonymous with radiation therapy.
    Radium: The celebrated radioactive element discovered by Marie and Pierre Curie in 1898.
    Radius: In anatomy, the radius is the smaller of the the two bones on the thumb's side of the forearm. (The bigger one is the ulna). The word radius comes unchanged from the Latin meaning a spoke in a wheel which this bone was thought to resemble. The word radiation is derived from the same Latin word, radius.
    Radon: A radioactive element formed as a gas during the breakdown of radium.
    Ragweed: Any of a number of weedy composite herbs that produce a pollen that is a frequent cause of allergies. Of all allergy sufferers in the United States, 75% are allergic to ragweed.
    Rale: A type of abnormal lung sound heard through a stethescope. Rales may be sibilant (whistling), dry (crackling) or wet (more sloshy) depending on the amount and density of fluid refluxing back and forth in the air passages. The word rale is a straight steal from the French rale (minus the circumflex accent over the a). In French, a rale was originally restricted to the death rattle (le rale de mort). After Laennec invented the stethescope in France in 1815, he borrowed the word rale to apply it to the less ominous, albeit still abnormal, lung sounds he heard through his newfangled instrument.
    Ramus: A standard medical dictionary contains over 13 pages full of entries to the word ramus. Why? Because ramus in Latin means a branch and all sorts of anatomic items such as blood vessels and nerves quite naturally have branches. So, for example, medicine is plagued with the likes of the ramus acetabularis arteriae circumflexae femoris medialis which is simply the branch of an artery that goes to the acetabulum (the socket) of the hip joint.
    Ramus of the mandible: The mandible (the lower jaw bone) is shaped like a horseshoe. The back parts of the horseshoe that stick up are the two ramuses, or more properly, the rami of the mandible.

    Random mating: Totally haphazard mating with no regard to the genetic makeup (genotype) of the mate so that any sperm has an equal chance of fertilizing any egg. This rarely, if ever, occurs but the concept is impoortant in population genetics. Also called panmixus.
    Range: In medicine (and statistics), the range is the difference between the lowest and highest numerical values. For example, if premature infants are born weighing 2, 3, 4, 4, and 5 pounds, the range of their birth weights is 2-5 pounds.
    Range, normal: Normal results can fall outside the normal range. By convention, the normal range is set to cover ninety-five percent (95%) of values from a normal population. Five percent (5%) of normal results therefore fall outside the normal range.
    Range of motion: The range through which a joint can be moved, usually its range of flexion and extension. Due to an injury, the knee may for example lack 10 degrees of full extension.
    Rash: Breaking out (eruption) of the skin. Medically, a rash is referred to as an exanthem.
    RAST: An allergy test done on a sample of blood. The aim with RAST, as with skin tests, is to check for allergic sensitivity to specific substances. RAST stands for RadioAllergoSorbent Test.
    Rat-flea typhus: Murine typhus, an acute infectious disease with fever, headache, and rash, all quite similar to, but milder than, epidemic typhus, caused by a related microoganism, Rickettsia typhi (mooseri), transmitted to humans by rat fleas (Xenopsylla cheopis). The animal reservoir includes rats, mice and other rodents. Murine typhus occurs sporadically worldwide but is more prevalent in congested rat-infested urban areas. Also known as endemic typhus and urban typhus of Malaya.
    Rate, basal metabolic: A measure of the rate of metabolism. For example, someone with an overly active thyroid will have an elevated basal metabolic rate.
    Rate, birth: The birth rate is usually given as the number of live births divided by the average population (or the population at midyear). This is termed the crude birth rate. In 1995, for example, the crude birth rate per 1,000 population was 14 in the United States, 16.9 in Australia, etc.

    Rate, death: The number of deaths in the population divided by the average population (or the population at midyear) is the crude death rate. In 1994, for example, the crude death rate per 1,000 population was 8.8 in the United States, 7.1 in Australia, etc. A death rate can also be tabulated according to age or cause.
    Rate, erythrocyte sedimentation: A sedimentation rate, or "sed rate", is a blood test that detects and is used to monitor inflammation activity. It is measured by recording the rate at which red blood cells (RBCs) sediment in a tube over time. It increases (the RBCs sediment faster) with more inflammation.
    Rate, fetal mortality: The ratio of fetal deaths divided by the sum of the births (the live births + the fetal deaths) in that year. In the United States, the fetal mortality rate plummeted from 19.2 per 1,000 births in 1950 to 9.2 per 1,000 births in 1980.
    Rate, heart: Number of heart beats per minute. The normal resting adult heart beats regularly at an average rate of 60 times per minute. (Young children’s hearts beat faster). The speed of the heartbeat (heart rate) is governed by the speed of electrical signals from the pacemaker of the heart, the SA node, located in the right atrium (upper chamber of the heart). The electrical signals from the SA node travel across the atria and cause these two upper heart chambers to contract, delivering blood into the lower heart chambers, the ventricles. The electrical signals then pass through the AV node to reach the ventricles. Electrical signals reaching the ventricles cause these chambers to contract, pumping blood to the rest of the body, generating the pulse. During rest, the speed of electrical signals originating from the SA node is slow, so the heart beats slowly. During exercise or excitement, the speed of signals from the SA node increases, and the heartbeat quickens.
    Rate, infant mortality: The number of children dying under a year of age divided by the number of live births that year. The infant mortality rate in the United States, which was 12.5 per 1,000 live births in 1980, fell to 9.2 per 1,000 live births in 1990.
    Rate, maternal mortality: The number of maternal deaths related to childbearing divided by the number of live births (or by the number of live births + fetal deaths) in that year. The maternal mortality rate in the United States in 1993 (and 1994) was 0.1 per 1,000 live births, or 1 mother dying per 10,000 live births.
    Rate, neonatal mortality: The number of children dying under 28 days of age divided by the number of live births that year. The neonatal mortality rate in the United States, which was 8.4 per 1,000 live births in 1980, declined to 5.8 per 1,000 live births in 1990.
    Rate, pulse: The pulse rate is most often taken at the wrist. It measures the number of pulsations in the radial artery each minute.

    Rate, respiratory: The number of breaths per minute (or, more formally, the number of movements indicative of inspiration and expiration per unit time). In practice, the respiratory rate is usually determined by counting the number of times the chest rises (or falls) per minute. By whatever means, the aim is to determine if the respirations are normal, abnormally fast (tachypnea), abnormally slow (technically termed bradypnea), or nonexistent (apnea).
    Rate, sed: A sedimentation rate, or "sed rate", is a blood test that detects and is used to monitor inflammation activity. It is measured by recording the rate at which red blood cells (RBCs) sediment in a tube over time. It increases (the RBCs sediment faster) with more inflammation.
    Rate, sedimentation: A sedimentation rate, or "sed rate", is a blood test that detects and is used to monitor inflammation activity. It is measured by recording the rate at which red blood cells (RBCs) sediment in a tube over time. It increases (the RBCs sediment faster) with more inflammation.
    Rattlesnake bite: A venomous (poisonous) snake bite. All rattlesnakes are venomous and secrete poisonous venom.
    Raynaud’s phenomenon: A condition resulting in discoloration of fingers and/or toes when a person is exposed to changes in temperature (cold or hot) or emotional events. Skin discoloration occurs because an abnormal spasm of the blood vessels causes a diminished blood supply. Initially, the digits involved turn white because of diminished blood supply, then turn blue because of prolonged lack of oxygen and finally, the blood vessels reopen, causing a local "flushing" phenomenon, which turns the digits red. This three-phase color sequence (white to blue to red), most often upon exposure to cold temperature, is characteristic of Raynaud’s phenomenon. Named for the French physician Maurice Raynaud (1834-1881).
    Reabsorption: Absorbing again. For example, the kidney selectively reabsorbs substances such as glucose, proteins, and sodium which it had already secreted into the renal tubules. These reabsorbed substances return to the blood.
    Reaction, allergic: A reaction that occurs when the immune system attacks a usually harmless substance (an allergen) that gains access to the body. The immune system calls upon a protective substance called immunoglobulin E (IgE) to fight these invading allergic substances ( allergens). Even though everyone has some IgE, an allergic person has an unusually large army of these IgE defenders -in fact, too many for their own good. This army of IgE antibodies attacks and engages the invading army of allergic substances of allergens. As is often the case in war, innocent bystanders are affected by this battle. These innocent bystanders are special cells called mast cells. These cells are frequently injured during the warring of the IgE antibodies and the allergic substances. When a mast cell is injured, it releases a variety of strong chemicals including histamine into the tissues and blood that frequently cause allergic reactions. These chemicals are very irritating and cause itching, swelling, and fluid leaking from cells. These allergic chemicals can cause muscle spasm and can lead to lung and throat tightening as is found in asthma and loss of voice.
    Reactive arthritis: Reiter’s syndrome is also called "reactive arthritis" since it is thought to involve the immune system which is "reacting" to the presence of bacterial infections in the genital, urinary, or gastrointestinal systems. Accordingly, certain people’s immune systems are genetically primed to react aberrantly when these areas are exposed to certain bacteria. The aberrant reaction of the immune system leads to inflammation in the joints and eyes.
    Reading frame: One of the three possible ways to read a nucleotide sequence in DNA (depending upon whether reading starts with the first, second or third base in a triplet).
    Reading frame, open: An open reading frame in DNA has no termination codon, no signal to stop reading the nucleotide sequence, and so may be translated into protein.
    Reagent: A substance used to produce a chemical reaction to detect, measure, produce, etc. other substances.
    Rebound: Just like a rebound in basketball when the ball reverses its course and bounces back off the backboard, in medicine a rebound is a reversal of response upon withdrawal of the stimulus.
    Rebound effect: The characteristic of a drug to produce reverse effects when the effect of the drug has passed or the patient no longer responds to it.
    Recalcitrant: Stubborn. For example, a recalcitrant case of pneumonia stubbornly resists treatment.
    Receptor: In cell biology, a receptor is a structure on the surface of a cell or inside a cell that selectively receives and binds a specific substance. There are, for example, insulin receptors, low-density lipoprotein (LDL) receptors, etc. However, in neurology, a receptor is the terminal of a sensory nerve that (receives and) responds to stimuli.

    Receptor, visual: The layer of rods and cones, the visual cells, of the retina.
    Recessive: A recessive gene expresses itself only when there is no other type of gene present at that locus (spot on the genetic code or chromosome). For example, cystic fibrosis (CF) and Duchenne muscular dystrophy (DMD) are both recessive disorders. A CF child has the CF gene on both chromosome 7’s (and so is said to be homozygous for CF). The DMD boy has the DMD gene on his sole X chromosome (and so is said to be hemizgous for DMD).
    Recessive, autosomal: A gene on a nonsex chromosome (an autosome) that expresses itself only when there is no different gene present at that locus (spot on the chromosome). For example, cystic fibrosis (CF) is an autosomal recessive disorder. A CF child has the CF gene on both chromosome 7’s (and so is said to be homozygous for CF).
    Recessive, X-linked: A gene on the X chromosome that expresses itself only when there is no different gene present at that locus (spot on the chromosome). For example, Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder. A DMD boy has the DMD gene on his sole X chromosome (and so is said to be hemizgous for DMD). Although it is much rarer, a girl can have DMD (by several different means as, for example, if she has the DMD gene on both her X chromosomes and so is homozygous for DMD).

    Recipient: In medicine, a recipient is someone who receives something like a blood transfusion or an organ transplant. The recipient is beholden to the donor.
    Reciprocal treanslocation: Mutual exchange of chromosome segments between two nonhomologous chromosomes (chromosomes that do not belong to the same pair).
    Recombinant: A person with a new combination of genes, a combination of genes not present in either parent, due to parental recombination of those genes.
    Recombinant clones: Clones containing recombinant DNA molecules.
    Recombinant DNA molecules: A combination of DNA molecules of different origin that are joined using recombinant DNA technology.
    Recombinant DNA technology: A series of procedures used to join together (recombine) DNA segments. A recombinant DNA molecule is constructed (recombined) from segments from 2 or more different DNA molecules. Under certain conditions, a recombinant DNA molecule can enter a cell and replicate there, autonomously (on its own) or after it has become integrated into a chromosome.
    Recombination: The trading of fragments of genetic material between chromosomes before the egg and sperm cells are created. Key features of recombination include the point-to-point association of paired chromosomes (synapsis) followed by the visible exchange of segments (crossing over) at X-shaped crosspoints (chiasmata). Recombination is the principal way of creating genetic diversity between generations. By shuffling the genetic deck of cards, recombination ensures that children are dealt a different genetic hand than their parents.
    RECOMBIVAX-HB: A vaccine against hepatitis B (hep B) to stimulate the body’s immune system to produce antibodies against the hep B virus.
    Recrudescence: Reappearance. In Latin, recrudescere meant to become raw or sore again. Recrudescence has broadened out so there can now be the recrudescence of a rash, of arthritis, etc.
    Rectal: Having to do with the rectum.
    Rectal cancer: A malignant tumor arising from the inner wall of the large intestine. The third leading cause of cancer in males, fourth in females in the U.S. Risk factors include heredity (family history), colon polyps, and long-standing ulcerative colitis. Most colorectal cancers develop from polyps. Colon polyp removal can prevent colorectal cancer. Colon polyps and early cancer can have no symptoms so regular screening is important. Diagnosis of colorectal cancer can be made by barium enema or by colonoscopy with biopsy confirmation of cancer.
    Rectum: The last 6 to 8 inches of the large intestine. The rectum stores solid waste until it leaves the body through the anus. The word rectum comes from the Latin rectus meaning straight (which the human rectum is not).
    Recuperate: To recover health and strength. From the Latin recuperare meaning to regain, get back, recover. To recuperate is to convalesce.
    Recur: To occur again. To return. Any symptom (such as fatigue), any sign (such as a heart murmur), or any disease can recur.
    Recurrence: The return of a sign, symptom or disease after a remission. The reappearance of cancer cells at the same site or in another location is, unfortunately, a familiar form of recurrence.

    Recurrence risk: In medical genetics, the recurrence risk is the chance that a genetic (inherited) disease present in the family will recur in that family and affect another person (or persons). It is the chance of "lightning striking twice" (or thrice, etc.).
    Recurrent: Back again. A recurrent fever is a fever that has returned after an intermission: a recrudescent fever.
    Recurrent laryngeal nerve: A branch of a nerve (the vagus nerve) that comes down the neck and turns back ("recurs") to supply the larynx (the "voice box").
    Red blood cells: Red blood cells (RBCs) are cells that carry oxygen in the blood. They are also called red corpuscles.
    Red cells: Short for red blood cells, the oxygen/carbon dioxide carrying cells in blood. Also known acronymically as RBC’s, red corpuscles or erythrocytes (literally, red hollow vessels).
    Red corpuscles: Red corpuscles are cells that carry oxygen in the blood. They are also called red blood cells or "RBCs."
    Reduction division: The first cell division in meiosis, the process by which germ cells are formed. A unique event in which the chromosome number is reduced from diploid (46 chromosomes) to haploid (23 chromosomes). Also called first meiotic division or first meiosis.
    Reed-Sternberg cell: A type of cell that appears in patients with Hodgkin's disease. The number of these cells increases as the disease advances.
    Referral: The recommedation of a medical or paramedical professional. If you get a referral, for example, to ophthalmology, you are sent to the eye doctor. The earliest recorded use of the word referral in medicine was in 1927.

    Reflex: A reaction that is involuntary. The corneal reflex is the blink that occurs with irritation of the eye. The nasal reflex is a sneeze.
    Reflex sympathetic dystrophy syndrome (RSDS): A condition that features a group of typical symptoms, including pain (often "burning" type), tenderness, and swelling of an extremity associated with varying degrees of sweating, warmth and/or coolness, flushing, discoloration, and shiny skin.
    Reflux: The term used when liquid backs up into the esophagus from the stomach.
    Reflux disease, gastroesophageal (GERD): The stomach contents regurgitate and back up (reflux) into the esophagus The food in the stomach is partially digested by stomach acid and enzymes. Normally, the partially digested acid content in the stomach is delivered by the stomach muscle down into the small intestine for further digestion. With esophageal reflux, stomach acid content refluxes back up into the esophagus, occasionally reaching the breathing passages, causing inflammation and damage to the esophagus, as well as to the lung and larynx (the voice box). 10% of patients with GERD develop Barrett’s esophagus, a risk fractor in cancer of the esophagus.
    Reflux, esophageal: A condition wherein stomach contents regurgitate or back up (reflux) into the esophagus (a long cylindrical tube that transports food from the mouth to the stomach). The food in the stomach is partially digested by stomach acid and enzymes. Normally, the partially digested acid content in the stomach is delivered by the stomach muscle into the small intestine for further digestion. In esophageal reflux, stomach acid content refluxes backwards up into the esophagus, occasionally reaching the breathing passages, causing inflammation and damage to the esophagus, as well as to the lung and larynx (the voice box). The overall process is medically termed gastroesophageal reflux disease (GERD). 10% of patients with GERD develop a Barrett’s esophagus which can increase the risk of cancer of the esophagus.
    Reflux laryngitis: Inflammation of the voice box (larynx) caused by stomach acid backing up into the esophagus. Reflux laryngitis can cause chronic hoarseness and be associated with other symptoms of inflammation of the esophagus, such as heartburn. Many treatment options are available.
    Refraction: Checking the eyes for refractive errors (nearsighted, farsighted, astigmatism) and correcting those errors.
    Refractory: Not yielding (at least not yielding readily) to treatment.
    Refractory anemia: Anemia (a shortage of red blood cells) unresponsive to treatment.
    Refsum’s disease: A genetic disorder of the fatty acid phytanic acid which accumulates and causes a number of progressive problems including polyneuritis (inflammation of numerous nerves), diminishing vision (due to retinitis pigmentosa), and wobbliness (ataxia) caused by damage to the cerebellar portion of the brain (cerebellar ataxia).
    Regenerate: To reproduce or renew something lost. For example, after an injury, the liver has the capacity to regenerate.

    Regimen: With the accent on the first syllable (reg as in Reggie Jackson), a regimen is a plan, a regulated course such as a diet, exercise or treatment, designed to give a good result. A low-salt diet is a regimen.
    Region, regulatory: See: Regulatory sequence.
    Regional eneteritis: Crohn’s disease, a chronic inflammatory disease of the intestine primarily in the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be chronic, recurrent with periods of remission and exacerbation. In the early stages, it causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs.When only the large intestine (colon) is involved, the condition is called Crohn’s colitis. When only the small intestine is involved, the condition is called Crohn’s enteritis. When only the end of the small intestine (the terminal ileum) is involved, it is termed terminal ileitis. When both the small intestine and the large intestine are involved, the condition is called Crohn’s enterocolitis (or ileocolitis). Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery. (The disease is also called granulomatous enteritis).
    Registry: Although a registry was originally the place (like Registry House in Edinburgh) where information was collected (in registers), the word registry has also come to mean the collection itself. A registry is usually organized so the data can be analyzed. For example, analysis of data in a tumor registry maintained at a hospital may show a rise in lung cancer among women.
    Regress: To return or go back. For example, if a 5-year-old child begins to regress (and function like a much younger child), that is worrisome.
    Regulatory gene: A gene that regulates the expression of other genes. A regulatory gene is a nosy gene whose prime preoccupation is to horn in on other genes and control the rate at which they make products.
    Regulatory region: See: Regulatory sequence.
    Regulatory sequence: A sequence of bases in DNA that controls gene expression.
    Regurgitation: A backward flowing. For example, of food. Or the sloshing of blood back into the heart (or between chambers of the heart) when a heart valve is incompetant and does not close effectively.
    Rehab: Short for Rehabilitation.

    Rehabilitation: The restoration of skills by a person who has suffered an illness or injury so they regain maximum self-sufficiency. After a stroke, rehabilitation may be important to walk again and speak clearly again.
    Rehydrate: To restore water. If a child has severe diarrhea, loses a lot of water in the stools and so becomes seriously dehydrated, it is imperative to rehydrate that child properly and promptly.
    Reiter’s syndrome: A chronic form of inflammatory arthritis wherein the following three conditions are combined: (1) arthritis; (2) inflammation of the eyes (conjunctivitis); and (3) inflammation of the genital, urinary or gastrointestinal systems.
    Rejection: In transplantation biology, the refusal by the body to accept transplanted cells, tissues or organs. For example, a kidney transplanted may be rejected.
    Relapse: The return of signs and symptoms of a disease after a remission.
    Relaxant: Something that relaxes, relieves, reduces tension. For example, a muscle relaxant is often administered during abdominal surgery to relax the diaphragm and keep it from moving during the surgery.
    rem: In radiation, Roentgen equivalent for man, a roentgen (an international unit of X- or gamma-radiation) adjusted for the atomic makeup of the human body. In ophthalomology, rapid eye movement.
    Remedy: Something that consistently helps treat or cures a disease. From the Latin remedium meaning that which heals again (and again).
    Remission: Disappearance of the signs and symptoms of cancer or other disease. When this happens, the disease is said to be "in remission." A remission can be temporary or permanent.
    Remission induction chemotherapy: The initial chemotherapy a patient with acute leukemia receives to bring about a remission.
    Renal: Having to do with the kidney. From the Latin renes (the kidneys), which gave the French les reins which mean both the kidneys and the lower back.
    Renal cancer: Childhood kidney cancer is different from adult kidney cancer. The most common symptom of kidney cancer is blood in the urine. The diagnosis of kidney cancer is supported by findings of the medical history and examination, blood, urine, and x-ray tests, and confirmed by a biopsy.
    Renal capsule: The fibrous connective tissue that surrounds each kidney.
    Renal cell cancer: Cancer that develops in the lining of the renal tubules, which filter the blood and produce urine. Also called renal cell carcinoma.
    Renal cell carcinoma: Cancer that develops in the lining of the renal tubules, which filter the blood and produce the urine. Also called renal cell cancer.
    Renal osteodystrophy: A combination of bone disorders usually caused by chronic kidney failure (renal disease). Can also occur because of abnormal kidney functioning at birth (congenital). When the kidneys have failed, death is imminent unless dialysis is given. Therefore, patients with osteodystrophy are usually on dialysis therapy. This bone disease, which is also simply called osteodystrophy, is common in patients on chronic hemodialysis.
    Renal pelvis: The area at the center of the kidney. Urine collects here and is funneled into the ureter.
    Renal tubules: Small structures in the kidney that filter the blood and produce the urine.
    rep: Stands for roentgen equivalent physical. A rep is a unit of absorbed radiation approximately equivalent to a roentgen, an international unit of X- or gamma-radiation.
    Repair, DNA: The cell has a series of special enzymes to repair mutations (changes) in the DNA and restore the DNA to its original state.
    Reperfusion: The restoration of blood flow to an organ or tissue. After a heart attack, an immediate goal is to quickly open blocked arteries and reperfuse the heart muscles. Early reperfusion minimizes the extent of heart muscle damage and preserves the pumping function of the heart.
    Repetitive DNA: DNA sequences that are repeated in the genome.
    Replication: A turning back, repetition, duplication, reproduction.
    Replication, DNA: A wondrous complex process whereby the ("parent") strands of DNA in the double helix are separated and each one is copied to produce a new ("daughter") strand. This process is said to be "semi-conservative" since one of each parent strand is conserrved and remains intact after replication has taken place.
    Reporting, anonymous: In public health, anonymous reporting permits the acquisition of certain data such as the proportion of persons with a positive test or with a disease. It is different from anonymous testing, in which no name is used on the test sample.
    Reporting, named: In public health, named reporting is the reporting of infected persons by name to public health departments. This is standard practice for the surveillance of many infectious diseases such as syphilis, gonorrhea, and tuberculosis that pose a public health threat. The opposite of named reporting is anonymous testing in which the individual remains nameless.
    Reporting, unique identifier: In public health, a system that uses information such as the person’s birth date and part of their identification number (in the U.S., the social security number) to create a unique code that is reported instead of a name. It is an alternative to named reporting that provides some of the surveillance benefits of reporting by name, such as the elimination of duplicate reports, while reducing privacy concerns by avoiding use of a person’s name. This system is used with HIV testing for example in Maryland and Texas.
    Reproduction: The production of offspring. Reproduction need not be sexual. Yeast can reproduce by budding.
    Reproductive cells: The eggs and sperm are the reproductive cells. Each mature reproductive cell is haploid in that it has a single set of 23 chromosomes.
    Reproductive system: In women, the organs that are directly involved in producing eggs and in conceiving and carrying babies.
    Resection: Surgical removal of part of an organ.
    Reservoir, Ommaya: A device implanted under the scalp and used to deliver anticancer drugs to the fluid surrounding the brain and spinal cord.
    Residual: Something left behind. With residual disease, the disease has not been eradicated.
    Resistance, antibiotic: The ability of bacteria and other microorganisms to withstand an antibiotic to which they were once sensitive (and were once stalled or killed outright). Also called drug resistance.
    Resistance, pulmonary: The opposition of the respiratory tree to air flow.
    Resistance, vascular: The opposition to the flow of blood across a vascular bed.
    Resolution: In genetics, resolution refers to the degree of molecular detail on a physical map of DNA, ranging from low to high.
    Resorb: Literally, to absorb again. To lose substance. Some of a tooth may be resorbed.
    Resorption: The process of losing substance. Bone when it is remodeled (reshaped) undergoes both new formation and resorption.
    Respiration: Respiration is the act of inhaling and exhaling air in order to exchange oxygen for carbon dioxide.
    Respiratory: Having to do with respiration. The word comes from the Latin re- (again) + spirare (to breathe) = to breathe again.
    Respiratory rate: The number of breaths per minute (or, more formally, the number of movements indicative of inspiration and expiration per unit time). In practice, the respiratory rate is usually determined by counting the number of times the chest rises (or falls) per minute. By whatever means, the aim is to determine if the respirations are normal, abnormally fast (tachypnea), abnormally slow (technically termed bradypnea), or nonexistent (apnea).
    Respiratory system: The organs that are involved in breathing. These include the nose, throat, larynx, trachea, bronchi, and lungs.
    Respiratory therapy: Exercises and treatments that help patients recover lung function, such as after surgery.
    Resting phase: More appropriately called interphase. The interval in the cell cycle between two cell divisions when the individual chromosomes cannot be distinguished, interphase was once thought to be the resting phase but it is far from a time of rest for the cell. It is the time when DNA is replicated in the cell nucleus.
    Restitution: In cytogenetics, the spontaneous rejoining of broken chromosomes to reconstitute the original chromosome configuration.
    Restriction endonuclease: An enzyme from bacteria that can recognize specific base sequences in DNA and cut (restrict) the DNA at that site (the restriction site). Also called a restriction enzyme.
    Restriction enzyme: An enzyme from bacteria that can recognize specific base sequences in DNA and cut (restrict) the DNA at that site (the restriction site). Also called a restriction endonuclease.
    Restriction fragment length polymorphism (RFLP): A difference in DNA between people that can be recognized by the use of a restriction enzyme.
    Restriction map: An array of sites in DNA susceptible to cleavage by diverse restriction enzymes.
    Restriction site: A sequence in DNA that can be recognized and cut by a specific restriction enzyme.
    Retinoblastoma: A malignant eye tumor caused by the loss of a pair of tumor-suppressor genes. An inherited form of retinoblastoma (it typically appears at birth, leads to multiple tumors and affects both eyes) is due to a transmissible (germline) mutation followed by an acquired (somatic) mutation. The sporadic form of retinoblastoma (it has later onset and leads to a single tumor in one eye) is due to acquired (somatic) mutations of both tumor-suppressor genes. When the tumor is detected at an early stage, it can sometimes be treated locally, but it oftren unfortunately requires removal of the eye (enucleation).
    Retropubic prostatectomy: Surgical removal of the prostate through an incision in the abdomen.
    Retrosternal: Behind the sternum (the breastbone).
    Retrovirus: An RNA virus (a virus composed not of DNA but of RNA). Retroviruses have an enzyme called reverse transcriptase that gives them the unique property of transcribing RNA (their RNA) into DNA. The retroviral DNA can then integrate into the chromosomal DNA of the host cell to be expressed there.
    Reversal of organs, total: This condition (medically called situs inversus totalis) involves complete transposition (right to left reversal) of the thoracic and abdominal organs. The heart is not in its usual position in the left chest but is on the right. Specifically related to the heart, this is referred to as dextrocardia (literally, right-hearted). And the stomach, which is normally in the left upper abdomen, is on the right. In patients with situs inversus totalis, all of the chest and abdominal organs are reversed and appear in mirror image when examined or visualized by tests such as x-ray filming. Situs inversus totalis has been estimated to occur once in about 6-8,000 births. Situs inversus occurs in a rare abnormal condition that is present at birth (congenital) called Kartagener’s syndrome.
    Reverse genetics: In classic genetics, the traditional approach was to find a gene product and then try to identify the gene itself. In molecular genetics, the reverse has been done by identifying genes purely on the basis of their position in the genome with no knowledge whatsoever of the gene product. This revolutionary approach is reverse genetics. Also called positional cloning.
    Reverse transcriptase: An enzyme that permits DNA to be made using RNA as the template. A retrovirus (a virus composed of RNA) can propagate by converting its RNA into DNA with the invaluable assistance of reverse transcriptase.
    Reye’s syndrome: A sudden, sometimes fatal, disease of the brain (encephalopathy) with degeneration of the liver, occurs in children (most cases 4-12 years of age), comes after the chickenpox (varicella) or an influenza-type illness, is also associated with taking medications containing aspirin. The child with Reye’s syndrome first tends to be unusually quiet, lethargic (stuporous), sleepy, and vomiting. In the second stage, the lethargy deepens, the child is confused, combative and delirious. And things get worse from there with decreasing consciousness, coma, seizures, and eventually death. The prognosis (outlook) depends on early diagnosis and control of the increased intracranial pressure. Reye’s syndrome is a good reason to have your child immunized against chickenpox and not give the child aspirin for fever.
    RF: Rheumatoid factor.
    RFLP (Restriction Fragment Length Polymorphism ): A difference in DNA between people that can be recognized by the use of a restriction enzyme.
    Rh: A blood group system and one of the most complex. A person can be said to be Rh-positive or Rh-negative. Rh stands for rhesus monkeys.
    Rhabdomyolysis: A condition whereby skeletal muscle is broken down, releasing intracellular (inside the cell) muscle enzymes and electrolytes. The major risks of this condition are two fold: one is obviously muscle breakdown and the other is kidney failure. The myoglobin, an intracellular component, is toxic to the kidneys and may lead to kidney failure. Rhabdomyolysis is relatively uncommon, but most often occurs as the result of extensive muscle damage, for example crush injury or electrical shock. Other causes many be drug or toxin, for example many of the cholesterol lowering medications have the potential to cause this disorder. Underlying diseases can also lead to rhabdomyolysis, including collagen vascular diseases (such as systemic lupus erythematosus) and others, which if left untreated may also cause this muscle degradation.
    Rheumatism: Rheumatism is an older term, used to describe any of a number of painful conditions of muscles, tendons, joints, and bones.
    Rheumatoid arthritis: An autoimmune disease which causes chronic inflammation of the joints, the tissue around the joints, as well as other organs in the body. Autoimmune diseases occur when the body tissues are mistakenly attacked by its own immune system. The immune system is a complex organization of cells and antibodies designed normally to "seek and destroy" invaders of the body, particularly infections. Patients with these diseases have antibodies in their blood which target their own body tissues, where they can be associated with inflammation. Because it can affect multiple other organs of the body, rheumatoid arthritis is referred to as a systemic illness and is sometimes called rheumatoid disease. While rheumatoid arthritis is a chronic illness (meaning it can last for years) patients may experience long periods without symptoms.
    Rheumatoid arthritis, systemic-onset juvenile (Still’s disease): Also known as systemic-onset juvenile chronic arthritis. Still’s disease presents with systemic (bodywide) illness including high intermittent fever, a salmon-colored skin rash, swollen lymph glands, enlargement of the liver and spleen, and inflammation of the lungs (pleuritis) and around the heart (pericarditis). The arthritis may not be immediately apparent but it does appear and may persist after the systemic symptoms are gone.
    Rheumatoid factor: Rheumatoid factor is an antibody that is measurable in the blood. It is commonly used as a blood test for the diagnosis of rheumatoid arthritis. Rheumatoid factor is present in about 80% of adults (but a much lower proportion of children) with rheumatoid arthritis. It is also present in patients with other connective tissue diseases (such as systemic lupus erythematosus) and in some with infectious diseases (such as infectious hepatitis).
    Rheumatoid nodules: Rheumatoid nodules are firm lumps in the skin of patients with rheumatoid arthritis that usually occur in pressure points of the body, most commonly the elbows
    Rheumatology: A subspecialty of internal medicine that involves the non-surgical evaluation and treatment of the rheumatic diseases and conditions. Rheumatic diseases and conditions are characterized by symptoms involving the musculoskeletal system. Many of the rheumatic diseases and conditions feature immune system abnormalities. Therefore, rheumatology also involves the study of the immune system. Classical rheumatology training includes 4 years of medical school, 1 year of internship in internal medicine, 2 years of internal medicine residency, and 2 years of rheumatology fellowship. There is a subspecialty board for rheumatology certification. The American College of Rheumatology is the official organization acting on behalf of the field of rheumatology in the United States.
    Rhinitis: Irritation of the nose. Derived from the Greek word rhinos meaning of the nose.
    Rhinitis, allergic: The medical term for hayfever. (Hay fever"is a misnomer since hay is not a usual cause of this problem and there is no fever. Many substances cause the allergic symptoms in hay fever. Allergic rhinitis is the correct term for this allergic reaction. Rhinitis means "irritation of the nose" and is a derivative of Rhino, meaning nose.) Symptoms include nasal congestion, a clear runny nose, sneezing, nose and eye itching, and tearing eyes. Post-nasal dripping of clear mucus frequently causes a cough. Loss of smell is common and loss of taste occurs occasionally. Nose bleeding may occur if the condition is severe. Eye itching, redness, and tearing frequently accompany the nasal symptoms.
    Rhinitis, allergic, perennial: Allergic rhinitis (hayfever) that occurs throughout the year.
    Rhinitis, allergic, seasonal: Allergic rhinitis (hayfever) which occurs during a specific season.
    Rhinoplasty: Plastic surgery on the nose, known familiarly as a nose job.
    Rhinorrhea: Medical term for a runny nose. From the Greek words "rhinos" meaning "of the nose" and "rhoia" meaning "a flowing."
    Rib: Any one of the twelve paired bones which form the skeletal structure of the chest wall (rib cage). The ribs attach to the building blocks of the spine (vertebrae) in the back. The first seven ribs attach to the sternum in the front and are known as true ribs. The lower five ribs do not directly connect to the sternum and are known as false ribs.
    RiboNucleic Acid (RNA): A chemical similar to DNA, The several classes of RNA molecules play important roles in protein synthesis and other cell activities.
    Ribosomes: Structures (called organelles) composed of RNA and protein situated outside the nucleus in the cytoplasm of the cell where the cell uses messenger RNA to make up polypeptides.
    Rickettsia: A member of a group of microorganisms that (like viruses) require other living cells for growth but (like bacteria) use oxygen, have metabolic enzymes and cell walls, and are susceptible to antibiotics. Rickettsiae cause a series of diseases (See Rickettsial diseases).
    Rickettsial diseases: The infectious diseases caused by the rickettsiae fall into 4 groups:(1) typhus: epidemic typhus, Brill-Zinsser disease, murine (endemic) typhus, and scrub typhus; (2) spotted fever—Rocky Mountain spotted fever, Eastern tick-borne rickettsioses, and rickettsialpox; (3) Q fever; and (4) trench fever.
    Rickettsialpox: A mild infectious disease first observed in New York City caused by Rickettsia akari, transmitted from its mouse host by chigger or adult mite bites. There is fever, a dark spot that becomes a small ulcer at the site of the bite, swollen glands (lymphadenopathy) in that region, and a raised blistery (vesicular) rash. Also known as vesicular rickettsiosis.
    Rickettsioses: The infectious diseases caused by the rickettsiae. See Rickettsial diseases.
    Rickettsioses of the eastern hemisphere, tick-borne: Thare are 3 known diseases caused by infection with rickettsial agents> They are North Asian tick-borne rickettsiosis, Queensland tick typhus, and African tick typhus (fièvre boutonneuse).
    Rickettiosis, North Asian tick-borne: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.
    Rickettsiosis, vesicular: See Rickettsialpox.
    Ring chromosome: A structurally abnormal chromosome in which the end of each chromosome arm has been lost and the broken arms have been reunited in ring formation. A ring chromosome is denoted by the symbol r.
    Ringworm of the nails: The most common fungus infection of the nails (onychomycosis). Onychomycosis makes the nails look white and opaque, thickened, and brittle. Older women (perhaps because estrogen deficiency may increase the risk of infection). and men and women with diabetes or disease of the small blood vessels (peripheral vacscular disease) are at increased risk. Artificial nails (acrylic or "wraps") increase the risk because when an artificial nail is applied, the nail surface is usually abraded with an emery board damaging it, emery boards can carry infection, and. water can collect under the nail creating a moist, warm environment for fungal growth. Alternative names include tinea unguium and dermatophytic onychomycosis.
    Risk factor: Something that increases a person's chances of developing a disease.
    Risk of recurrence: In medical genetics, the chance that a genetic (inherited) disease present in a family will recur in that family. The concept in general medicine means the chance that an illness we come back again.
    Ritter disease: This is the scalded skin syndrome, a potentially serious side effect of infection with the Staph (Staphylococcus) bacteria that produces a specific protein which loosens the "cement" holding the various layers of the skin together. This allows blister formation and sloughing of the top layer of skin. If it occurs over large body regions it can be deadly (just like a large surface area of the body having been burned). It is necessary to treat scalded skin syndrome with intravenous antibiotics and to protect the skin from allowing dehydration to occur if large areas peel off. The disease occurs predominantly in children under 5 years of age. It is known formally as Staphyloccoccal scalded skin syndrome.
    RMSF: Rocky Mountain spotted fever.
    RNA: Short for ribonucleic acid. A chemical (specifically, a nucleic acid) similar to DNA but containing ribose rather than deoxyribose. RNA is in fact formed upon a DNA template. The several classes of RNA molecules play crucial roles in protein synthesis and other cell activities. (See also messenger RNA, transfer RNA and ribosomal RNA.)
    RNA, messenger: A class of RNA that is the template upon which polypeptides are put together. Abbreviated mRNA.
    RNA polymerase: Enzyme that catalyzes (speeds) the polymerization of RNA. RNA polymerase uses preexisting nucleic acid templates and assembles the RNA from ribonucleotides.
    RNA, ribosomal: A component of ribosomes, ribosomal RNA functions as a nonspecific site for making polypeptides. Ribosomal RNA is abbreviated rRNA.
    RNA, transfer: In cooperation with the ribosomes, transfer RNA brings (transfers) activated amino acids into position along the messenger RNA template. The abbreviation for transfer RNA is tRNA.
    RNA polymerase: A polymerase is an enzyme that catalyzes the joining of many smaller molecules (called monomers) to form a big molecule (a macromolecule). RNA polymerase is a unique enzyme that makes (synthesizes) thye macromolecule RNA using DNA as the template.
    Robertsonian translocation: A type of chromosome rearrangement involving all of the essential genetic material of the long arms of two acrocentric chromosomes. The acrocentric chromosomes (those with the centromere near the end so there is only a tiny short arm) are chromosomes 13-15, 21 and 22 in humans. Named after W.R.B. Robertson who in 1916 first described this kind of chromosome rearrangement (in grasshoppers), Robertsonian translocations are also known as whole-arm or centric-fusion translocations. They are relatively common in humans and contribute to the toll of trisomy 13 syndrome and Down syndrome.
    Rocky Mountain spotted fever (RMSF): An acute febrile (feverish) disease initially recognized in the Rocky Mountain states, caused by Rickettsia rickettsii transmitted by hard-shelled (ixodid) ticks. Occurs only in the Western Hemisphere. Anyone frequenting tick-infested areas is at risk for RMSF. Onset of symptoms is abrupt with headache, high fever, chills, muscle pain. and then a rash .The rickettsiae grow within damaged cells lining blood vessels which may become blocked by clots. Blood vessel inflammation (vasculitis) is widespread Early recognition of RMSF and prompt antibiotic treatment is important in reducing mortality. Also called spotted fever, tick fever, and tick typhus.
    Roentgen: Named for Wilhelm Conrad Roentgen who discovered X-rays, a roentgen (abbreviated R). An international unit of X- or gamma-radiation.
    Roentgenology: Radiology is also known as roentgenology after Wilhelm Conrad Roentgen who discovered X-rays in 1895. Both terms refer to the science of radiation, both ionizing (like X-ray) and nonionizing (like ultrasound), applied to the diagnosis and treatment of disease.
    Rooting reflex: When the cheek or lip is touched, a newborn baby automatically roots and turns the face toward the stimulus. The rooting reflex helps with breast-feeding.
    Roseola: Short for Roseola infantum, a viral disease of infants and young children with sudden onset of high fever which lasts several days and then suddenly subsides leaving in its wake a fine red rash. The causative agent is herpesvirus type 6 so the disease is known as Sixth Disease. Also as Exanthem subitum (sudden rash), pseudorubella, roseola infantilis.
    Roseola infantilis: Another name for Roseola.
    Roseola infantum: The full name for Roseola.
    Rotavirus: A leading cause of severe diarrhea in early childhood (acute infantile gastroenteritis), rotavirus infection each year causes an estimated 500,000 doctor visits and 50,000 hospital admissions in the United States. Almost everyone catches rotavirus in childhood but, with good nutrition and rehydration, nearly all recover uneventfully. However, in poor countries there are at least 600,000 deaths of children under 5 years from rotavirus diarrhea and dehydration. Rotavirus was discovered in 1973 and took its name from its wheel-like appearance (rota means wheel in Latin). A vaccine has been reported in The New England Journal of Medicine (vol. 337, pp. 1181-7, 1997) to provide a high level of protection against severe diarrhea caused by rotavirus.
    Rothmund-Thomson syndrome (RTS): A genetic disorder with numerous features affecting skin (premature aging, excess pigmentation, dilated blood vessels),eyes (juvenile cataract), nose (saddle nose), teeth (maldeveloped), skeletal system (congenital bone defects) hair (abnormal), gonads (underdevelopment) limbs (soft tissue contractures), growth (short stature), blood (anemia) and a tendency to develop a type of bone cancer (osteogenic sarcoma). The RTS gene is on chromosome 8. The syndrome is recessive so to be affected with RTS a child has to have two RTS genes, one from each parent. RTS is also called "poikiloderma atrophicans and cataract".
    Rubella immunization: The standard MMR vaccine is given to prevent measles, mumps and rubella (German measles). The MMR vaccine is now given in two dosages. The first should be given at12-15 months of age. The second vaccination should be given at 4-6 years (or, alternatively, 11-12 years) of age. Most colleges require proof of a second measles or MMR vaccination prior to entrance. Most children should receive MMR vaccinations. Exceptions may include children born with an inability to fight off infection, some children with cancer, on treatment with radiation or drugs for cancer, on long term steroids (cortisone). People with severe allergic reactions to eggs or the drug neomycin should probably avoid the MMR vaccine. Pregnant women should wait until after delivery before being immunized with MMR. People with HIV or AIDS should normally receive MMR vaccine. Measles, mumps, and rubella vaccines may be administered as individual shots, if necessary, or as a measles-rubella combination.
    Runny nose: Rhinorrhea is the medical term for this common problem. From the Greek words "rhinos" meaning "of the nose" and "rhoia" meaning "a flowing."

    Ruptured spleen: Rupture of the capsule of the spleen, an organ in the upper left part of the abdomen, is a potential catastrophe that requires immediate medical and surgical attention. Splenic rupture permits large amounts of blood to leak into the abdominal cavity which is severely painful.and life-threatening. Shock and, ultimately, death can result. Patients typically require an urgent operation. Rupture of a normal spleen can be caused by trauma, for example, in an accident. If an individual’s spleen is enlarged, as is frequent in mononucleosis, most physicians will not allow activities (such as major contact sports) where injury to the abdomen could be catastrophic.
  • SA node: Sinoatrial node. The pacemaker of the heart, located in the right atrium (upper chamber of the heart). The electrical signals initiated in the SA node are transmitted throuhg the atria and the ventricles to stimulate heart muscle contractions (heartbeats).
    Sabin vaccine: Oral Polio virus Vaccine (OPV). The polio virus in OPV is attenuated (weakened). The Sabin vaccine is named after the American virologist Albert Sabin. See Immunization, polio.
    Sagittal: A vertical plane passing through the body which divides it into left and right sides.
    Salivary: Glands in the mouth that produce saliva. The salivary glands can become inflamed in diseases, such as Sjogren's syndrome and mumps.
    Salk vaccine: Inactivated Polio Vaccine (IPV). The polio virus in IPV has been inactivated (killed). The Salk vaccine is named after the American physician-virologist Jonas Salk. See Immunization, polio.
    Salpingo-oophorectomy: Removal of the fallopian tubes and ovaries.
    Sapphism: Female homosexuality. Named after the poet Sappho who lived on the Greek island of Lesbos (circa 600 BC). She was a lesbian by geography and sexual orientation. Also called lesbianism.
    Sarcoma: A type of cancer that starts in bone or connective tissue.
    Satellite DNA: DNA that contains many tandem (not inverted) repeats of a short basic repeating unit. Satellite DNA is located at very specific spots in the genome (on chromosomes 1, 9, 16 and the Y chromosome, the tiny short arms of chromosomes 13-15 and 21 and 22, and near the centromeres of chromosomes).
    Scalded skin syndrome: A potentially serious side effect of infection with the Staph (Staphylococcus) bacteria that produces a specific protein which loosens the "cement" holding the various layers of the skin together. This allows blister formation and sloughing of the top layer of skin. If it occurs over large body regions it can be deadly (just like a large surface area of the body having been burned). It is necessary to treat scalded skin syndrome with intravenous antibiotics and to protect the skin from allowing dehydration to occur if large areas peel off. The disease occurs predominantly in children under 5 years of age. It is known formally as Staphyloccoccal scalded skin syndrome and as Ritter disease.
    Schistosoma haematobium: A species of trematode worm that parasitizes humans and causes urinary tract disease. See Schistosomiasis.
    Schistosoma japonicum: A species of trematode worm that parasitizes humans and that (like S. mansoni) causes liver and gastrointestinal tract disease. See Schistosomiasis.
    Schistosoma mansoni: A species of trematode worm that parasitizes humans and that (like S. japonicum) causes liver and gastrointestinal tract disease. See Schistosomiasis.
    Schistosomiasis: Disease of liver, gastrointestinal tract and bladder caused by trematode worms that parasitize people. The infection is acquired from infested water. Three main species of these trematode worms (flukes)--Schistosoma haematobium, S. japonicum, and S. mansoni—cause disease in humans. Larval forms of the parasite live in freshwater snails. The cercaria (form of the parasite) is liberated from the snail burrow into skin, transforms to the schistosomulum stage, and migrates to the urinary tract (S. haematobium), liver or intestine (S. japonicum, S.mansoni) where the adult worms develop. Eggs are shed into the urinary tract or the intestine and hatch to form miracidia (yet another form of the parasite) which then infect snails, completing the life cycle of the parasite. Adult schistosome worms can seriously damage tissue. Schistosome species which cannot live in man cause swimmer’s itch. Schistosomiasis is also called bilharzia after the shortlived German physician Theodor Bilharz (1825-1862)
    Schizophrenia: The most common form of psychosis, characterized by partial or total withdrawal of interest in the world outside of oneself and loss of intellectual and emotional function.
    Sciatica: Pain resulting from irritation of the sciatic nerve, typically felt at the back of the thigh. The sciatic nerve is the largest nerve in the body and begins from nerve roots in the lumbar spinal cord in the low back and extends through the buttock area to send nerve endings down the lower limbs. While sciatica is most commonly a result of a disc herniation directly pressing on the nerve, any cause of irritation or inflammation of this nerve can reproduce the symptoms of sciatica.
    Sclerencephaly: A general term for scarring and shrinkage of the substance of the brain. Sclerencephaly occurs because of chronic inflammation of the brain matter.
    Sclerosis, multiple (MS): The National Multiple Sclerosis Society says of MS that it is "a disease that randomly attacks your central nervous system, wearing away the control you have over your body. Symptoms may range from numbness to paralysis and blindness. The progress, severity and specific symptoms cannot be foreseen. You never know when attacks will occur, how long they will last, or how severe they will be. Most people are diagnosed with MS between the ages of 20 and 40...." In medical terms, MS involves demyelinization of the white matter sometimes extending into the gray matter. Demyelinization is loss of myelin, the coating of nerve fibers composed of lipids (fats) and protein that serves as insulation and permits efficient nerve fiber conduction. The "white matter" is the part of the brain which contains myelinated nerve fibers and appears white, whereas the gray matter is the cortex of the brain which contains nerve cell bodies and appears gray. When myelin is damaged in MS, nerve fiber conduction is faulty or absent. Impaired bodily functions or altered sensations associated with those demyelinated nerve fibers give rise to the symptoms of MS. Recent research (1998) has also identified nerve cell death as part of the nervous system injury in MS.
    Scoliosis: Sideways (lateral) curvature of the spine. Scoliosis is usually an incidental and harmless finding. When severe, scoliosis can be improved by surgical correction.
    Score, Apgar: A practical method to assess a newborn infant, the Apgar score is a number arrived at by scoring the heart rate, respiratory effort, muscle tone, skin color, and response to a catheter in the nostril. Each of these objective signs can receive 0, 1, or 2 points. An Apgar score of 10 means an infant is in the best possible condition.. The Apgar score is done routinely 60 seconds after the complete birth of the infant. An infant with a score of 0-3 needs immediate resusitation. The Apgar score is commonly repeated 5 minutes after birth and in the event of a difficult resusitation, the Apgar may be done again at 10, 15, and 20 minutes. An Apgar score of 0-3 at 20 minutes of age is predictive of high morbidity (disease) and mortality. The score is named for the American anesthesiologist Virginia Apgar (1909-1974) at Columbia University in New York who originated the scoring method.
    Scrape: Abrasion. Washing a cut or scrape with soap and water and keeping it clean and dry is all that is required to care for most wounds. Putting alcohol, hydrogen peroxide, and iodine into a wound can delay healing and should be avoided. Seek medical care early if you think that you might need stitches. Any delay can increase the rate of wound infection. Any puncture wound through tennis shoes has a high risk of infection and should be seen by your healthcare professional. Any redness, swelling, increased pain, or pus draining from the wound may indicate an infection that requires professional care.
    Scrotum: A pouch of skin which contains the testes, epididymides, and lower portions of the spermatic cords.
    Scrub typhus: A mite-borne infectious disease caused by a microorganism, Rickettsia tsutsugamushi, characteristically with fever, headache, a raised (macular) rash, swollen glands (lymphadenopathy) and a dark crusted ulcer (called an eschar or tache noire) at the site of the chigger (mite larva) bite. This disease occurs in the area bounded by Japan, India, and Australia. Known also as Tsutsugamushi disease, mite-borne typhus, and tropical typhus.
    Sebaceous cyst: A sebaceous cyst is a rounded swollen area of the skin formed by an abnormal sac of retained excretion (sebum) from the sebaceous follicles.
    Sebaceous gland: A normal gland of the skin which empties an oily secretion into the hair follicle near the surface of the skin.
    Seborrhea: A accumulation of scales of greasy skin, often on the scalp. Dandruff.
    Seborrheic keratosis: A benign skin lesion resulting from excessive growth of the top layer of skin cells. It usually is found in persons over 30 years old and may be few or numerous.
    Sebum: An oily secretion of the sebaceous gland which helps to preserve the flexibility of the hair.
    Secretin: Hormone made by glands in the small intestine that stimulates pancreatic secretion. The word "hormone" was coined by the English physiologists Wm. M. Bayliss and Ernest H. Starling in connection with their discovery of secretin, the first hormone, in 1902.
    Section (anatomic): A slice of tissue. A biopsy obtained by surgery is usually sectionned (sliced). And all the "sections" under the microscope might, for example, reveal entirely benign cells with no hint of cancer.
    Section (obstetrical): Short for a Caesarian section. In surgery, the word "section" refers to the division of tissue. Here, the division of tissue involves the abdominal wall of the mother and the wall of the uterus which are "sectionned" in order to deliver the baby from the uterus (womb).
    Section, Caesarian: Procedure in which an infant, rather than being born vaginally, is surgically removed from the uterus. As the name "Caesarian" suggests, this is not a new procedure. it was done in ancient civilizations upon the death of a pregnant woman near term to salvage the baby. Julius Caesar (or, more likely, one of his predecessors) was born by this procedure. The term "section" in surgery refers to the division of tissue. What is being divided here is the abdominal wall of the mother and the wall of the uterus in order to extract the baby. In Shakespeare’s "Macbeth" the Witches’ prophecy was that "...none of woman born/ Shall harm Macbeth" (IV.i). Unfortunately for Macbeth, the Scottish nobleman Macduff was "from his mother’s womb/ Untimely ripped." and thus not naturally "born of woman"(V.vii). Macduff is the only agent capable of destroying Macbeth. He kills Macbeth in battle.
    Section, cross: A transverse cut through a structure. The opposite is a longitudinal section.
    Section, longitudinal: A cut along the long axis of a structure
    Sedimentation rate: A sedimentation rate, or "sed rate", is a blood test that detects and monitors inflammation activity. It is measured by recording the rate at which red blood cells (RBCs) sediment in a tube over time. It increases (the RBCs sediment faster) with more inflammation.
    Segawa’s dystonia: An important variant of dopa-responsive dystonia (DRD). Typically, DRD begins in childhood or adolescence with progressive difficulty in walking and, in some cases, spasticity. In Segawa’s dystonia, the symptoms fluctuate during the day from relative mobility in the morning to increasingly worse disability in the afternoon and evening as well as after exercise.

    Seizure: A seizure is a sudden attack of epileptic convulsion. It is a result of involuntary electrical activity in the brain. It can be associated with uncontrolled motor (movement) or sensory system action. Accordingly, a patient suffering a seizure may experience uncontrollable body movements, unusual smells or tastes and have loss of consciousness (awareness of surroundings).
    Seizure, causes of: Known causes of seizures include head injuries, brain tumors, lead poisoning, maldevelopment of the brain, genetic and infectious illnesses. But in fully half of the patients with seizures, no cause can be found.
    Selective Estrogen-Receptor Modulator (SERM): A "designer estrogen" which possesses some, but not all, of the actions of estrogen. For example, raloxifene (trade name EVISTA) is classified as a SERM because it prevents bone loss (like estrogen) and lowers serum cholesterol (like estrogen) but (unlike estrogen) does not stimulate the endometrial lining of the uterus.
    Selenium: An essential mineral that is a component of a key antioxidant enzyme, glutathione reductase, in tissue respiration. Deficiency of selenium causes Keshan disease, a fatal form of cardiomyopathy (disease of the heart muscle) first observed in Keshan province in China and since found elsewhere. According to the National Academy of Sciences, the Recommended Dietary Allowances of selenium are 70 milligrams per day for men and 55 milligrams per day for women. Food sources of selenium include seafoods, some meats such as kidney and liver, and some grains and seeds. Too much selenium may cause reversible changes in the hair (balding) and nails, garlic odor to the breath, intestinal distress, weakness and slower mentation (slowed mental functioning).
    Selenium deficiency: Deficiency of the essential mineral selenium causes Keshan disease, a fatal form of cardiomyopathy (disease of the heart muscle) first observed in Keshan province in China and since found elsewhere. According to the National Academy of Sciences, the Recommended Dietary Allowances of selenium are 70 milligrams per day for men and 55 milligrams per day for women. Food sources of selenium include seafoods, some meats such as kidney and liver, and some grains and seeds
    Selenium excess: Too much of the mineral selenium may cause reversible changes in the hair (balding) and nails, garlic odor to the breath, intestinal distress, weakness and slower mentation (slowed mental functionning). According to the National Academy of Sciences, the Recommended Dietary Allowances of selenium are 70 milligrams per day for men and 55 milligrams per day for women.
    Seminal vesicles: Two structures about 5 cm long behind the bladder and above the prostate gland which contribute fluid to the ejaculate.
    Septal defect, atrial (ASD): A hole in the septum, the wall, between the atria, the upper chambers of the heart. Commonly called an ASD. ASDs are a major class of heart deformity that is present at birth (congenital cardiac malformation).
    Septal defect, ventricular (VSD): A hole in the interventricular septum, the wall between the ventricles, the lower chambers of the heart. Commonly called a VSD. VSDs are a common class of heart deformity that is present at birth (congenital cardiac malformation)..
    Septate: Divided: A septate uterus is a one that is divided.
    Septate vagina: A vagina that is divided, usually longitudinally, to create a double vagina. This situation can be easily missed by the patient and even by the doctor on exam. If the patient becomes sexually active prior to diagnosis, one of the vaginas stretches and becomes "dominant". The other vagina slips slightly upward and flush and is a little difficult to enter.
    Septic bursitis: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known as "bursitis." When the bursa is infected with bacteria, the condition is called septic bursitis.
    Septum: A word borrowed from the Latin "saeptum" meaning a "dividing wall or enclosure."
    Septum, interatrial: The wall separating the upper chambers (the atria) of the heart. A hole in the interatrial septum is termed an atrial septal defect (ASD).
    Septum, interventricular: The wall separating the lower chambers (the ventricles) of the heart. A hole in the interventricular septum is termed a venticular septal defect (VSD).
    Septum, nasal: The dividing wall that runs down the middle of the nose so that there are normally two sides to the nose, each ending in a nostril.
    Sequence, complementary: Nucleic acid sequence of bases that can form a double- stranded structure by matching base pairs. For example, the complementary sequence to C-A-T-G (where each letter stands for one of the bases in DNA) is G-T-A-C.
    Sequence, conserved: A base sequence in a DNA molecule (or an amino acid sequence in a protein) that has remained essentially unchanged throughout evolution.
    Sequence, regulatory: A sequence of bases in DNA that controls the expression of a gene.
    Sequence tagged site (STS): A short (200 to 500 base pairs) DNA sequence that occurs but once in the human genome and whose location and base sequence are known. Detectable by polymerase chain reaction, STSs are useful for localizing and orienting the mapping and sequence data reported from many different laboratories and serve as landmarks on the developing physical map of the human genome. Expressed sequence tags (ESTs) are STSs derived from comlementarty DNAs (cDNAs).
    Sequencing: Learning the order of nucleotides (base sequences) in a DNA or RNA molecule or the order of amino acids in a protein.
    SERM: Selective Estrogen-Receptor Modulator.
    Serositis: Inflammation of the serous tissues of the body. The serous tissues line the lungs (pleura), heart (pericardium), and the inner lining of the abdomen (peritoneum) and organs within.
    Serotonin: A chemical in the brain involved in the transmission of nerve impulses. Serotonin.can trigger the release of substances in the blood vessels of the brain that in turn cause the pain of the migraine.
    Serum: The clear liquid that separates from clotted blood. Serum differs from plasma, the liquid that separates from unclotted blood. "Serum" is the Latin word for "whey", the watery liquid that separates from the curds in > cheesemaking.
    Serum hepatitis: An obsolete term. See Hepatitis B.
    Sexually transmitted disease (STD): Any disease transmitted by sexual contact. Examples: gonorrhea, syphilis, AIDS.. The older term was venereal disease.
    Sexually transmitted diseases in women: Gonorrhea and chlamydia are bacterial sexually transmitted diseases (STDs) frequently found together. Gonorrhea is NOT transmitted from toilet seats. Women infected with it may not have any symptoms but can end up later with severe pelvic infection. Early syphilis causes a mouth or genital ulcer (chancre) and later can cause hair loss, headaches, sore throat, and skin rash. Even later, syphilis can lead to heart and brain damage. Genital herpes is a viral infection that can cause painful genital sores. Genital warts are caused by viruses and can increase a woman’s risk for cancer of the cervix. AIDS is caused by the human immunodeficiency virus (HIV). Hepatitis B is a virus that causes liver inflammation and can lead to cirrhosis and cancer of the liver. Hepatitis B can now be prevented with a vaccine. There is no "safe" sex. Condoms do not necessarily prevent STDs.
    Shell shock: The World War I name for what is known today as post-traumatic stress, this is a psychological disorder that develops in some individuals who have had major traumatic experiences (and, for example, have been in a serious accident or through a war). The person is typically numb at first but later has symptoms including depression, excessive irritability, guilt (for having survived while others died), recurrent nightmares, flashbacks to the traumatic scene, and overreactions to sudden noises. Post-traumatic stress became known as such in the 70s due to the adjustment problems of some Vietnam veterans.
    Shin bone fever: A louse-borne disease first recognized in the trenches of World War I, again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Also called trench fever, Wolhynia fever, quintan fever, five-day fever, Meuse fever, His’ disease, His-Werner disease, Werner-His disease.
    Shingles: Shingles is an acute infection by a virus called Herpes zoster, which causes an eruption of vesicles in the skin. The eruption is usually distributed along the area of the skin that is innervated by a nerve that supplies sensation. The pain associated with shingles is, in part, related to inflammation of the associated sensory nerve.

    Shock: In medicine, shock is a critical condition brought on by a sudden drop in blood flow through the body. There is failure of the circulatory system to maintain adequate blood flow. This sharply curtails the delivery of oxygen and nutrients to vital organs. It also compromises the kidney and so curtails the removal of wastes from the body. Shock can be due to a number of different mechanisms including not enough blood volume (hypovolemic shock) and not enough output of blood by the heart (cardiogenic shock). The signs and symptoms of shock include low blood pressure (hypotension), overbreathing (hyperventilation), a weak rapid pulse, cold clammy grayish-bluish (cyanotic) skin, decreased urine flow (oliguria), and mental changes (a sense of great anxiety and forboding, confusion and, sometimes, combativeness). Shock is a major medical emergency.
    Shock, cardiogenic: Shock caused by heart failure. The heart fails to pump blood effectively. For example, a heart attack (a myocardial infarction) can cause an abnormal ineffectual heart beat (an arhythmia) with very slow, rapid, or irregular contractions of the heart, impairing the heart’s ability to pump blood, lowering the volume of blood going to vital organs. Cardiogenic shock can also be due to drugs that reduce heart function or an abnormally low level oxygen in the blood (hypoxemia) caused, for instance, by lung disease. Whatever be the cause, blood vessels constrict and adrenalin-like substances are secreted into the bloodstream, increasing the heart rate. Treatment of cardiogenic shock is aimed at improving the heart’s function. Shock after a heat attack is extremely serious. The mortality rate is over 80%.
    Shock, hypovolemic: Shock due to a decrease in blood volume. This is the #1 cause of shock. It can be due to loss of blood from bleeding, loss of blood plasma through severe burns, and dehydration. The treatment, first and foremost, is prompt intravenous administration of fluid.
    Shock, psychologic: Trauma due to psychological events, as in "shell shock" (now known as post-traumatic stress disorder).
    Shock, shell: The World War I name for what is known today as post-traumatic stress, this is a psychological disorder that develops in some individuals who have had major traumatic experiences (and, for example, have been in a serious accident or through a war). The person is typically numb at first but later has symptoms including depression, excessive irritability, guilt (for having survived while others died), recurrent nightmares, flashbacks to the traumatic scene, and overreactions to sudden noises. Post-traumatic stress became known as such in the 70s due to the adjustment problems of some Vietnam veterans.Shots, allergy: Known medically as allergy desensitization or allergy immunotherapy, the injections are designed to stimulate the immune system with gradually increasing doses of the substances to which a person is allergic, the aim being to modify or stop the allergy "war" (by reducing the strength of the IgE and its effect on the mast cells). This form of treatment is very effective for allergies to pollen, mites, cats, and especially stinging insects (eg, bees, hornets, yellowjackets, wasps, velvet ants, fire ants). Allergy immunotherapy usually takes 6 months to a year to become effective and injections are usually required for 3-5 years.
    Shock, toxic: See Syndrome, toxic shock.
    Shots, allergy: Known medically as allergy desensitization or allergy immunotherapy, the injections are designed to stimulate the immune system with gradually increasing doses of the substances to which a person is allergic, the aim being to modify or stop the allergy "war" (by reducing its effect on the mast cells). This form ofhe strength of the IgE and its treatment is very effective for allergies to pollen, mites, cats, and especially stinging insects (eg, bees, hornets, yellowjackets, wasps, velvet ants, fire ants). Allergy immunotherapy usually takes 6 months to a year to become effective and injections are usually required for 3-5 years.
    Shoulder bursitis: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are two major bursae of the shoulder. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery.
    Show: An appearance.
    Show, bloody: Literally, the appearance of blood. The bloody show consists of blood-tinged mucus created by extrusion and passage of the mucous plug that filled the cervical canal (the canal between the vagina and uterus) during pregnancy. The bloody show is a classic sign of impending labor. The same term, bloody show, can be applied to the beginning of menstruation.
    Shprintzen syndrome: Congenital malformation (birth defect) syndrome with cleft palate, heart defect, abnormal face, and learning problems. The condition is also called the velo-cardio-facial (VCF) syndrome. (The velum is the soft palate). Other less frequent features include short stature, small-than-normal head (microcephaly), mental retardation, minor ear anomalies, slender hands and digits, and inguinal hernia. The cause is usually a microdeletion in chromosome band 22q11.2, just as in DiGeorge syndrome. Shprintzen and DiGeorge syndromes are different clinical expressions of essentially the same chromosome defect.
    Shulman’s syndrome (Eosinophilic fasciitis): A disease which leads to inflammation and thickening of the skin and fascia. (The fascia is a lining tissue under the skin that covers a surface of underlying tissues. When the fascia is inflamed, the condition is referred to as "fasciitis.") In eosinophilic fasciitis, the involved fascia is inflamed with the eosinophil white blood cells. There is progressive thickening, and often redness and warmth, and hardness of the skin surface.
    Shunt: A catheter (tube) that carries cerebrospinal fluid from a ventricle in the brain to another area of the body.
    Side effects: Problems that occur when treatment affects healthy cells. Common side effects of cancer treatment are fatigue, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.
    SIDS (Sudden Infant Death Syndrome): The sudden and unexpected death of a baby with no known illness, typically affecting infants from 2 weeks to 6 months of age while sleeping. At elevated risk for SIDS are children with a brother or sister who died of SIDS; babies whose mothers smoked or used heroin, methadone, or cocaine during pregnancy; infants born weighing less than 4.4 pounds (2000 grams); children with an abnormal breathing pattern with long periods without taking a breath (apnea); and babies who sleep on their stomachs. Since babies who sleep on their stomachs are at least 3 times more likely to die of SIDS than babies who sleep on their backs, children’s health authorities such as the American Academy of Pediatrics recommend always placing infants on their backs to sleep.
    Sigmoidoscope: A lighted instrument used to view the inside of the lower colon.

    Sigmoidoscopy: Sigmoidoscopy is a procedure whereby a doctor inserts a viewing tube (sigmoidoscope) into the rectum for the purpose of inspecting the lower colon (sigmoid colon) and rectum. If an abnormal area is detected, a biopsy can be performed.
    Sign: Any abnormality, such as a change in appearance, sensation, or function, observed by a physician when evaluating a patient which indicates a disease process.
    Single-gene diseases: Hereditary disorders caused by a change (mutation) in a single gene. There are thousands of single-gene diseases including achondroplastic dwarfism, Huntington disease, cystic fibrosis, sickle cell disease, Duchenne muscular dystrophy, and hemophilia. Single-gene diseases typically describe classic simple Mendelian patterns of inheritance (as autosomal dominant, autosomal recessive, and X-linked traits) by comparison with polygenic diseases.
    Sino-atrial node: See SA node.
    Sinus tachycardia: Fast heartbeat (tachycardia) occurring because of rapid firing by the SA node, the natural pacemaker of the heart. Electrical signals initiated in the SA node are transmitted to the atria and the ventricles to stimulate heart muscle contractions heartbeats. Sinus tachycardia is usually a rapid contraction of a normal heart in response to a condition, drug, or disease as, for examples, pain, fever, excessive thyroid hormone, exertion, excitement, low blood oxygen level (hypoxia), or stimulant drugs such as caffeine, cocaine, and amphetamines. However, in some cases, it can be a sign of heart failure, heart valve disease, or other illness.
    Sinusitis: Sinusitis is inflammation of the lining membrane of any of the hollow areas (sinuses) of the bone of the skull around the nose. The sinuses are directly connected to the nasal cavities.
    Situs inversus totalis: A condition in which there is complete transposition (right to left reversal) of the thoracic and abdominal organs. The heart is not in its usual position in the left chest but is on the right. Specifically related to the heart, this is referred to as dextrocardia (literally, right-hearted). And the stomach, which is normally in the left upper abdomen, is on the right. In patients with situs inversus totalis, all of the chest and abdominal organs are reversed and appear in mirror image when examined or visualized by tests such as x-ray filming. Situs inversus totalis has been estimated to occur once in about 6-8,000 births. Situs inversus occurs in a rare abnormal condition that is present at birth (congenital) called Kartagener’s syndrome.
    Sixth disease: A viral disease of infants and young children with sudden onset of high fever which lasts several days and then suddenly subsides leaving in its wake a fine red rash. The causative agent is herpesvirus type 6 so the disease is known as Sixth Disease. Also known as Exanthem subitum (sudden rash), Pseudorubella, Roseola, Roseola infantilis, and Roseola infantum.
    Skeletal dysplasia: One of a large contingent of genetic diseases in which the bony skeleton is abnormally formed during development. For example, achondroplasia (achondroplastic dwarfism).
    Skeletal muscle: One of three types of muscle tissue in the body (skeletal, smooth, cardiac) which represents the majority of the muscular tissue in the body. Skeletal muscle is the type of muscle which powers movement of the skeleton as in walking and lifting.
    Skeleton: The skeleton is composed of bones and is the framework of the body.
    Skin graft: Skin that is moved from one part of the body to another.
    Skin, scalded, syndrome: See Scalded skin syndrome.
    Skin test for allergy: Test done on the skin to identify the allergy substance (allergen) triggering the allergic reaction. A small amount of the suspected allergy substance is placed on the skin. The skin is then gently scratched through the small drop with a special sterile needle. If the skin reddens and, more importantly, swells, then allergy to that substance is probable.
    Skull: The skull is a collection of bones which encases the brain and gives form to the head and face. These bones include the following - frontal, parietal, occipital, temporal, sphenoid, ethmoid, zygomatic, maxilla, nasal, vomer, palatine, inferior concha, and mandible.
    Slanted ear: An ear that is slanted more than usual. Technically, an ear is slanted when the angle of the slope of the auricle is more than 15 degrees from the perpendicular. Considered a minor anomaly. The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Sleep apnea: Temporary stoppage of breathing during sleep, often resulting in daytime sleepiness.
    Small cell lung cancer: A type of lung cancer in which the cells are small and round. Also called oat cell lung cancer.
    Small intestine: The part of the digestive tract that extends from the stomach to the large intestine.
    Smoldering leukemia: A condition in which the bone marrow does not function normally. It does not produce enough blood cells. This condition may progress and become acute leukemia. Smoldering leukemia also is called myelodysplastic syndrome or preleukemia.
    Smooth muscle: One of the three types of muscle tissue in the body (skeletal, smooth, cardiac). Generally forms the supporting tissue of blood vessels and hollow internal organs such as the stomach, intestine, and bladder. So named because of the absence of microscopic lines called "cross-striations" which are seen in the other two types.
    Snoring: During normal breathing, air passes through the throat en route to the lungs and travels by the tongue, soft palate (the back of the roof of the mouth), uvula (the prominent anatomic structure dangling downward visibly at the back of the mouth), and tonsils. When a person is awake, the muscles in the back of the throat tighten to hold these structures in place and prevent them from collapsing and vibrating in the airway. During sleep, the uvula and soft palate frequently vibrate causing the sounds of snoring.
    Soft palate: The muscular part of the roof of the mouth. The soft palate is directly behind the hard palate. It lacks bone and so is soft.
    Soft tissue sarcoma: A sarcoma that begins in the muscle, fat, fibrous tissue, blood vessels, or other supporting tissue of the body. Not a type of bone cancer.
    Somnoplasty: A surgical treatment for snoring. Somnoplasty uses heat energy to remove tissues of the uvula and soft palate. (See: Snoring). Somnoplasty is usually done as an office procedure with local anesthesia. It is not indicated for the treatment of sleep apnea.
    Spasmodic dysphonia: Involves the muscles of the throat that control speech. Also called spastic dysphonia or laryngeal dystonia, it causes strained and difficult speaking or breathy and effortful speech.
    Spastic colitis: See Syndrome, irritable bowel.
    Spastic pseuodoparalysis: Better known as Creutzfeldt-Jakob disease (CJD). A dementing disease of the brain. It is believed due to an unconventional (not a bacteria or virus), transmissible agent called a prion. Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Creutzfeldt-Jakob syndrome and Jakob-Creutzfeldt disease.
    Speculum: An instrument used to widen the opening of the vagina so that the cervix is more easily visible.

    Speech pathologist: A specialist who evaluates and treats people with communication and swallowing problems. Also called a speech therapist.
    Sperm: A sperm is the male "gamete" or sex cell. It combines with the female "gamete," called an ovum, to form a zygote. The formation process is called "fertilization." (see ovum, zygote).
    Spermatic cord: A group of structures which go through the inguinal canal to the testis. The structures include the vas deferens, arteries, veins, lymphatic vessels, and nerves.
    Spina bifida: A bony defect in the vertebral column through which the meningeal membrane and spinal cord may protrude (spina bifida cystica) or may not protrude so that the defect remains hidden, covered by skin (spina bifida occulta). Spina bifida cystica, also known as meningomyelocele (MM), is due to failure of closure during embryonic life of bottom end of the neural tube, the structure which gives rise to the central nervous system (the brain and spinal cord). The term spina bifida refers specifically only to the bony defect in the vertebral column but, through usage, the term spina bifida is gradually becoming synonymous with MM. The risk of spina bifida (and all neural tube defects) can be decreased by the mother eating ample folic acid during pregnancy.
    Spina bifida cystica: A bony defect in the vertebral column through which the meningeal membranes that cover the spinal cord and part of the spinal cord protrude. An alternative term is meningomyelocele.
    Spina bifida occulta: Literally, a hidden cleft in the spine. A bony defect in the vertebral column which remains hidden, covered by skin
    Spine: Commonly, a reference to the bony building blocks of bone (vertebral column) surrounding and protecting the spinal cord. The spine can be categorized according to level of the body, i.e., cervical spine (neck), thoracic spine (upper and mid-back), and lumbar spine (low back). A spine also refers to a short prominence of bone. It is the spines of the vertebrae that we can feel protruding at the base of the back of our neck and in the middle of our backs. These spines protect our spinal cord from injury from behind.
    Spirochete: A microscopic bacterial organism, a spirochete apperars worm-like, spiral-shaped, and wiggles vigorously when viewed under a microscope. Treponema pallidum, the cause of syphilis, is a particularly well-known member of the Spirochaeta family. The term spirochete is an odd hybrid of Greek and Latin roots, the Latin "spira" for "coil" and the Greek "chaite" for "long flowing hair," formed because the spirochete looked like a coil of hair.
    Spleen: The spleen is a blood vessel filled organ located in the upper left abdominal cavity. It is a storage organ for red blood cells and contains many specialized white blood cells called "macrophages" which act to filter blood.
    Spleen, ruptured: Rupture of the capsule of the spleen, an organ in the upper left part of the abdomen, is a potential catastrophe that requires immediate medical and surgical attention. Splenic rupture permits large amounts of blood to leak into the abdominal cavity which is severely painful.and life-threatening. Shock and, ultimately, death can result. Patients typically require an urgent operation. Rupture of a normal spleen can be caused by trauma, for example, in an accident. If an individual’s spleen is enlarged, as is frequent in mononucleosis, most physicians will not allow activities (such as major contact sports) where injury to the abdomen could be catastrophic.
    Splenectomy: An operation to remove the spleen.
    Splenic fever: Known also as anthrax, splenic fever is a serious bacterial infection. It is not primarily a human disease but rather an infection of animals. Cattle, sheep, horses, mules, and some wild animals are highly susceptible. Humans (and swine) are generally resistant to anthrax. Anthrax can take different forms. With the lung form of the disease. People inhale the anthrax spores and, if untreated, are likely to die. An intestinal form is caused by eating meat contaminated with anthrax. But most human anthrax comes from skin contact with animal products. Cutaneous (skin) anthrax was once well known among people who handled infected animals, like farmers, > woolsorters, tanners, brushmakers and carpetmakers in the days when the brushes and carpets were animal products. The hallmark of skin anthrax is a carbuncle, a cluster of boils, that ulcerates in an ugly way. Typically, this lesion has a hard black center surrounded by bright red inflammation. This accounts for its name, "anthrax", the Greek word for "coal."
    Spondylolisthesis: Forward movement of one building block of the spine (vertebra) in relation to an adjacent vertebra.
    Spotted fever: Rocky Mountain spotted fever (RMSF):, an acute febrile (feverish) disease initially recognized in the Rocky Mountain states, caused by Rickettsia rickettsii transmitted by hard-shelled (ixodid) ticks. Occurs only in the Western Hemisphere. Anyone frequenting tick-infested areas is at risk for RMSF. Onset of symptoms is abrupt with headache, high fever, chills, muscle pain. and then a rash. The rickettsiae grow within damaged cells lining blood vessels which may become blocked by clots. Blood vessel inflammation (vasculitis) is widespread Early recognition of RMSF and prompt antibiotic treatment is important in reducing mortality. Also called tick fever, and tick typhus.
    Sprue, nontropical: This condition results from an immune (allergic) reaction to gluten, a protein found in wheat and related grains and present in many foods that we eat. Sprue causes impaired absorption and digestion of nutrients through the small intestine. Symptoms include requent diarrhea and weight loss. A skin condition called dermatitis herpetiformis can be associated with celiac sprue. The most accurate diagnostic test for sprue is a biopsy of the involved small bowel. Treatment is to avoid gluten in the diet. Medications are used for refractory (stubborn) sprue. Known under a number of other names, including celiac sprue.
    Spurs, heel: Pointed bony outgrowths at the back of the heel or under the heel beneath the sole of the foot. Heel spurs at the back of the heel are associated with inflammation of the Achilles tendon (tendinitis) and cause tenderness and pain at the back of the heel made worse while pushing off the ball of the foot.
    Sputum: Mucus from the lungs.
    Squamous cells: Flat cells that look like fish scales; they make up most of the epidermis, the outer layer of the skin.
    Squamous cell carcinoma: Cancer that begins in squamous cells, which are thin, flat cells resembling fish scales. Squamous cells are found in the tissue that forms the surface of the skin, the lining of the hollow organs of the body, and the passages of the respiratory and digestive tracts.
    Squamous intraepithelial lesion: A general term for the abnormal growth of squamous cells on the surface of the cervix. The changes in the cells are described as low grade or high grade, depending on how much of the cervix is affected and how abnormal the cells are. Also called SIL.
    Stage: The extent of a cancer, especially whether the disease has spread from the original site to other parts of the body.
    Staging: Doing exams and tests to learn the extent of a cancer, especially whether it has spread from its original site to other parts of the body.
    STD: Sexually transmitted disease.
    STDs in women: See Sexually transmitted diseases in women.
    Staph: Very commonly used shortened form of Staphylococcus, a very common and important group of bacteria. See Staphylococcus.
    Staphyloccoccal scalded skin syndrome: See Scalded skin syndrome.

    Staphylococcus: A group of bacteria, familiarly known as Staph, that can > (and do) cause a multitude of diseases. The name comes from the Greek staphyle meaning a bunch of grapes + kokkos meaning berry, and that is exactly what Staph look like under the microscope, like a bunch of grape or little round berries. (In technical terms, these are gram-positive, facultative anaerobic, usually unencapsulated cocci). Staph can cause illness directly by infection or indirectly through products they make such as toxins responsible for food poisoning and toxic shock syndrome.
    STAT: A common medical abbreviation which is used to imply urgent or rush. It is derived from a latin word "statim" which means immediately.
    Stein-Leventhal syndrome: Known descriptively as polycystic ovarian disease (PCO), this syndrome is basically an hormonal problem that causes women to have a variety of symptoms including irregular or no periods, acne, obesity and excessive hair growth. Women with PCO are at a higher risk for uterine cancer (endometrial cancer), diabetes, high blood pressure, and heart disease. With proper treatment, risks can be minimized. The syndrome is named after the late American gynecologists Irving F. Stein, Sr. and Michael Leo Leventhal.
    Stereotaxis: Use of a computer and scanning devices to create three-dimensional pictures. This method can be used to direct a biopsy, external radiation, or the insertion of radiation implants.
    Steroids: A large group of chemical substances classified by chemical structure. Steroids include drugs used to relieve swelling and inflammation (such as prednisone), vitamin D, and sex steroids (such as testosterone).
    Still’s disease: Also known as systemic-onset juvenile rheumatoid arthritis and systemic-onset juvenile chronic arthritis. Still’s disease presents with systemic (bodywide) illness including high intermittent fever, a salmon-colored skin rash, swollen lymph glands, enlargement of the liver and spleen, and inflammation of the lungs (pleuritis) and around the heart (pericarditis). The arthritis may not be immediately apparent but it does appear in time and may persist after the systemic symptoms are gone. Still’s disease, adult-onset: (See Still’s disease.) Although Still’s disease was first described in children, it is known to occur in adults.
    Stings, insect: Stings from large stinging insects such as yellow jackets, bees, hornets and wasps can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A’s" of insect allergy are Adrenaline, Avoidance and Allergist.)

    Stoma: An opening into the body from the outside created by a surgeon.
    Stomach: A muscular pouch that helps in the digestion of food by mixing it with digestive juices and churning it into a thin liquid.
    Stomach cancer: Cancer of the major organ that holds food for digestion. Stomach cancer (gastric cancer) can develop in any part of the stomach and spread to other organs. Stomach ulcers do not appear to increase a person’s risk of developing stomach cancer. Symptoms of stomach cancer are often vague, such as loss of appetite and weight. The cancer is diagnosed with a biopsy of stomach tissue during a procedure.
    Stomach flu: A misnomer that has nothing to do with influenza (flu) virus, the term "stomach flu" is sometimes used to describe gastrointestinal illnesses caused by other microorganisms.
    Stomach, Pavlov: A pouch fashioned surgically from part of the stomach (but isolated from the rest of the stomach) that opens via a fistula (canal) on to the abdominal wall. At different points along the dogs’ digestive tracts, the Russian physiologist Ivan Petrovich Pavlov (1848-1936) surgically created pockets ("Pavlov pouches") from which he could obtain secretions, the aim being to study the physiology of the digestive tract. He did so from the salivary glands down to the stomach, liver and pancreas with considerable success and in 1904 (the 4th year it was awarded) he received the Nobel Prize for "his work on the physiology of digestion, through which knowledge on vital aspects of the subject has been transformed and enlarged."
    Stool: The solid matter discharged in a bowel movement.
    Stool test: A test to see whether there is blood in the bowel movement. Also called a fecal occult blood test: A test to check for hidden blood in stool. (Fecal refers to stool. Occult means hidden.)
    Strep: Very commonly used shortened form of Streptococcus, a very common and important group of bacteria. See Streptococcus
    Strep throat: An infection caused by a type of bacteria called streptococcus, which can lead to serious complications if not adequately treated.
    Streptococcus: A group of bacteria, familiarly known as strep, that can > (and do) cause a multitude of diseases. The name comes from the Greek strepto- meaning twisted + kokkos meaning berry, and that is exactly what Strep look like under the microscope, like a twisted bunch of little round berries. (In technical terms, these are gram-positive, facultative anaerobic cocci). Illness caused by strep includes strep throat, strep pneumonia, scarlet fever, rheumatic fever (and rheumatic heart valve damage) and > glomerulonephritis.
    Stricture, esophagus, acute: A narrowing or closure of the normal opening of the swallowing tube leading to the stomach, usually caused by scarring from acid irritation. Acute, complete obstruction of the esophagus occurs when food (usually meat) is lodged in the esophageal stricture. Patients experience chest pain, and are unable to swallow saliva. Attempts to relieve the obstruction by inducing vomiting at home are usually unsuccessful. Patients with complete esophageal obstruction can breathe, and are not at any risk of suffocation. Endoscopy is usually employed to retrieve the meat and relieve the obstruction.
    Stricture of the esophagus, chronic: A narrowing or closure of the normal opening of the swallowing tube leading to the stomach, usually caused by scarring from acid irritation. A common complication of chronic gastroesophageal reflux disease (GERD). Several procedures are available for stretching (dilating) the strictures without having to resort to surgery. One of the procedures involves placing a deflated balloon across the stricture at the time of endoscopy. The balloon is then inflated, thereby opening the narrowingcaused by the stricture. Another method involves inserting tapered dilators of different sizes through the mouth into the esophagus to dilate the stricture.
    STS: Sequence tagged site, a short (200 to 500 base pairs) DNA sequence that occurs but once in the human genome and whose location and base sequence are known. Detectable by polymerase chain reaction, STSs are useful for localizing and orienting the mapping and sequence data reported from many different laboratories and serve as landmarks on the developing physical map of the human genome. Expressed sequence tags (ESTs) are STSs derived from cDNAs (complementary DNAs).
    Study, cross-sectional: A study done at one time, not over the course of time. A cross-sectional study a disease such as AIDS might be designed to learn its prevalence and distribution within the population at one point in time. Also known as a synchronic study.
    Study, diachronic: See: Study, longitudinal.
    Study, longitudinal: A study done over the passage of time. For example, a longitudinal study of children with Down syndrome (trisomy 21) might involve the study of 100 children with this condition from birth to 10 years of age. Also called a diachronic study. The opposite of a cross-sectional (synchronic) study.
    Study, synchronic: See: Study, cross-sectional.
    Subglottis: The lower part of the larynx; the area from just below the vocal cords down to the top of the trachea.
    Sublingual gland: The smallest of the three major salivary glands. It is located. It lies under the floor of the mouth close to the midline.
    Subluxation: Partial dislocation of a joint. A complete dislocation is a luxation.
    Submandibular gland: The second largest of the three major salivary glands. It is located deep to the mandible (jaw bone).
    Submaxillary gland: See Submandibular gland.
    Subtotal hysterectomy: The uterus is sugically removed but the cervix is left is left in place. Also called a partial hysterectomy.
    Succenturiate: In anatomy "succenturiate" means substituting for or accessory to an organ. For example, see Succenturiate placenta. Succenturiate placenta: An extra placenta separate from the main placenta. In anatomy "succenturiate" means substituting for or accessory to an organ. In this case, a succenturiate placenta is an accessory placenta.
    Succenturiate placenta: An extra placenta separate from the main placenta. In anatomy "succenturiate" means substituting for or accessory to an organ. In this case, a succenturiate placenta is an accessory placenta.
    Sudden Infant Death Syndrome (SIDS): The sudden and unexpected death of a baby with no known illness, typically affecting infants from 2 weeks to 6 months of age while sleeping. At elevated risk for SIDS are children with a brother or sister who died of SIDS; babies whose mothers smoked or used heroin, methadone, or cocaine during pregnancy; infants born weighing less than 4.4 pounds (2000 grams); children with an abnormal breathing pattern with long periods without taking a breath (apnea); .and babies who sleep on their stomachs. Since babies who sleep on their stomachs are at least 3 times more likely to die of SIDS than babies who sleep on their backs, children’s health authorities such as the American Academy of Pediatrics recommend always placing infants on their backs to sleep.
    Sulcus: From the Latin for a groove, furrow, or trench. In medicine, there are many sulci (plural of sulcus) as, for example, the superior pulmonary sulcus.
    Sun protection factor (SPF): A number on a scale (from 2 upwards) for rating sunscreens. Sunscreens with an SPT of 15 or higher provide the best protection from the sun's harmful rays.

    Sunscreen: A substance that blocks the effect of the sun's harmful rays. Using lotions that contain sunscreens can reduce the risk of skin cancer, including melanoma.
    Supernumerary: Beyond the normal number. Anything supernumerary is extra.
    Supernumerary digit: An extra finger or toe.
    Supernumerary nipple: An extra nipple.
    Supernumerary placenta: A succenturiate or accessory placenta.
    Supination: Rotation of the arm or leg outward. In the case of the arm, the palm of the hand will face forward.
    Supine: Lying on the back.
    Supportive care: Treatment given to prevent, control, or relieve complications and side effects and to improve the patient's comfort and quality of life.
    Supraglottis: The upper part of the larynx, including the epiglottis; the area above the vocal cords.
    Suprarenal gland: See adrenal gland.
    Suprasternal notch: The V shaped notch at the top of the breastbone (sternum).
    Surgery: An operation.
    Suture: This word has several meanings depending on context. 1) A type of bone joint where two bones are held tightly together by fibrous tissue as in the skull. 2) Thread-like material used to sew tissue. 3) To stitch a wound closed.
    Swimming pool granuloma: Localized nodular skin inflammation (small reddish raised areas of skin) caused by a bacterium called mycobacterium marinum. Swimming pool granuloma is typically acquired by occupational or recreational exposure to salt or fresh water, often resulting from minor trauma during caring for aquariums. The diagnosis is suggested by the history of exposure and confirmed by culturing tissue specimens which yield the microscopic organism, mycobacterium marinum. The infection can be treated with a variety of antibiotics, including doxycycline, minocycline, clarithromycin, rifampin, and trimethoprim-sulfamethoxazole. Also called "fish bowl granuloma."
    Sympathetic nervous system: A part of nervous system that serves to accelerate the heart rate, constrict blood vessels, and raise blood pressure. The sympathetic nervous system, together with the parasympathetic nervous system (that slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles), constitutes the autonomic nervous system.
    Symphysiotomy: A surgical procedure to effect an immediate dramatic increase in the size of the pelvic outlet to permit delivery of a baby. The cartilage of the symphysis pubis (where the pubic bones come together) is surgically divided in the procedure which can be a life-saver for the baby.
    Symphysis pubis: The Greek word "symphysis" means growing together. The "pubis" are the pubic bone. So the symphysis pubis is where the pubic bones meet (in the front of the pelvis).
    Symptom: Any abnormal change in appearance, sensation, or function experienced by a patient which indicates a disease process.
    Synchronic: From the Greek syn-, together + chronos, time = together in time. A synchronic study is a study done all together at one point in time rather than longitudinally over the course of time.
    Syncope: Fainting represented by a partial or complete loss of consciousness.
    Syndrome: A syndrome is the combination of symptoms and signs which together represent a disease process.
    Syndrome, acquired immunodeficiency: AIDS.
    Syndrome, antiphospholipid antibody: An immune disorder characterized by the presence of abnormal antibodies in the blood associated with certain medical conditions including abnormal blood clotting, migraine headaches, premature miscarriage, and low blood platelet counts (thrombocytopenia).
    Syndrome, Barlow’s: Barlow’s syndrome is mitral valve prolapse (also known as "click murmur syndrome"), the most common heart valve abnormality, affecting 5-10% of the world population. Most patients have no symptoms and require no treatment. However, the condition can be associated with fatigue and/or palpitations. The mitral valve prolapse can often be detected by a doctor during examination of the heart and can be confirmed with an echocardiogram. Patients are usually given antibiotics prior to any procedure which might introduce bacteria into the bloodstream, including dental work and minor surgery.
    Syndrome, Behcet’s: Behcet’s syndrome is classically characterized as a triad of symptoms that include recurring crops of mouth ulcers (called apthous ulcers), genital ulcers, and inflammation of a specialized area around the pupil of the eye, the uvea. (The inflammation is called uveitis.) The cause of Behcet’s syndrome is not known. The disease is more frequent and severe in patients from the Eastern Mediterranean and Asia than those of European descent.

    Syndrome, Bernard: A complex of abnormal findings, namely sinking in of one eyeball, ipsilateral ptosis (drooping of the upper eyelid on the same side) and miosis (constriction of the pupil of that eye) together with anhidosis (lack of sweating) and flushing of the affected side of the face. Due to paralysis of certain nerves (specifically, the cervical sympathetic nerves). Also called Horner-Bernard syndrome, Bernard-Horner syndrome and Horner’s ptosis but best known today as Horner syndrome.
    Syndrome, Bloch-Sulzberger: Also known as incontinentia pigmenti (IP). A genetic disease with blisters that develop soon after birth on the trunk and limbs, then heal, but leave dark (hyperpigmented) streaks and marble-like whorls on the skin. (The name came from the erroneous idea that the skin cells were incontinent of pigment and could not contain it normally.) Other key features of IP include dental and nail abnormalities, bald patches, and (in about 1/3rd of cases) mental retardation. IP is an X-linked dominant with male lethality. The IP gene is in band q28 on the X chromosome. Mothers with IP have an equal chance of having a normal or IP daughter or a normal son. The IP sons die before birth. IP is also known as Bloch-Sulzberger syndrome.
    Syndrome, Conn’s: Overproduction of the hormone aldosterone from a tumor containing tissue like that in the outer portion (cortex) of the adrenal gland. Excess aldosterone (pronounced al-do-ster-one) results in low potassium levels (hypokalemia), underacidity of the body (alkalosis), muscle weakness, excess thirst (polydipsia), excess urination (polyuria), and high blood pressure (hypertension). Also called primary aldosteronism and hyperaldosteronism. Named after the American physician Jerome W. Conn.
    Syndrome, cracked tooth: A toothache caused by a broken tooth (tooth fracture) without associated cavity or advanced gum disease. Biting on the area of tooth fracture can cause severe sharp pains. These fractures are usually due to chewing or biting hard objects such as hard candies, pencils, nuts, etc. Sometimes, the fracture can be seen by painting a special dye on the cracked tooth. Treatment usually is to protect the tooth with a crown. However, if placing a crown does not relieve pain symptoms, a root canal procedure may be necessary.
    Syndrome, Creutzfeldt-Jakob: Better known as Creutzfeldt-Jakob disease (CJD). A dementing disease of the brain. It is believed due to an unconventional (not a bacteria or virus), transmissible agent called a prion. Symptoms of CJD include forgetfulness, nervousness, jerky trembling hand movements, unsteady gait, muscle spasms, chronic dementia, balance disorder, and loss of facial expression. CJD is classified as a spongiform encephalopathy. Most cases occur randomly (sporadically), but inherited forms exist. There is neither treatment nor cure for CJD. Other names for CJD include Jakob-Creutzfeldt disease and spastic pseuodoparalysis.
    Syndrome, Cushing’s: The constellation of symptoms and signs caused by an excess of cortisol hormone. Cushing syndrome is an extremely complex hormonal condition that involves many areas of the body. Common symptoms are thinning of the skin, weakness, weight gain, bruising, hypertension, diabetes, thin weak bones (osteoporosis), facial puffiness, and in women cessation of periods. Ironically, one of the commonest causes of Cushing’s syndrome is the administration of "cortisol-like medications" for the treatment of diverse diseases. All other cases of Cushing’s syndrome are due to excess production of cortisol by the adrenal gland including 1) an abnormal growth of the pituitary gland, which stimulates the adrenal gland, 2) a benign or malignant growth within the adrenal gland itself, which produces cortisol and 3) production within another part of the body (ectopic production) of a hormone that directly or indirectly stimulates the adrenal gland to make cortisol. Neurosurgeon Harvey Cushing (1869-1939) described hyperadrenocorticism (excessive production of cortisol by the adrenal gland) due quite specifically to an ACTH-secreting pituitary adenoma, a benign pituitary tumor that puts out ACTH (AdrenoCorticoTropic Hormone) which, in turn, drives (or overdrives) the adrenal gland to overproduce cortisol.
    Syndrome, DiGeorge (DGS): This disorder is characterized by (1) low blood calcium levels (hypocalcemia) due to underdevelopment (hypoplasia) of the parathyroid glands which control calcium; (2) underdevelopment (hypoplasia) of the thymus, an organ behind the breastbone in which lymphocytes mature and multiply; and (3) defects of the heart involving the outflow tracts from the heart. Most cases of DGS are due to a microdeletion in chromosome band 22q11.2. A small number of cases have defects in other chromosomes, notably 10p13. Named after the American pediatric endocrinologist Angelo > DiGeorge. Other names for DGS include the third and fourth pharyngeal pouch syndrome and hypoplasia of the thymus and parathyroids.
    Syndrome, Down: A common disorder due to a chromosome abnormality and specfically due to an extra chromosome number 21 (trisomy 21). Down syndrome includes mental retardation, a characteristic face, and multiple malformations. It is associated with a major risk for heart problems, a lesser risk of duodenal atresia (part of the intestines not developed), and a minor but still significant risk of acute leukemia. The name Down syndrome comes from the 19th century English doctor Langdon Down, a misnomer since he was curiously enough not the first person to describe the condition and, in great error, attributed the condition to a "reversion" to the mongoloid race. Hence, the old name mongolism, now considered slang.

    Syndrome, dumping: A group of symptoms that occur when food or liquid enters the small intestine too rapidly. These symptoms include cramps, nausea, diarrhea, and dizziness.
    Syndrome, Edwards: This is trisomy 18 syndrome. There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is profound with the IQ too low to even test. Nineteen out of 20 (95%) of these children die before their first birthday. The condition is named after the British physician and > geneticist John Edwards who discovered the extra chromosome in 1960.
    Syndrome, fetal alcohol (FAS): The sum total of a person’s problems caused by maternal alcohol intake during pregancy.
    Syndrome, fish-odor: An inborn error of metabolism associated with an offensive body odor, the smell of rotting fish, due to the excessive excretion of trimethylaminuria (TMA) in urine, sweat, and breath. Persons with TMA may experience tachycardia (fast heart rate) and severe hypertension (high blood pressure) after eating cheese (which contains tyramine) and after using nasal sprays containing epinephrine. TMA is caused by a mutation (change) in the gene for an enzyme, flavin-containing monooxygenase-3 (FMO3) encoded by a gene on chromosome #1. The FMO3 enzyme metabolizes tyramine (which is in cheese). The syndrome is associated with various psychosocial reactions, including social isolation, clinical depression and attempted suicide.

    Syndrome, floppy baby: Floppy baby syndrome is a general medical reference to an abnormal condition of newborns and infants manifest by inadequate tone of the muscles. Hypotonia (inadequately toned muscles resulting in floppiness) in the newborn period and infancy can be due to a multitude of different neurologic and muscle problems.
    Syndrome, fragile X: The most common heritable form of mental retardation. Fragile X syndrome is due to mutation (changes) at the fragile X site and so perforce is X-linked (carried on the X chromosome). Although it is usually more severe in males than females, the syndrome is due to a dynamic mutation (a trinucleotide repeat) that can change in length and hence in severity from generation to generation, from person to person, and even within a given person. The fragile X syndrome is also known as the Martin-Bell syndrome in honor of their discovery of it in 1943.
    Syndrome, Hecht: Inherited disorder transmitted as an autosomal dominant trait in which short tight muscles make it impossible to open the mouth fully or keep the fingers straight when the hand is flexed back. The small mouth creates feeding problems. The hands may be so tightly fisted the infant crawls on the knuckles. Also called the trismus pseudocamptodactyly syndrome.
    Syndrome, Horner: A complex of abnormal findings, namely sinking in of one eyeball, ipsilateral ptosis (drooping of the upper eyelid on the same side) and miosis (constriction of the pupil of that eye) together with anhidosis (lack of sweating) and flushing of the affected side of the face. Due to paralysis of certain nerves (specifically, the cervical sympathetic nerves). Also called Horner-Bernard syndrome, Bernard syndrome, Bernard-Horner syndrome and Horner’s ptosis but far and away best known as Horner syndrome.
    Syndrome, Hurler: A genetic error of metabolism. There is incomplete breakdown and accumulation of a substance (a mucopolysaccharide) which is abnormally stored in the brain and other places. This usually leads to death of the individual with Hurler syndrome by their early teen years. See gargoylism.
    Syndrome, incontinentia pigmenti (IP): A genetic disease with blisters that develop soon after birth on the trunk and limbs, then heal, but leave dark (hyperpigmented) streaks and marble-like whorls on the skin. (The name came from the erroneous idea that the skin cells were incontinent of pigment and could not contain it normally.) Other key features of IP include dental and nail abnormalities, bald patches, and (in about 1/3rd of cases) mental retardation. IP is an X-linked dominant with male lethality. The IP gene is in band q28 on the X chromosome. Mothers with IP have an equal chance of having a normal or IP daughter or a normal son. The IP sons die before birth. IP is also known as Bloch-Sulzberger syndrome.
    Syndrome, irritable bowel (IBS): A common gastrointestinal disorder (also called spastic colitis, mucus colitis or nervous colon syndrome), IBS is an abnormal condition of gut contractions (motility) characterized by abdominal pain, bloating, mucous in stools, and irregular bowel habits with > alternating diarrhea and constipation, symtoms that tend to be chronic and wax and wane over the years. Although IBS can cause chronic recurrent discomfort, it does not lead to any serious organ problems. Diagnosis usually involves > excluding other illnesses. Treatment is directed toward relief of symptoms and includes high fiber diet, exercise, relaxation techniques, avoidance of caffeine, milk products and sweeteners, and medications.
    Syndrome, joint hypermobility: See Syndrome, hypermobility.
    Syndrome, Kartagener’s : The trio of sinusitis, bronchitis and situs inversus (lateral reversal of the position all organs in the chest and abdomen with the heart and stomach on the right, the liver on the left, etc.—opposite or "inverted" from their usual position).
    Syndrome, kinky hair: Genetic disorder with fragile twisted ("kinky") hair and progressive deterioration of the brain. Due to an error in copper transport resulting in copper deficiency. Females are carriers and their sons with the gene have the disease. Also known as Menkes syndrome.
    Syndrome, Klinefelter: The most common single cause of hypogonadism (underfunction of the gonads) and infertility in men, Klinefelter syndrome is due to a chromosome abnormality with XXY (plus additional X or Y chromosomes). It affects about 1 in 500 males and results in small testes (hypogenitalism), underproduction of testosterone and infertility (hypogonadism), and a long-limbed, long-trunked, relatively tall, slim build. Klinefelter boys tend to have learning and/or behavioral problems. At adolescence there is little growth of facial hair and a third of boys develop gynecomastia (enlargement of the male breast). Named for the physician Harry Klinefelter who with E.C. Reifenstein, Jr. and Fuller Albright (the founder of modern endocrinology) described the condition in 1942 long before its chromosomal basis became known.
    Syndrome, Klippel-Feil: The combination of short neck, low hairline at the nape of the neck and limited movement of the head. It is due to a defect in the early development of the spinal column in the neck (the cervival vertebrae). The condition is also called the Klippel-Feil sequence (referring to an embryologic or early developmental sequence of events).
    Syndrome, Li-Fraumeni: A family tendency to cancers due to a mutation in a gene that normally serves to curb cancer: the p53 tumor-suppressor gene. Named after Drs. Fred Li and Joe Fraumeni.
    Syndrome, Lennnox: See Syndrome, Lennox-Gastaut.
    Syndrome, Lennox-Gastaut: A severe form of epilepsy that usually begins in early childhood and is characterized by frequent seizures of multiple types, mental impairment, and a particular brain wave pattern (a slow spike-and-wave pattern). The seizures that are notoriously hard to treat and may lead to falls and injuries can be reduced in frequency by treatment with lamotrigone, a chemically novel antiepileptic drug. The syndrome is named for W.G. Lennox and H. Gastaut who described it.

    Syndrome, Marfan: Inherited disorder with long fingers and toes, dislocation of the lens, and aortic wall weakness and aneurysm. (It has been suggested that Abraham Lincoln had Marfan syndrome.)
    Syndrome, Martin-Bell: Better known as the fragile X syndrome, the most common heritable form of mental retardation. Fragile X syndrome is due to mutation (changes) at the fragile X site and so perforce is X-linked (carried on the X chromosome). Although it is usually more severe in males than females, the syndrome is due to a dynamic mutation (a trinucleotide repeat) that can change in length and hence in severity from generation to generation, from person to person, and even within a given person. The fragile X syndrome is known as the Martin-Bell syndrome in honor of their discovery of it in 1943.
    Syndrome, mucocutaneous lymph node: A syndrome of unknown origin, mainly affecting young children, causing fever, reddening of the eyes > (conjunctivitis), lips and mucous membranes of the mouth, ulcerative gum disease (gingivitis), swollen glands in the neck (cervical > lymphadenopathy), and a rash that is raised and bright red (maculoerythematous) in a glove-and-sock fashion over the skin of the hands and feet which becomes hard, swollen (edematous), and peels off. Also called Kawasaki’s disease.
    Syndrome, Munchhausen: Recurrent feigning of catastrophic illnesses. Named for the fictitious Baron who told tales that were whopping lies.
    Syndrome, myelodysplastic: A condition in which the bone marrow does not function normally. It does not produce enough blood cells. This condition may progress and become acute leukemia. Myelodysplastic syndrome also is called preleukemia or smoldering leukemia.
    Syndrome, nail-patella: Hereditary dominant condition with abnormally formed (dysplastic) or absent nails and absent or underdeveloped (hypoplastic) kneecaps (patellae). Other features include iliac horns (symmetrical bilateral central posterior iliac processes), abnormality of the elbows interfering with full range of motion (pronation and supination) and kidney disease resembling glomerulonephritis which.is often mild but can be progressive and lead to renal failure. The nail-patella gene locus found linked genetically to the ABO blood group in1965 is now known to be in chromosome region 9q34. Also called onychoosteodysplasia, Turner-Kieser syndrome, and Fong disease.
    Syndrome, nervous colon: See Syndrome, irritable bowel.
    Syndrome, Pallister-Killian: Condition with multiple malformations at birth and mental retardation due to isochromosome 12p mosaicism (an abnormal chromosome #12 in some cells).
    Syndrome, Patau: Trisomy 13 syndrome or three chromosome number 13s instead of the normal two. Children with this condition have multiple malformations and mental retardation due to an extra chromosome #13 Named after the late Klaus Patau who described the extra chromosome in 1960. This is trisomy 13 syndrome. There are three rather than the normal two chromosomes #13. Children with this syndrome have multiple malformations and mental retardation due to the extra chromosome #13. The malformations commonly include scalp defects, hemangiomas (blood vessel malformations) of the face and nape of the neck, cleft lip and palate, malformations of the heart and abdominal organs, and flexed fingers with extra digits. The mental retardation is profound. The IQ is untestably low. The majority of trisomy 13 babies die soon after birth or in infancy. Named after the late Klaus Patau who discovered the extra chromosome in 1960.
    Syndrome, Pickwickian: The combination of obesity, somnolence, hypoventilation (underbreathing), and plethoric (red) face named after the "fat and red-faced boy in a state of somnolency" in Charles Dickens’ novel The Pickwick Papers. (The same boy is thought by some to have had Prader-Willi syndrome).
    Syndrome, popliteal pterygium: An inherited condition with a web behind the knee. (A pterygium is a winglike triangular membrane.)
    Syndrome, Prader-Willi: A condition in children with floppiness (hypotonia), obesity, small hands and feet and mental retardation. It is due to loss of part or all of chromosome 15, specifcally the chromosome 15 from the father. The "fat and red-faced boy in a state of somnolency" described by Charles Dickens in his novel The Pickwick Papers is thought by some to have had Prader-Willi syndrome. (The same boy inspired the naming of the Pickwickian syndrome).
    Syndrome premenstrual (PMS): A combination of emotional, physical, psychological, and mood disturbances that occur after ovulation and normally end with the onset of the menstrual flow.
    Syndrome, Proteus: A disturbance of cell growth including benign tumors under the skin, overgrowth of the body, often more on one side than the other (hemihypertrophy), and overgrowth of fingers (macrodactyly). The syndrome is named after the Greek god Proteus the polymorphous who could change his appearance. The "elephant man" (John MerricK) of 19th century England who was thought to have had neurofibromatosis probably had Proteus syndrome.
    Syndrome, radial aplasia-thrombocytopenia: See Syndrome, TAR.
    Syndrome, reflex sympathetic dystrophy (RSDS): A condition that features a group of typical symptoms, including pain (often "burning" type), tenderness, and swelling of an extremity associated with varying degrees of sweating, warmth and/or coolness, flushing, discoloration, and shiny skin.
    Syndrome, Reiter’s: A chronic form of inflammatory arthritis wherein the following three conditions are combined: (1) arthritis; (2) inflammation of the eyes (conjunctivitis); and (3) inflammation of the genital, urinary or gastrointestinal systems.
    Syndrome, Reye’s: A sudden, sometimes fatal, disease of the brain > (encephalopathy) with degeneration of the liver, occurs in children (most cases 4-12 years of age), comes after the chickenpox (varicella) or an influenza-type illness, is also associated with taking medications containing aspirin. The child with Reye’s syndrome first tends to be unusually quiet, lethargic (stuporous), sleepy, and vomiting. In the second stage, the lethargy deepens, the child is confused, combative and delirious. And things get worse from there with decreasing consciousness, coma, seizures, and eventually death. The prognosis (outlook) depends on early diagnosis and control of the increased intracranial pressure. Reye’s syndrome is a good reason to have your child immunized against chickenpox and not give a child aspirin for fever.
    Syndrome, scalded skin: See Scalded skin syndrome.
    Syndrome, Shprintzen: Congenital malformation (birth defect) syndrome with cleft palate, heart defect, abnormal face, and learning problems.The condition is also called the velo-cardio-facial (VCF) syndrome. (The velum is the soft palate). Other less frequent features include short stature, small-than-normal head (microcephaly), mental retardation, minor ear anomalies, slender hands and digits, and inguinal hernia. The cause is usually a microdeletion in chromosome band 22q11.2, just as in DiGeorge syndrome. Shprintzen and DiGeorge syndromes are different clinical expressions of essentially the same chromosome defect. Syndrome, Stein-Leventhal: Known descriptively as polycystic ovarian disease (PCO), this syndrome is basically an hormonal problem that causes women to have a variety of symptoms including irregular or no periods, acne, obesity and excessive hair growth. Women with PCO are at a higher risk for uterine cancer (endometrial cancer), diabetes, high blood pressure, and heart disease. With proper treatment, risks can be minimized. The syndrome is named after the late American gynecologists Irving F. Stein, Sr. and Michael Leo Leventhal.
    Syndrome, Shulman’s (Eosinophilic fasciitis): A disease which leads to inflammation and thickening of the skin and fascia. (The fascia is a lining tissue under the skin that covers a surface of underlying tissues.) When the fascia is inflamed, the condition is referred to as "fasciitis." In eosinophilic fasciitis, the involved fascia is inflamed with the eosinophil white blood cells. There is progressive thickening, and often redness and warmth, and hardness of the skin surface.
    Syndrome, TAR: TAR stands for Thrombocytopenia (low blood platelets) and Aplasia (absence) of the Radius (the long bone on the thumb-side of the forearm), features characterizing this syndrome. There is phocomelia > (flipper-limb) with the thumbs always present. The fibula (the smaller bone in thye lower leg) is often absent. The risk of bleeding from too few platelets is high in early infancy but lessens with age. The condition is inherited in an autosomal recessive trait with one gene (on a non-sex chromosome) coming from each parent to the TAR child. Alternative names include > thrombocytopenia-absent radius syndrome, radial aplasia-thrombocytopenia syndrome, and tetraphocomelia-thrombocytopenia syndrome.
    Syndrome, tempero-mandibular joint: Disorder of the temporo-mandibular joint(TMJ) causing pain usually in front of the ear. Pain in the TMJ can be due to trauma (such as a blow to the face), inflammatory or degenerative arthritis, or by the mandible being pushed back towards the ears whenever the patient chews or swallows. Sometimes, muscles around the TMJ used for chewing can go into spasm, causing head and neck pain and difficulty opening the mouth normally.
    Syndrome, tetraphocomelia-thrombocytopenia: See Syndrome, TAR.
    Syndrome, third and fourth pharyngeal pouch: See Syndrome, DiGeorge.
    Syndrome, thoracic outlet: Condition due to compromise of blood vessels or nerve fibers between the armpit (axilla) and base of the neck.
    Syndrome, thrombocytopenia-absent radius: See Syndrome, TAR.
    Syndrome, TMJ: Disorder of the temporo-mandibular joint (TMJ) causing pain usually in front of the ear. Pain in the TMJ can be due to trauma (such as a blow to the face), inflammatory or degenerative arthritis, or by the mandible being pushed back towards the ears whenever the patient chews or swallows. Sometimes, muscles around the TMJ used for chewing can go into spasm, causing head and neck pain and difficulty opening the mouth normally.
    Syndrome, toxic shock: A grave condition occurring predominantly in menstruating women using tampons, toxic shock is characterized by a highly toxic state (with sudden high fever, vomiting, diarrhea, muscle aching) followed by low blood pressure (hypotension) which can lead to shock (and death). There may be a rash resembling sunburn with peeling of skin. The Channing Laboratory in Boston under Dr. Edw. Kass discovered that toxic shock was due to a toxin produced by Staph (Staphylococcus) aureus bacteria growing under conditions with little or no oxygen. The syndrome occurs rarely in women not using tampons and in men.
    Syndrome, trisomy 13: Condition with three rather than the normal two chromosomes #13. Children born with this syndrome have multiple malformations and mental retardation due to the extra chromosome #13. The congenital malformations (birth defects) commonly include scalp defects, > hemangiomas > (blood vessel malformations) of the face and nape of the neck, cleft lip > and palate, malformations of the heart and abdominal organs, and flexed fingers with extra digits. The mental retardation is profound. The IQ is untestably low. The majority of trisomy 13 babies die soon after birth or in infancy. The condition is also called Patau syndrome after the late geneticist Klaus Patau > (at the University of Wisconsin) who discovered the extra chromosome in 1960.
    Syndrome, trisomy 18: There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is profound with the IQ too low to edven test. Nineteen out of 20 (95%) of these children die before their first birthday. The condition is also called Edwards syndrome in honor of the British physician and geneticist John Edwards who discovered the extra chromosome in 1960.
    Syndrome, trisomy 21: A common chromosome disorder due to an extra chromosome number 21 (trisomy 21). The syndrome causes mental retardation, a characteristic face, and multiple malformations. It is associated with a major risk for heart problems, a lesser risk of duodenal atresia (part of the intestines not developed), and a minor but still significant risk of acute leukemia. Trisome 21 syndr0ome is also commonly called Down syndrome after the 19th century English doctor Langdon Down who was curiously enough not the first person to describe the condition, added little to knowledge and, in great error, attributed the condition to a "reversion" to the mongoloid race. The disorder was also once called mongolism, a term now considered slang.
    Syndrome, Turner-Kieser: See nail-patella syndrome Turner in 1933 described two families with the disease. The name Turner is more closely associated with the XO syndrome.
    Syndrome, yeast: The yeast Candida has been thought to cause a syndrome with a number of nonspecific problems including fatigue, loss of appetite, headache, short-attention span, depression and all manner of intestinal irregularities. There is no scientific evidence to support the existence of the yeast syndrome (also called the yeast connection).
    Synovia: The joint fluid. The term synovia was invented in 1520 by the Swiss physician (and alchemist) Paracelsus who combined the Greek syn-(together) and oon (egg) to create a name for any body fluid that looked like the white of an egg. Today, synovia is restricted to the fluid that lubricates joints.
    Synovial cyst, popliteal: A swelling in the space behind the knee (the popliteal space). The swelling is composed of a membrane-lined sac filled with synovial fluid that has escaped from the joint. Commonly called Baker’s cyst.
    Synovial fluid: The slippery fluid in joints. Also called the synovia.
    Synovial lining: The lining of the joint.
    Synovitis: Inflammation of the synovial membrane, the lining of the joint.
    Syphilis: A sexually transmitted disease (STD) that has been around for centuries and is caused by Treponema pallidum, a microscopic organism called a spirochete, a worm-like spiral-shaped organism that infects by burrowing into the moist mucous membranes of the mouth or genitals. From there, the spirochete produces the classic non-painful ulcer known as a chancre. There are three stages of syphilis. The first ("primary") stage is formation of the chancre. It is highly contagious and can last 1-5 weeks. The disease can be transmitted from any contact with one of the ulcers, which are teeming with spirochetes. If the ulcer is outside of the vagina or on the scrotum of the male, the use of condoms may not help in preventing transmission of the disease. Likewise, if the ulcer is in the mouth, merely kissing the infected individual can spread syphilis. Even without treatment, the early infection resolves on its own in most women. However, 25% will proceed to the next stage of the disease called "secondary" syphilis, which lasts 4-6 weeks. This secondary phase can include hair loss, a sore throat, white patches in the nose, mouth, and vagina, fever, headaches, and a skin rash. There can be lesions on the genitals that look like genital warts but are caused by spirochetes rather than the wart virus. These wart-like lesions, as well as the skin rash, are highly contagious. The rash can occur on the palms of the hands and the infection can be transmitted by casual contact. The third (‘tertiary") stage of the disease involves the brain and heart and is usually no longer contagious. At this point, however, the infection can cause extensive damage to the internal organs, such as the brain, and can lead to death.
    System, autonomic nervous: Part of the nervous system once thought functionally independent of the brain. The autonomic nervous system regulates key functions including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The autonomic nervous system has two divisions: (1) the sympathetic nervous system that accelerates the heart rate, constricts blood vessels, and raises blood pressure; and (2) the parasympathetic nervous system slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles.
    System, parasympathetic nervous: A part of nervous system that slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles. The parasympathetic nervous system together with the sympathetic nervous system (that accelerates the heart rate, constricts blood vessels, and raises blood pressure) constitute the autonomic nervous system.
    System, sympathetic nervous: A part of nervous system that accelerates the heart rate, constricts blood vessels, and raises blood pressure. The sympathetic nervous system together with the parasympathetic nervous system (that slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles) constitute the autonomic nervous system.
    Systemic-onset juvenile chronic arthritis: See: Systemic-onset juvenile rheumatoid arthritis (Still’s disease).
    Systemic-onset juvenile rheumatoid arthritis (Still’s disease): Also known as systemic-onset juvenile chronic arthritis. Still’s disease presents with systemic (bodywide) illness including high intermittent fever, a salmon-colored skin rash, swollen lymph glands, enlargement of the liver and spleen, and inflammation of the lungs (pleuritis) and around the heart (pericarditis). The arthritis may not be immediately apparent but, once apparent, it may persist after the systemic symptoms are gone.

    Systemic therapy: Treatment that reaches cells throughout the body by traveling through the bloodstream.
  • T: Commonly used abbreviation for temperature. For example, in a medical chart, you might see scrawled "BP90/60 T98.6 HR60/reg R15", which is short hand signifying that the blood pressure is 90/60 mm Hg, the temperature (T) is 98.6 degrees Fahrenheit, the heart rate (HR) is 60/min and regular, and the respirations ® 15/min. (This example would be entirely normal for an adult or older child).
    T-cell: A white blood cell made in the thymus gland, a lymphoid structure in the upper chest. (The T in T-cell stands for Thymus). The T-cells coordinate the immune system by secreting lymphokine hormones. There are 3 fundamentally different types of T cells : helper, killer, and suppressor. Each has many subdivisions. T-cells are also called T lymphocytes.
    T3: Triiodothyronine, a thyroid hormone. (The number 3 is usually in subscript.) Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.
    T4: Thyroxine, a thyroid hormone. (The number 4 is usually in subscript.) Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.
    T4 cell: Immune cells that are triggered by antibodies to seek and attack invading organisms. Cells called macrophanges summon T4 cells to the site of the infection and present a protruding antigen onto which the T4 cell locks, thus "recognizing" the invading substance. The T4 cell then reproduces and secretes its potent lymphokine hormones that stimulate B-cell production of antibodies; signal "natural killer" or cytotoxic (cell-killing) T-cells; and summon more macrophanges to the site of the infection. T4 cells are normally twice as common as T8 cells. If a person has AIDS, the proportion of T4 to T8 cells is often reversed. T4 cell are also called T-helper cells.
    T8 cell: A type of immune cells, T8 cells close down the immune response after it has destroyed invading organisms. T8 cells are sensitive to high concentrations of circulating lymphokine hormones and release their own lymphokines after an immune response has achieved its goal, signalling all other participants to cease their attack. Some memory B-cells remain to ward off a repeat attack by the invading organism. T8 cells are also called T-suppressor cells.
    T-cell lymphoma: A cancer of the immune system that appears in the skin; also called mycosis fungoides.
    T-helper cell: Immune cells that are triggered by antibodies to seek and attack invading organisms. Cells called macrophanges summon T-helper cells to the site of the infection and present a protruding antigen onto which the T-helper cell locks, thus "recognizing" the invading substance. The T4-helper cell then reproduces and secretes its potent lymphokine hormones that stimulate B-cell production of antibodies; signal "natural killer" or cytotoxic (cell-killing) T-cells; and summon more macrophanges to the site of the infection. T-helper cells are also called T4 cells and are normally twice as common as T8 cells. If a person has AIDS, the proportion of T4 to T8 cells is often reversed.
    T-lymphocyte: A white blood cell made in the thymus gland, a lymphoid structure in the upper chest. T lymphocytes are also called T-cells. (The T in T-cell stands for Thymus). These cells coordinate the immune system by secreting lymphokine hormones. There are 3 fundamentally different types of T lymphocytes : helper, killer, and suppressor.
    Tabes dorsalis: The slowly progressive degeneration of the spinal cord that occurs in the late (tertiary) phase of syphilis a decade or more after contracting the infection. Among the terrible features are lancinating lightning pain, ataxia (wobbliness), deterioration of the nerve to the eye (the optic nerve) leading to blindness, urinary incontinence, loss of the sense of position, and degeneration of the joints (Charcot’s joints). Tabes is the Latin word for decay. The term tabes dorsalis was devised in 1836 when the cause of the condition was thought to be wastage of the dorsal (posterior) columns of the spinal cord, well before it was recognized as part of late syphilis.
    Tabes spinalis: See Tabes dorsalis.
    Tabetic neurosyphilis: See Tabes dorsalis.
    Tablespoon: An old-fashionned but convenient household measure of capacity. A tablespoon holds about 5 cc. A tablespoon = 3 teaspoons.
    Tache noire: Black spot (in French), a small ulcer covered with a black crust at the site of a tick bite, characteristic of several tick-borne rickettsial diseases.
    Tachycardia: A rapid heart rate, usually defined as greater than 100 beats per minute.

    Tachycardia, paroxysmal atrial (PAT): Bouts of rapid, regular heart beating originating in the atrium (upper chamber of the heart). Often due to abnormalities in the AV node "relay station" that lead to rapid firing of electrical impulses from the atrium which bypass the AV node under certain conditions. These conditions include alcohol excess, stress, caffeine, overactive thyroid or excessive thyroid hormone intake, and certain drugs. PAT is an example of an arrhythmia where the abnormality is in the electrical system of the heart, while the heart muscle and valves may be normal.
    Tachycardia, sinus: Fast heartbeat (tachycardia) occurring because of rapid firing by the SA node, the natural pacemaker of the heart. Electrical signals initiated in the SA node are transmitted to the atria and the ventricles to stimulate heart muscle contractions heartbeats. Sinus tachycardia is usually a rapid contraction of a normal heart in response to a condition, drug, or disease. For examples, pain, fever, excessive thyroid hormone, exertion, excitement, low blood oxygen level (hypoxia), or stimulant drugs such as caffeine, cocaine, and amphetamines can cause tachycardia. However, in some cases, it can be a sign of heart failure or heart valve disease or other illness.
    Tachycardia, ventricular: An abnormal heart rhythm that is rapid, regular and originates from an area of the ventricle, the lower chamber of the heart. Ventricular tachycardias are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack.
    Tachypnea: Abnormally fast breathing.
    Tactile: Having to do with touch.
    Taenia: In medicine, it is a genus of large tapeworms. (In Latin, taenia meant a ribbon or tape.)
    Taenia saginata: The beef tapeworm. The most common of the big tapeworms that parasitizes people, contracted from infected raw or rare beef. Can grow to be 12-25 feet (3.6-7.5 m) long in the human intestine. Also known as the African tapeworm.
    Taenia solium: The pork tapeworm. Contracted from undercooked or measly pork (pork infected with the larval forms of the tapeworm). Can grow to be 3-6 feet (0.9-1.8 m) long in the human intestine. Also known as the armed tapeworm and the measly tapeworm.
    Tag, ear: Common minor anomaly, a rudimentary tag of ear tissue, often containing a core cartilage, usually located just in front of the ear (auricle). Therefore, also called preauricular tag. The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.
    Tag, preauricular: See Tag, ear.
    Talipes: Clubfoot. The Latin word talipes was compounded from talus (ankle) + pes (foot) since, with the common ("classic") type of clubfoot (talipes equinovarus), the foot is turned in sharply and the person seems to be walking on their ankle. Talipes equinovalgus: Malformation of the foot evident at birth in which the heel is elevated like a horse’s hoof (equino-) and the heel is turned outward (valgus).
    Talipes equinovarus: The common ("classic") form of clubfoot. Talipes is made up of the Latin talus (ankle) + pes (foot). Equino- indicates the heel is elevated (like a horse’s) and -varus indicates it is turned inward. With this type of clubfoot, the foot is turned in sharply and the person seems to be walking on their ankle.
    Tandem repeat sequences: Multiple copies of the same DNA base sequence on a chromosome; used as a marker in physical mapping of the chromosome.
    Tapazol: Trade name for methimazole, an antithyroid medication.
    Tapeworm: A worm that is flattened like a tape measure and functions as an intestinal parasite, unable to live freely on its own but able to do so within an animal’s gut.
    Tapeworm, African: See Taenia saginata.
    Tapeworm, armed: See Taenia solium.
    Tapeworm, beef: See Taenia saginata.
    Tapeworm, measly: See Taenia solium. The word measly does not imply that this is a puny tapeworm. Measly here refers to meat infested with the larval form of the pork tapeworm (t. solium). From eating the measly meat, you can acquire the tapeworm.
    Tapeworm, pork: See Taenia solium.
    Tarsal cyst: Also called a Meibomian cyst or a chalazian. A tarsal cyst is an inflammation of the oil gland of the eyelid.

    TAR syndrome: TAR stands for Thrombocytopenia (low blood platelets) and Aplasia (absence) of the Radius (the long bone on the thumb-side of the forearm), features characterizing this syndrome. There is phocomelia (flipper-limb) with the thumbs always present. The fibula (the smaller bone in the lower leg) is often absent. The risk of bleeding from too few platelets is high in early infancy but lessens with age. The condition is inherited in an autosomal recessive trait with one gene (on a non-sex chromosome) coming from each parent to the TAR child. Alternative names include thrombocytopenia-absent radius syndrome, radial aplasia-thrombocytopenia syndrome, and tetraphocomelia-thrombocytopenia syndrome.
    Tartar: Tartar is the hardened product of longstanding plaque accumulating minerals from the saliva and foods. Plaque is the soft accummulation of food debris and bacteria around teeth. These bacteria feed on left over food in the mouth to excrete toxins that irritate the gums and dissolve the bone. Plaque can be removed by proper brushing and flossing at home. Tartar can become as hard as a rock and then can require a dentist or dental hygienist with special tools to remove it. Dental plaque and tartar cause inflammation of the bone surrounding the teeth referred to as "periodontia."
    Td: Adult diphtheria and tetanus toxoids. See Td immunization.
    Td immunization: Td is the vaccine given to children over six and adults as a booster for immunity to diphtheria and tetanus.
    Teaspoon: Like a tablespoon, a teaspoon is an old-fashionned but convenient household measure. A teaspoon holds about 5 cc. Three teaspoons = a tablespoon.
    Technology, recombinant DNA: A series of procedures used to join together (recombine) DNA segments. A recombinant DNA molecule is constructed (recombined) from segments from 2 or more different DNA molecules. Under certain conditions, a recombinant DNA molecule can enter a cell and replicate there, autonomously (on its own) or after it has become integrated into a chromosome.
    Technology transfer: The process of converting scientific findings from research laboratories into useful products by the commercial sector.
    Telomere: The end of a chromosome. The ends of chromosomes are specialized structures that are involved in the replication and stability of DNA molecules.
    Temperature: The temperature is the specific degree of hotness or coldness of the body. It is usually measured with a thermometer.
    Temporal arteritis: Also called giant cell arteritis or cranial arteritis, this is a serious disease characterized by inflammation of the walls of the blood vessels (vasculitis). The vessels affected by inflammation are the arteries (hence the name "arteritis"). The age of affected patients is usually over 50 years of age. Giant cell arteritis can lead to blindness and/or stroke. It is detected by a biopsy of an artery. It is treated with high dose cortisone-related medications.
    Tempero-mandibular joint (TMJ): The TMJ hinges the lower jaw (mandible) to the skull.
    Tempero-mandibular joint (TMJ) syndrome: Disorder of the temporo-mandibular joint(s) causing pain usually in front of the ear(s). Pain in the TMJ can be due to trauma (such as a blow to the face), inflammatory or degenerative arthritis, or by the mandible being pushed back towards the ears whenever the patient chews or swallows. Sometimes, muscles around the TMJ used for chewing can go into spasm, causing head and neck pain and difficulty opening the mouth normally.
    Tendon: A tendon is the soft tissue by which muscle attaches to bone. When a tendon becomes inflamed, the condition is referred to as "tendinitis" or "tendonitis."
    Terminal ileitis: Crohn’s disease, a chronic inflammatory disease of the intestine involving only the end of the small intestine (the terminal ileum). Crohn’s disease affects primarilythe small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease often strikes persons in their teens or early twenties. It tends to be chronic, recurrent with periods of remission and exacerbation. In the early stages, It causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery.
    Test, Fisher’s exact: A statistical test of independence much used in medical research. It tests the independence of rows and columns in a 2 X 2 contingency table (with 2 horizontal rows crossing 2 vertical columns creating 4 places for data) based on the exact sampling distribution of the observed frequencies. Hence it is an "exact" test. Devised by the great British statistician R. A. Fisher (1890-1962).
    Test, glucose tolerance (GTT): After fasting, a specific amount (100 grams) of glucose is given by mouth, and the blood levels of this sugar are measured every hour. Normally, the blood glucose should return to normal within 2 to 2 ½ hours. The GTT is considered a classic test of carbohydrate metabolism. It is much used in the diagnosis of diabetes. The GTT depends on a number of factors including the ability of the intestine to absorb glucose, the power of the liver to take up and store glucose, the capacity of the pancreas to produce insulin, and the amount of "active" insulin.
    Test, skin, for allergy: Test done on the skin to identify the allergy substance (allergen) triggering the allergic reaction. A small amount of the suspected allergy substance is placed on the skin. The skin is then gently scratched through the small drop with a special sterile needle. If the skin reddens and, more importantly, swells, then allergy to that substance is probable.
    Testicles: The male sex glands. The testicles produce and store sperm and are the major source of testosterone.
    Testing, anonymous: Testing in which no name or other means is used to identify the person tested. There is total anonymity. For example, the State of Florida requires that each county have a site for anonymous HIV testing.
    Testosterone: A male sex hormone.

    Tetanus: An often fatal infectious disease due to a bacteria (Clostridium tetani) that usually enters the body through a puncture, cut or open wound. Tetanus leads to profound painful spasms of muscles, including"locking" of the jaw so the mouth cannot open (lockjaw), and death. Tetanus is the "T" in the DPT, DTaP, DT, and Td vaccines.
    Tetraphocomelia-thrombocytopenia syndrome: See TAR syndrome.
    Thalassemia: Not just one disease but rather a complex series of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of hemoglobin is made up of 4 polypeptide chains (usually 2 chains of one type and 2 chains of another type of chain). In thalassemia, there is a mutation (change) in one of the types of globin chains. Depending upon which globin chain is affected, the mutation typically leads to underproduction (or absence) of that globin chain, a deficiency of hemoglobin, and anemia.
    Thalassemia, beta: Also known as thalassemia major .The clinical picture of this important type of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley.. Other names for the disease are Cooley’s anemia and Mediterranean anemia. The name thalassemia was coined by the Nobel Prize winning pathologist George Whipple and the professor of pediatrics Wm Bradford at U. of Rochester because thalassa in Greek means the sea (like the Mediterrranean Sea) + -emia means in the blood so thalassemia means sea in the blood. Thalassemia is not just one disease. It is a complex contingent of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of normal adult hemoglobin is made up of 2 alpha and 2 beta polypeptide chains. In beta thalassemia, there is a mutation (change) in both beta globin chains leading to underproduction (or absence) of beta chains, underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin (for example, from Italy and Greece). Children with this disease inherit one gene for it from each parent. The parents are carriers (heterozygotes) with just one thalassemia gene, are said to have thalassemia minor, and are essentially normal. Their children affected with beta thalassemia seem entirely normal at birth because at birth we still have predominantly fetal hemoglobin which does not contain beta chains. The anemia surfaces in the first few months after birth and becomes progressively more severe leading to pallor and easy fatiguability, failure to thrive (grow), bouts of fever (due to infections) and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease.

    Thalassemia major: The dire disease also known as beta thalassemia. The clinical picture of this form of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley. Other names for the disease are Cooley’s anemia and Mediterranean anemia. The term thalassemia was coined by the Nobel Prize winning pathologist George Whipple and the professor of pediatrics William Bradford at U. of Rochester because thalassa in Greek means the sea (like the Mediterrranean Sea) + -emia means in the blood so thalassemia means sea in the blood. Thalassemia is not just one disease. It is a complex contingent of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of normal adult hemoglobin is made up of 2 alpha and 2 beta polypeptide chains. In beta thalassemia, there is a mutation (change) in both beta globin chains leading to underproduction (or absence) of beta chains, underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin (for example, from Italy and Greece). Children with this disease inherit one gene for it from each parent (and so are said to be homozygous for beta thalassemia). The parents are carriers (heterozygotes) with just one thalassemia gene, are said to have thalassemia minor, and are essentially normal. Their children affected with beta thalassemia seem entirely normal at birth (because at birth we still have predominantly fetal hemoglobin which does not contain beta chains) but the anemia emerges in the first few months of life and becomes progressively more severe leading to pallor and easy fatiguability, failure to thrive (grow), bouts of fever (due to infections) and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease.

    Thalassemia minor: Also called thalassemia trait, thalassemia minor is the carrier state for beta thalassemia. People who are carriers (heterozygotes) have just one thalassemia gene, are said to have thalassemia minor, and are essentially normal.
    Therapy, gene: Insertion of normal DNA directly into cells to correct a genetic defect. Gene therapy is the treatment of disease by replacing, altering, or supplementing a gene responsible for the disease. In gene therapy for cancer, for example, researchers are trying to bolster the body’s natural capacity to combat cancer and make the tumor more sensitive to other kinds of therapy. Gene therapy, still in its early stages, holds great promise for the treatment of many diseases.
    Third and fourth pharyngeal pouch syndrome: Also called the DiGeorge syndrome (DGS), this disorder is characterized by (1) low blood calcium levels (hypocalcemia) due to underdevelopment (hypoplasia) of the parathyroid glands which control calcium; (2) underdevelopment (hypoplasia) of the thymus, an organ behind the breastbone in which lymphocytes mature and multiply; and (3) defects of the heart involving the outflow tracts > from the heart. Most cases of DGS are due to a microdeletion in chromosome band 22q11.2. A small number of cases have defects in other chromosomes, notably 10p13. Named after the American pediatric endocrinologist Angelo DiGeorge. Another name for DGS is hypoplasia of the thymus and parathyroids.
    Thombi: Just the plural of thrombus. See: Thrombus.
    Thoracic: Pertaining to the chest.
    Thoracic duct: A vascular structure which recirculates lymph into the blood stream. It begins in the abdomen and tracks alongside the aorta and esophagus to eventually join with the left brachiocephalic vein.
    Thoracic outlet syndrome: Condition due to compromise of blood vessels or nerve fibers between the armpit (axilla) and base of the neck.
    Thoracotomy: An operation to open the chest.
    Thorax: The thorax is the area of the body located between the abdomen and the neck. It is also commonly referred to as the chest. Within the thorax are the lungs, heart and first section of the aorta.
    Thrombectomy: Procedure to remove a clot (a thrombus).
    Thrombin: A key clot promoter, thrombin is an enzyme that presides over the conversion of a substance called fibrinogen to fibrin, the right stuff for a clot.
    Thrombinogen: A coagulation factor needed for the normal clotting of blood. In the cascade of events leading to the final clot, thrombinogen precedes thrombin (and so is a precursor to thrombin). In fact, thrombinogen gives rise to thrombin, and also called prothrombin.
    Thrombocyte: A platelet. Crucial to normal blood clotting. Although platelets are sometimes classed as blood cells, they are not. They are fragments of a large cell called a megakaryocyte (literally, a large cell).
    Thrombocytopenia-absent radius syndrome: See TAR syndrome.
    Thoracentesis: Removal of fluid in the pleura through a needle.
    Thrombocytopenia-absent radius syndrome: See TAR syndrome.
    Thrombolytic agents: Medications such as plasminogen-activator (t-PA) and streptokinase that are effective in dissolving clots and re-opening arteries. Used, for example, in the treatment of heart attacks.
    Thrombophlebitis: Inflammation of a vein that occurs when a blood clot forms.
    Thrombotic disease due to protein C deficiency: Protein C is a protein in plasma that enters into the cascade of biochemical events leading to the formation of a clot. Deficiency of protein C results in thrombotic (clotting) disease and excess platelets with recurrent thrombophlebitis (inflammation of the vein that occurs when a clot forms). The clot can break loose and travel through the blood stream (thromboembolism) to the lungs causing a pulmonary embolism, brain causing a stroke (cerebrovascular accident), heart causing an early heart attack, skin causing what in the newborn is called neonatal purpura fulminans, the adrenal gland causing hemorrhage with abdominal pain, abnormally low blood pressure (hypotension), and salt loss. Protein C deficiency is due to possession of one gene (heterozygosity) in chromosome band 2q13-14. The possession of two such genes (homozygosity) is usually lethal.
    Thrombus: A clot in a blood vessel or within the heart.
    Thymine (T): One member of the base pair A-T (adenine-thymine) in DNA.
    Thymus: An organ in which lymphocytes mature and multiply. It lies behind the breastbone.

    Thymus and parathyroids, hypoplasia of: See Third and fourth pharyngeal pouch syndrome.
    Thyroglossal cyst: A thyroglossal cyst is a fluid-filled sac that is present at birth and located in the midline of the neck. A thyroglossal cyst is a result of incomplete closure of a segent of a tube-like structure (the thyroglossal duct) that is present, and normally closes, as the embryo develops. A thyroglossal cyst is also called a thyrolingual cyst.
    Thyroid: Gland located in the lower part of the neck, below the Adam’s apple, wrapped around the windpipe (trachea). The thyroid has the shape of a butterfly, since it is formed by two wings (lobes) which are attached by a middle part. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.
    Thyroid scan: A picture taken of the thyroid gland after radioactive iodine is taken by mouth.
    Thyroid hormones: Chemical substances made by the thyroid gland which is located in the front of the neck. The thyroid gland uses iodine to make thyroid hormones. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3).
    Thyroid stimulating hormone (TSH): A hormone produced by the pituitary gland (at the base of the brain) that promotes the growth of the thyroid gland (in the neck) and stimulates it. Normally, the rate of thyroid hormone production is controlled by the pituitary. When there are insufficient thyroid hormones in the body for normal functioning of the cells, the pituitary releases TSH. TSH in turn "stimulates" the thyroid gland to produce more thyroid hormones. In contrast, when there is excessive amount of thyroid hormones, the pituitary gland stops producing TSH. The TSH level then falls and thyroid hormone production is reduced. This mechanism maintains a relatively constant level of thyroid hormones circulating in the blood. This phenomenon is analogous to a thermostat used for temperature regulation in a room: when the temperature rises, the thermostat shuts the heater off and the room temperature falls back to normal. High levels of thyroid hormones cause the TSH level to fall, resulting in no further stimulation of the thyroid gland. In hyperthyroidism, there are continuously elevated levels of the thyroid hormones. TSH is also known as thyrotropin.
    Thyroid stimulating immunoglobulin (TSI): The TSI level is abnormally high in persons with hyperthyroidism (too much thyroid hormone) due to Graves’ disease.
    Thyroidectomy: Surgery to remove part or all of the thyroid gland. This might be done to remove a tumor or treat hyperthyroidism or goiter (enlarged thyroid gland). The goal of surgery in hyperthyroidism is to remove just enough thyroid gland so that a normal amount of thyroid hormone is produced. If too much thyroid is removed, the patient will produce too little thyroid hormone (hypothyroidism) and need treatment to return the thyroid status to normal (euthyroid). The complications of surgery can include vocal cord paralysis and accidental removal of the parathyroid glands (located behind the thyroid gland), resulting in low calcium levels (the parathyroid glands regulate calcium).
    Thyroiditis: Inflammation of the thyroid gland. The inflamed thyroid gland can releases an excess of thyroid hormones into the blood stream, resulting in a temporary hyperthyroid state. Once the thyroid gland is depleted of thyroid hormones, the patient commonly goes through a hypothyroid (low thyroid) phase. This phase can last 3-6 months until the thyroid gland fully recovers. Thyroiditis can be diagnosed by a thyroid scan (a picture taken of the thyroid gland after radioactive iodine is taken by mouth).
    Thyroiditis, autoimmune: A progressive disease of the thyroid gland with antibodies in the blood stream directed against the thyroid and infiltration of the gland by lymphoctes (a key type of white blood cells involved in the immune response). This immune response is against one’s own thyroid. (It is autoimmune.) Predominantly affects women. Can be familial. Also called Hashimoto’s disease or Hashimoto’s thyroiditis.

    Thyroiditis, Hashimoto’s: Autoimmune thyroiditis. A progressive disease of the thyroid gland with antibodies in the blood stream directed against the thyroid and infiltration of the gland by lymphoctes (a key type of white blood cells involved in the immune response). This immune response is against one’s own thyroid. (It is autoimmune.) Predominantly affects women. Can be familial. Also called Hashimoto’s disease.
    Thyroiditis, postpartum: Inflammation of the thyroid gland after pregnancy.
    Thyroiditis, subacute: Inflammation of the thyroid gland after a viral illness.
    Thyrolingual cyst: A thyrolingual cyst is a fluid-filled sac that is present at birth and located in the midline of the neck. A thyrolingual cyst is a result of incomplete closure of a segent of a tube-like structure (the thyrolingual duct) that is present, and normally closes, as the embryo develops. A thyrolingual cyst is also called a thyroglossal cyst.
    Thyrotropin: A hormone produced by the pituitary gland (at the base of the brain) that promotes the growth of the thyroid gland (in the neck) and stimulates it. The suffix -tropin indicates "an affinity for". Thyrotropin has an affinity for the thyroid. Thyrotropin is known also as thyroid stimulating hormone (TSH).
    Thyroxine: A chemical substance made by the thyroid gland The thyroid gland uses iodine to make thyroid hormones. Thyroxine (T4), one of the most important thypoid hormones, has four iodine molecules attached to its molecular structure. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.
    Tick-borne rickettsioses of the eastern hemisphere: Thare are 3 known diseases caused by infection with rickettsial agents. They are North Asian tick-borne rickettsiosis, Queensland tick typhus, and African tick typhus (fièvre boutonneuse).
    Tick-borne rickettsiosis, north Asian: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.
    Tick fever: See Rocky Mountain spotted fever.
    Tick typhus: See Typhus, tick.
    Tick typhus, African: See Typhus, African tick.
    Tick typhus, Queensland: See Typhus, Queensland tick.
    Tinea unguium: The most common fungus infection of the nails (onychomycosis). Onychomycosis makes the nails look white and opaque, thickened, and brittle. Older women (perhaps because estrogen deficiency may increase the risk of infection). and men and women with diabetes or disease of the small blood vessels (peripheral vacscular disease) are at increased risk. Artificial nails (acrylic or "wraps") increase the risk because when an artificial nail is applied, the nail surface is usually abraded with an emery board damaging it, emery boards can carry infection, and. water can collect under the nail creating a moist, warm environment for fungal growth. Alternative names include ringworm of the nails and dermatophytic onychomycosis.
    Tinnitus: Ringing in the ears. Tinnitus has many causes including medications (such as aspirin, and other antiinflammatory drugs), aging, and ear trauma.
    Tissue: A group or layer of cells that perform specific functions.
    TMA: See Trimethylaminuria
    TMJ: Tempero-mandibular joint, the joint that hinges the lower jaw (mandible) to the skull.
    TMJ syndrome: Disorder of the temporo-mandibular joint(s) causing pain usually in front of the ear(s).
    Tonsillectomy: The surgical removal of both tonsils.
    Tonsillitis: Inflammation of the of a tonsil, typically as a result of infection by either a virus or bacteria.
    Tonsils: Small masses of lymphoid tissue at the back of the throat, on either side of the throat.

    Tooth, cracked, syndrome: A toothache caused by a broken tooth (tooth fracture) without associated cavity or advanced gum disease. Biting on the area of tooth fracture can cause severe sharp pains. These fractures are usually due to chewing or biting hard objects such as hard candies, pencils, nuts, etc. Sometimes, the fracture can be seen by painting a special dye on the cracked tooth. Treatment usually is to protect the tooth with a crown. However, if placing a crown does not relieve pain symptoms, a root canal procedure may be necessary.
    Tooth root sensitivities: Oversensitivity of exposed roots of teeth to cold, hot, and sour foods because those roots are no longer protected by healthy gum and bone. Chronic gum disease contributes to toothache due to root sensitivities. The roots are the lower 2/3 of the teeth that are normally buried in bone. The bacterial toxins dissolve the bone around the roots and cause the gum and the bone to recede, exposing the roots. The sensitivities may be so severe that the person avoids any cold or sour foods.
    Topical chemotherapy: Treatment with anticancer drugs in a lotion or cream.
    Tophaceous gout: Nodular masses of uric acid crystals (tophi) are deposited in different soft tissue areas of the body. Even though tophi are most commonly found as hard nodules around the fingers, at the tips of the elbows, and around the big toe, tophi nodules can appear anywhere in the body. They have been reported in unexpected areas such as in the ears, vocal cords, or around the spinal cord! Tophaceous gout is always a result of chronic gout.
    Tophi: The plural of tophus.
    Tophus: A nodular mass of uric acid crystals. Tophi are characteristically deposited in different soft tissue areas of the body in gout. The word tophus comes via Latin from the Greek tophos meaning a porous volcanic stone. In chronic (tophaceous) gout, nodular masses of uric acid crystals (tophi) deposit in different soft tissue areas of the body. Even though tophi are most commonly found as hard nodules around the fingers, at the tips of the elbows, and around the big toe, tophi nodules can appear anywhere in the body. They have been reported in unexpected areas such as in the ears, vocal cords, or around the spinal cord!
    Torsion dystonia: A form of dystonia known as early-onset torsion dystonia (also called idiopathic or generalized torsion dystonia) that begins in childhood around the age of 12. Symptoms typically start in one part of the body, usually in an arm or leg, and eventually spread to the rest of the body within about 5 years. Early-onset torsion dystonia is not fatal, but it can be severely debilitating. Most children with the disorder are unable to perform the simplest of motor tasks and are confined to a wheelchair by the time they reach adulthood.
    Torticollis, spasmodic: Spasmodic torticollis, or torticollis, is the most common of the focal dystonias. In torticollis, the muscles in the neck that control the position of the head are affected, causing the head to twist and turn to one side. In addition, the head may be pulled forward or backward. Called wry neck.
    Total hysterectomy: Complete surgical removal of the uterus and cervix. Also called a complete hysterectomy.
    Toxic shock: See Toxic shock syndrome.
    Toxic multinodular goiter: Condition in which the thyroid gland contains multiple lumps (nodules) that are overactive, produce excess thyroid hormones and thereby cause hyperthyroidism. This condition is also known as Parry’s disease or Plummer’s disease.
    Toxic shock syndrome: A grave condition occurring predominantly in menstruating women using tampons, toxic shock is characterized by a highly toxic state (with sudden high fever, vomiting, diarrhea, muscle aching) followed by low blood pressure (hypotension) which can lead to shock (and death). There may be a rash resembling sunburn with peeling of skin. The Channing Laboratory in Boston under Dr. Edw. Kass discovered that toxic shock was due to a toxin produced by Staph (Staphylococcus) aureus bacteria growing under conditions with little or no oxygen. The syndrome occurs rarely in women not using tampons and in men.
    Toxins: Poisons produced by certain animals, plants, or bacteria.

    Trachea: The trachea is a tube-like portion of the breathing or "respiratory" tract that connects the "voice box" (larynx) with the bronchial parts of the lungs. It is also called the "windpipe."
    Tracheoesophageal puncture: A small opening made by a surgeon between the esophagus and the trachea. A valve keeps food out of the trachea but lets air into the esophagus for esophageal speech.
    Tracheostomy: Surgery to create an opening (stoma) into the windpipe. The opening itself may also be called a tracheostomy.
    Tracheostomy button: A 1/2- to 1 1/2-inch-long plastic tube placed in the stoma to keep it open.
    Tracheostomy tube: A 2- to 3-inch metal or plastic tube that keeps the stoma and trachea open. Also called a trach ("trake") tube.
    Transcription: Making an RNA copy from a sequence of DNA (a gene). Transcription is the first step in gene expression.
    Transfusion: The transfer of blood or blood products from one person to another.
    Transitional cell carcinoma: Cancer that develops in the lining of the renal pelvis. This type of cancer also occurs in the ureter and the bladder.
    Transfer RNA (tRNA): A class of RNA that has triplet nucleotide sequence complementary to the triplet nucleotide coding sequences of messenger RNA (mRNA). The role of tRNAs is to bond with amino acids and transfer them to the ribosomes, where proteins are assembled according to the genetic code carried by mRNA
    Translation: To go from RNA to protein, translation is needed. Translation is the process by which the genetic code carried by messenger RNA (mRNA) directs the production of proteins from amino acids.
    Transsexual: A person who desires or has achieved transsexualism (by having a sex change operation, etc.). A transsexual is different from a transvestite who is a person who masquerades by dressing in the clothing of the opposite sex (cross-dressing). See: Transsexualism.
    Transsexualism: Consistently strong desire to change ones anatomic sex and belong to the opposite sex, to change gender and do so by all available means (including surgery, hormonal treatment, dress, and life style). "Trans-" is related to the Latin verb "transire", meaning "to pass or cross over, or pass beyond." In transsexualism, one crosses over or passes beyond ones sex to the opposite sex. Transsexualism is thus distinct from mere cross-dressing which is termed transvestism (from the Latin "vestitus" meaning "clothed"). (A publicized instance of transsexualism involved the ophthalmologist Dr. Richard Raskind who became the professional tennis player, Renée Richards, on the ladies’ tour.)
    Transurethral resection: Surgery performed with a special instrument inserted through the urethra. Also called TUR.
    Transvaginal ultrasound: Sound waves sent out by a probe inserted in the vagina. The waves bounce off the ovaries, and a computer uses the echoes to create a picture called a sonogram. Also called TVS.
    Transvestism: Dressing in the clothing of the opposite sex. Also called cross-dressing. The prefix "trans-" relates to the Latin verb "transire", meaning "to pass or cross over, or pass beyond" while the "-vestism" stems from "vestitus" meaning "clothed." In centuries past, the Catholic Church forbade women from acting in the theater. Therefore, stage roles for females had to be played by males who dressed as females—male transvestism, at least for the duration of the performance.
    Transvestite: A person who dresses in the clothing of the opposite sex, i.e., a person who cross-dresses.
    Treadmill, exercise: A continuous EKG recording of the heart as the patient performs increasing levels of exercise. In addition to detecting abnormal heart rhythms (arrhythmias), the exercise treadmill is a screening test for the presence of narrowed coronary arteries that can limit the supply of oxygenated blood to the heart muscle during exercise.
    Tremor: A tremor is an abnormal repetitive shaking movement of the body. Tremors have many causes and can be inherited, related to illnesses (such as thyroid disease), fever, hypothermia, drugs or fear.
    Trench fever: A louse-borne disease first recognized in the trenches of World War I, again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Also called Wolhynia fever, shin bone fever, quintan fever, five-day fever, Meuse fever, His’ disease, His-Werner disease, Werner-His disease.
    Treponema pallidum: The cause of syphilis, this is a microscopic bacterial organism called a spirochete, a worm-like spiral-shaped organism that wiggles vigorously when viewed under a microscope. Treponema pallidum was discovered in 1905 by the German bacteriologist Fritz Schaudinn (1871-1906) who named it, putting together the Greek trepo (I turn) and nema (thread) with the Latin pallida (pale) to make a pale turning thread.
    Tricuspid valve: The heart valve between the right atrium and right ventricle. Normally allows blood to flow only from the atrium into the ventricle.
    Triiodothyronine: A hormone made by the thyroid gland. The thyroid gland uses iodine to make thyroid hormones. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body. Triiodothyronine (T3) has three iodine molecules attached to its molecular structure. Iodine is found in seafood, bread, seaweed, and ordinary table salt.
    Trimethylaminuria (TMA): An inborn error of metabolism associated with an offensive body odor, the smell of rotting fish, due to the excessive excretion of TMA in urine, sweat, and breath. Persons with TMA may experience tachycardia (fast heart rate) and severe hypertension (high blood pressure) after eating cheese (which contains tyramine) and after using nasal sprays containing epinephrine. TMA is caused by a mutation (change) in the gene for an enzyme, flavin-containing monooxygenase-3 (FMO3) encoded by a gene on chromosome #1. The FMO3 enzyme metabolizes tyramine (which is in cheese). The syndrome is associated with various psychosocial reactions, including social isolation, clinical depression and attempted suicide.
    Trisomy 13 syndrome: Condition with three rather than the normal two chromosomes #13. Children born with this syndrome have multiple malformations and mental retardation due to the extra chromosome #13. The congenital malformations (birth defects) commonly include scalp defects, hemangiomas (blood vessel malformations) of the face and nape of the neck, cleft lip and palate, malformations of the heart and abdominal organs, and flexed fingers with extra digits. The mental retardation is profound. The IQ is untestably low. The majority of trisomy 13 babies die soon after birth or in infancy. The condition is also called Patau syndrome after the late geneticist Klaus Patau (at the University of Wisconsin) who discovered the extra chromosome in 1960.
    Trisomy 18 syndrome: There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is profound with the IQ too low to even test. Nineteen out of 20 (95%) of these children die before their first birthday. The condition is also called Edwards syndrome in honor of the British physician and geneticist John Edwards who discovered the extra chromosome in 1960.
    Trisomy 21 syndrome: A common chromosome disorder due to an extra chromosome number 21 (trisomy 21). The syndrome causes mental retardation, a characteristic face, and multiple malformations. It is associated with a major risk for heart problems, a lesser risk of duodenal atresia (part of the intestines not developed), and a minor but still significant risk of acute leukemia. Trisome 21 syndr0ome is also commonly called Down syndrome after the 19th century English doctor Langdon Down who was curiously enough not the first person to describe the condition, added little to knowledge and, in great error, attributed the condition to a "reversion" to the mongoloid race. The disorder was also once called mongolism, a term now considered slang.
    tRNA: Transfer RNA.
    Tropical typhus: See Typhus, scrub.
    TSH: Stands for Thyroid Stimulating Hormone. Also known as thyrotropin.
    TSI: Stands for Thyroid Stimulating Immunoglobulin. The TSI level is abnormally high in persons with hyperthyroidism (too much thyroid hormone) due to Graves’ disease. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.
    Tsutsugamushi disease: See Typhus, scrub.
    T-suppressor cell: A type of immune cells, also called T8 cells, these cells close down the immune response after it has destroyed invading organisms. T8 cells are sensitive to high concentrations of circulating lymphokine hormones and release their own lymphokines after an immune response has achieved its goal, signalling all other participants to cease their attack. Some memory B-cells remain to ward off a repeat attack by the invading organism.
    Tubes, Fallopian: The Fallopian tubes normally transport the egg of the female from the egg sac, or ovary, to the womb, or uterus. Normal tubes have small hair like projections on the lining cells called cilia. These cilia are important to movement of the egg through the fallopian tube and into the uterus. If the tubal cilia are damaged by infection, the egg may not get ‘pushed along’ normally and can settle in the tube. Likewise, if infection causes partial blockage of the tube with scar tissue, this can also act to prevent the egg from getting to the uterus. Any process that narrows the tube and thus decrease the caliber of the passage way can increase the chance of an ectopic pregnancy. Examples of these would be endometriosis, tumors, or scar tissue in the pelvis (pelvic adhesions) that cause twisting or chinking of the tube.

    Tumor: An abnormal mass of tissue. A classic sign of inflammation. Tumors can be benign or malignant.
    Tumor debulking: Surgically removing as much of the tumor as possible.
    Tumor markers: Substances found in abnormal amounts in the blood, in other body fluids, or in tumor tissue of some patients with certain types of cancer. Examples are alphafetoprotein (AFP), human chorionic gonadotropin, and lactate dehydrogenase (LDH).
    Tumor registry: Recorded information about the status of patients with tumors. Although a registry was originally the place (like Registry House in Edinburgh) where information was collected (in registers), the word registry has also come to mean the collection itself. A tumor registry is organized so the data can be analyzed. For example, analysis of data in a tumor registry maintained at a hospital may show a rise in lung cancer among women.
    Tunica albuginea: The whitish membrane within the penis that surrounds the spongy chambers (corpora cavernosa) in the penis and which helps to trap the blood in the corpora cavernosa, thereby sustaining erection of the penis. The term comes straight from the Latin tunica (covering or coat) + albuginea (white) = a covering that is white, like the white (albumen) of an egg.
    Tunica albuginea: Literally, the white coat. In anatomy, a dense white fibrous covering.
    Tunica albuginea of the testis: The layer of dense whitish inelastic tissue that surrounds the testis.
    Turner-Kieser syndrome: See nail-patella syndrome (Turner in 1933 described two families with the disease. The name Turner is more closely associated with the XO syndrome).
    Tympanic membrane: Just the ear drum.
    Tympanoplasty: A surgical operation to correct damage to the middle ear and restore the integrity of the ear drum. Tympano- comes from the Greek tympanon meaning drum.
    Tympanum: The anatomic name for the cavity of the middle ear which is separated from the outer ear by the ear drum.
    Tympany: A hollow drum-like sound produced when a gas-containing cavity is tapped sharply. Tympany is heard if the chest contains free air(pneumothorax) or the abdomen is distended with gas.
    Typist’s cramp: A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs during handwriting. Similar focal dystonias have also been called writer’s cramp, pianist’s cramp, musician’s cramp, and golfer’s cramp.
    Typhus, African tick: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (tache noire) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash. Also called fièvre boutonneuse.
    Typhus, classic: See Typhus, epidemic.
    Typhus, endemic: See Typhus, murine.
    Typhus, epidemic: A severe acute disease with prolonged high fever up to 40° C (104° F), intractable headache, and a pink-to-red raised rash. The cause is a microorganism called Rickettsia prowazekii. It is found worldwide and is transmitted by lice. The lice become infected on typhus patients and transmit illness to other people. The mortality increases with age and over half of untreated persons age 50 or more die. Also called European, classic, or louse-borne typhus and jail fever.
    Typhus, European: See Typhus, epidemic.
    Typhus, louse-borne: See Typhus, epidemic.
    Typhus, mite-borne: See Typhus, scrub.
    Typhus, murine: An acute infectious disease with fever, headache, and rash, all quite similar to, but milder than, epidemic typhus, caused by a related microoganism, Rickettsia typhi (mooseri), transmitted to humans by rat fleas (Xenopsylla cheopis). The animal reservoir includes rats, mice and other rodents. Murine typhus occurs sporadically worldwide but is more prevalent in congested rat-infested urban areas. Also known as endemic typhus, rat-flea typhus, and urban typhus of Malaya.
    Typhus, Queensland tick: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.
    Typhus, scrub: A mite-borne infectious disease caused by a microorganism, Rickettsia tsutsugamushi, characteristically with fever, headache, a raised (macular) rash, swollen glands (lymphadenopathy) and a dark crusted ulcer (called an eschar or tache noire) at the site of the chigger (mite larva) bite. This disease occurs in the area bounded by Japan, India, and Australia. Known also as Tsutsugamushi disease, mite-borne typhus, and tropical typhus.
    Typhus, rat-flea: See Typhus, murine.
    Typhus, tick: Rocky Mountain spotted fever (RMSF), an acute febrile (feverish) disease initially recognized in the Rocky Mountain states, caused by Rickettsia rickettsii transmitted by hard-shelled (ixodid) ticks. Occurs only in the Western Hemisphere. Anyone frequenting tick-infested areas is at risk for RMSF. Onset of symptoms is abrupt with headache, high fever, chills, muscle pain. and then a rash .The rickettsiae grow within damaged cells lining blood vessels which may become blocked by clots. Blood vessel inflammation (vasculitis) is widespread Early recognition of RMSF and prompt antibiotic treatment is important in reducing mortality. Also called spotted fever and tick fever.
    Typhus, tropical: See Typhus, scrub.

    Typhus, urban. of Malaysia: See Typhus, murine.
  • UBT: Urea breath test.
    Ulcer, duodenal: An ulcer (a hole in the lining) of the duodenum (the first portion of the small intestine). Ulcer formation is related to H. pyloridus bacteria in the stomach, anti-inflammatory medications, and smoking cigarettes. Ulcer pain may not correlate with the presence or severity of ulceration. Diagnosis is made with barium x-ray or endoscopy. Complications of ulcers include bleeding and perforation. Treatment involves antibiotics to eradicate H. pyloridus, eliminating risk factors, and preventing complications.
    Ulcer, esophageal: A hole in the lining of the esophagus (tube-like organ leading from the throat to the stomach) corroded by the acidic digestive juices secreted by the stomach cells. Ulcer formation is related to H. pyloridus bacteria in the stomach, anti-inflammatory medications, and smoking cigarettes. Ulcer pain may not correlate with the presence or severity of ulceration. Diagnosis is made with barium x-ray or endoscopy. Complications of ulcers include bleeding and perforation. Treatment involves antibiotics to eradicate H. pyloridus, eliminating risk factors, and preventing complications.
    Ulcer, gastric: A hole in the lining of the stomach corroded by the acidic digestive juices which are secreted by the stomach cells. Ulcer formation is related to H. pyloridus bacteria in the stomach, anti-inflammatory medications, and smoking cigarettes. Ulcer pain may not correlate with the presence or severity of ulceration. Diagnosis is made with barium x-ray or endoscopy. Complications of ulcers include bleeding, perforation, and blockage of the stomach (gastric obstruction).
    Ulcer, peptic: A peptic ulcer is a hole in the lining of the stomach, duodenum, or esophagus. A peptic ulcer of the stomach is called a gastric ulcer, an ulcer of the duodenum is a duodenal ulcer, and a peptic ulcer of the esophagus is an esophageal ulcer. A peptic ulcer occurs when the lining of these organs is corroded by the acidic digestive juices which are secreted by the stomach cells. Peptic ulcer disease is common, affecting millions of Americans yearly. The medical cost of treating peptic ulcer and its complications runs in the billions of dollars annually in the U.S. Recent medical advances have increased our understanding of ulcer formation. Improved and expanded treatment options are now available.
    Ultrasound/Ultrasonography: A test in which high-frequency sound waves (ultrasound) are bounced off tissues and the echoes are converted into a picture (sonogram).
    Ultraviolet radiation: Invisible rays that are part of the energy that comes from the sun. Ultraviolet radiation can burn the skin and cause skin cancer. It is made up of two types of rays, UVA and UVB. UVB rays are more likely than UVA rays to cause sunburn, but UVA rays pass further into the skin. Scientists have long thought that UVB radiation can cause melamona and other types of skin cancer. They now think that UVA radiation also may add to skin damage that can lead to cancer. For this reason, skin specialists recommend that people use sunscreens that block both kinds of radiation.
    Umbilicus: The navel or belly button.
    Unicornuate: Having one horn or being shaped-shaped. The uterus is normally unicornuate.
    Unique identifier reporting: In public health, a system that uses information such as the person’s birth date and part of their identification number (in the U.S., the social security number) to create a unique code that is reported instead of a name. It is an alternative to named reporting that provides some of the surveillance benefits of reporting by name, such as the elimination of duplicate reports, while reducing privacy concerns by avoiding use of a person’s name. For example, HIV testing in Maryland and Texas is done with unique identifier reporting.
    Upper GI series: A series of x-rays of the esophagus, stomach, and small intestine (upper gastrointestinal, or GI, tract) that are taken after the patient drinks a barium solution. (Barium is a white, chalky substance that outlines the organs on the x-ray.)
    Urban typhus of Malayia: Murine typhus, an acute infectious disease with fever, headache, and rash, all quite similar to, but milder than, epidemic typhus, caused by a related microoganism, Rickettsia typhi (mooseri), transmitted to humans by rat fleas (Xenopsylla cheopis). The animal reservoir includes rats, mice and other rodents. Murine typhus occurs sporadically worldwide but is more prevalent in congested rat-infested urban areas. Also known as endemic typhus, andrat-flea typhus.
    Urea: A substance containing nitrogen that is normally cleared from the blood into the urine by the kidney. Diseases that compromise the function of the kidney often lead to increased blood levels of urea, measured by the blood urea nitrogen (BUN) test.
    Urea breath test (UBT): A test for the presence of the bacteria Helicobacter pylori that causes inflammation and ulcers in the stomach. The breath test is based on the ability of H. pylori to break down urea. Ten minutes after swallowing a capsule containing urea with labeled carbon, a breath sample is collected to detect labeled carbon in the exhaled breath. A positive test indicates active infection. The test turns negative after eradication of the bacteria from the stomach with antibiotics.
    Urethra: Transport tube leading from the bladder to discharge urine outside the body. In males the urethra travels through the penis.
    Urethritis: Inflammation of the urethra. The urethra is the transport tube leading from the bladder to discharge urine outside the body.
    Ureters: The tubes that carry urine from each kidney to the bladder.
    Uric acid: A breakdown product of purines that are part of many foods. In gout, there are frequently, but not always, elevated levels of uric acid in the blood (hyperuricemia). However, only a small portion of those with hyperuricemia will develop gout.
    Urinalysis: A test that determines the content of the urine.
    Urinary: Having to do with the kidneys, ureters, and bladder. The urinary system represents the functional and anatomic aspects of the kidneys, ureters, and bladder.
    Urinary tract: The organs of the body that produce and discharge urine. These include the kidneys, ureters, bladder, and urethra.
    Urinary tract infection (UTI): Infection of the kidney, ureter, bladder, or urethra. Not everyone with a UTI has symptoms. Common symptoms include a frequent urge to urinate and a painful, burning when urinating. More females than males have UTIs. Underlying conditions that impair the normal urinary flow can lead to complicated UTIs.
    Urine: Liquid waste.
    Urologist: A doctor who specializes in diseases of the urinary organs in females and the urinary and sex organs in males.
    Uterine tubes: See Fallopian tubes.
    Uterus: A small, pear-shaped muscular organ in the pelvis of females where the unborn child develops until birth. Also called the womb.
    Urticaria: Hives. Raised, itching areas of skin, often a sign of an allergic reaction. Also called "welts" or "nettle rash."
    UTI: Urinary tract infection. (Not to be confused with URI: upper respiratory infection).

    Uvula: The prominent anatomic structure dangling downward visibly at the back of the mouth (pharynx).
  • Vaccines: Vaccines are microbial preparations of killed or modified microorganisms which can stimulate an immune response in the body in order to prevent future infection with similar microorganism. The smallpox vaccine has totally eliminated the smallpox disease from our planet.
    Vaccination: Injection of a killed microbe in order to stimulate the immune system against the microbe, thereby preventing disease. Vaccinations, or immunizations, work by stimulating the immune system, the natural disease-fighting system of the body. The healthy immune system is able to recognize invading bacteria and viruses and produce substances (antibodies) to destroy or disable them. Immunizations prepare the immune system to ward off a disease. To immunize against viral diseases, the virus used in the vaccine has been weakened or killed. To only immunize against bacterial diseases, it is generally possible to use a small portion of the dead bacteria to stimulate the formation of antibodies against the whole bacteria. In addition to the initial immunization process, it has been found that the effectiveness of immunizations can be improved by periodic repeat injections or "boosters." Also see Vaccines (in the plural) and Vaccine of a specific type (such Vaccine, Polio).
    Vaccination, anthrax: A series of six shots over six months and booster shots annually, the anthrax vaccine now in use in the USA was first developed in the 1950s and approved by the Food and Drug Administration for general use in 1970. It is produced by the Michigan Biologic Products Institute of Michigan’s Department of Health and is given routinely to veterinarians and others working with livestock. In December, 1997 it was announced that all US military would receive the vaccine, as do the military in the UK and Russia, the reason being concern that anthrax might be used in biologic warfare.
    Vaccination, children’s: In the United States, it is recommended that all children receive vaccination against: - Hepatitis B - Diphtheria, tetanus, pertussis - Haemophilus influenzae type B (HIB)
    - Poliovirus
    - Measles, mumps, rubella
    - Varicella zoster virus (chickenpox). Every child in the U.S. should have these vaccinations except when there are special circumstances and the child’s doctor advises specifically against a vaccination..
    Vaccination, chickenpox: This vaccine prevents the common disease known as chickenpox (varicella zoster). While chickenpox is often considered a trivial illness, it can cause significant lost time on the job and in school and have serious complications including ear infections, pneumonia, and infection of the rash with bacteria, inflammation of the brain (encephalitis) leading to difficulty with balance and coordination (cerebellar ataxia), damaged nerves (palsies), and Reye’s syndrome, a potentially fatal complication. The vaccination requires only one shot given at about a year of age. If an older person has not had chickenpox, the shot may be given at any time. There have been few significant reactions to the chickenpox vaccine. All children, except those with a compromised immune system, should have the vaccination.
    Vaccination, DTaP: Like DPT, DTaP protects from diphtheria, pertussis (whooping cough) and tetanus. DTaP is the same as DTP, except that it contains only acellular pertussis vaccine which is thought to cause fewer of the minor reactions associated with immunization and is also probably less likely to cause the more severe reactions occasionally seen following pertussis vaccination. DTaP is currently recommended only for the shots given at 18 months and 4-6 years of age.
    Vaccination, DT: DT (diphtheria and tetanus) vaccine does not protect from pertussis and is usually reserved for individuals who have had a significant adverse reaction to a DPT shot or who have a personal or family history of a seizure disorder or brain disease
    Vaccination, German measles: See Vaccination, MMR.
    Vaccination, Haemophilus influenzae type B: See Vaccination, HIB.

    Vaccination, hepatitis A: When immediate protection against hepatitis A (infectious hepatitis) is needed, immunoglobulins are used. Protection is effective only if given within 2 weeks of exposure and lasts but 2-4 months. Immunoglobulins can be used to protect household contacts of someone with acute viral hepatitis and travelers to regions with poor sanitation and high hepatitis A rates, when the traveler has to depart sooner than the vaccines can take effect (about 2 weeks). Travelers can receive the immunoglobulin and vaccine simultaneously and be protected immediately and for longer term. When immediate protection is not needed, hepatitis A vaccines are considered for individuals in high-risk settings, including frequent world travelers, sexually active individuals with multiple partners, homosexual men, individuals using illicit drugs, employees of daycare centers, and certain health care workers, and sewage workers. Two hepatitis A vaccines called HAVRIX and VAQTA are commercially available in the U.S. Both are highly effective and provide protection even after only one dose. Two doses are recommended for adults and 3 doses for children (under 18 years of age) to provide prolonged protection.
    Vaccination, hepatitis B: Hepatits B (hep B) vaccine gives prolonged protection, but 3 shots over a half year are usually required. In the U.S., all infants receive hep B vaccine. Two vaccines (ENGERIX-B, and RECOMBIVAX-HB) are available in the US. The first dose of hep B vaccine is frequently given while the newborn is in the hospital or at the first doctor visit following birth. The second dose is given about 30 days after the initial dose. A booster dose is performed approximately six months later. Babies born to mothers testing positive for hep B receive, in addition, HBIG (hep B immune globulin) for prompt protection. Older children (11-12 years) are advised to receive a hep B booster as are adults in high-risk situations including healthcare workers, dentists, intimate and household contacts of patients with chronic hep B infection, male homosexuals, individuals with multiple sexual partners, dialysis patients, IV drug users, and recipients of repeated transfusions. Health care workers accidentally exposed to materials infected with hep B (such as needle sticks), and individuals with known sexual contact with hep B patients are available in the U.S. Both are highly effective and provide protection even after only one dose. Two doses are recommended for adults and 3 doses for children (under 18 years of age) to provide prolonged protection. Vaccination, hepatitis B: Hepatits B (hep B) vaccine gives prolonged protection, but 3 shots over a half year are usually required. In the U.S., all infants receive hep B vaccine. Two vaccines (ENGERIX-B, and RECOMBIVAX-HB) are available in the US. The first dose of hep B vaccine is frequently given while the newborn is in the hospital or at the first doctor visit following birth. The second dose is given about 30 days after the initial dose. A booster dose is performed approximately six months later. Babies born to mothers testing positive for hep B receive, in addition, HBIG (hep B immune globulin) for prompt protection. Older children (11-12 years) are advised to receive a hep B booster as are adults in high-risk situations including healthcare workers, dentists, intimate and household contacts of patients with chronic hep B infection, male homosexuals, individuals with multiple sexual partners, dialysis patients, IV drug users, and recipients of repeated transfusions. Health care workers accidentally exposed to materials infected with hep B (such as needle sticks), and individuals with known sexual contact with hep B patients are usually given both HBIG and vaccine to provide immediate and long term protection.
    Vaccination, H. flu: See Vaccination, HIB.
    Vaccination, HIB: This vaccine is to prevent disease caused by the Haemophilus influenzae type B (HIB) bacteria. The H. influenzae (H. flu) bacteria can cause a range of serious diseases including meningitis with potential brain damage and epiglottitis with airway obstruction poisoning. The HIB vaccine is usually given at 2, 4 and 6 months of age. A final booster is given at 12-15 months of age. HIB vaccine rarely causes severe reactions.
    Vaccination, infectious hepatitis: See Vaccination, hepatitis A.
    Vaccination, measles: See Vaccination, MMR. Vaccination, MMR: The standard vaccine given to prevent measles, mumps and rubella (German measles). The MMR vaccine is now given in two dosages. The first should be given at12-15 months of age. The second vaccination hould be given at 4-6 years (or, alternatively, 11-12 years) of age. Most colleges require proof of a second measles or MMR vaccination prior to entrance. Most children should receive MMR vaccinations. Exceptions may include children born with an inability to fight off infection, some children with cancer, on treatment with radiation or drugs for cancer, on long term steroids (cortisone). People with severe allergic reactions to eggs or the drug neomycin should probably avoid the MMR vaccine. Pregnant women should wait until after delivery before being immunized with MMR. People with HIV or AIDS should normally receive MMR vaccine. Measles, mumps, and rubella vaccines may be administered as individual shots, if necessary, or as a measles-rubella combination.
    Vaccination, mumps: See Vaccination, MMR. Vaccination, pneumococcal pneumonia: This vaccine, which prevents one of the most common and severe forms of pneumonia, is usually given only once in a lifetime, usually after the age of 55, to someone with ongoing lung problems (such as chronic obstructive pulmonary disease (COPD) or asthma) or other chronic diseases (including those involving the heart and kidneys). This vaccination would rarely be given to children.

    Vaccination, polio: The vaccines available for vaccination against polio are OPV (Oral Polio Vaccine) and IPV (Inactivated Polio Vaccine). OPV is still the preferred vaccine for most children. As its name suggests, it is given by mouth. IPV, or Inactivated Polio Vaccine is given as a shot in the arm or leg. Infants and children should be given four doses of OPV. The doses are given at 2 months, 4 months, 6-18 months and 4-6 years of age. Persons allergic to eggs or the drugs neomycin or streptomycin should receive OPV, not the injectable IPV. Conversely, IPV should be given If the vaccine recipient is on long-term steroid (cortisone) therapy, has cancer, or is on chemotherapy or if a household member has AIDS or there is an unimmunized adult in the house.
    Vaccination, rubella: See Vaccination, MMR.
    Vaccineation, serum hepatitis: See Vaccination, hepatitis B.
    Vaccination, Td: Td is the vaccine given to children over six and adults as boosters for immunity to diphtheria and tetanus.
    Vaccination, varicella zoster: See Vaccineation, chickenpox.
    Vaccination, DPT: DPT immunization protects from diphtheria, pertussis (whooping cough), and tetanus and is given in a series of 5 shots at 2, 4, 6, 18 months of age and 4-6 years of age. Thanks to vaccination programs, these diseases have become less common. However, there are still unvaccinated individuals capable of carrying and passing diphtheria and pertussis to others who are not vaccinated. Tetanus bacteria are prevalent in natural surroundings, such as contaminated soil. See also Vaccination, DTaP.
    Vaccine, flu: The flu (influenza) vaccine is recommended for persons at high risk for serious complications from influenza infection, including everyone 65 or over; people with chronic diseases of the heart, lung or kidneys, diabetes, immunosuppression, or severe forms of anemia; residents of nursing homes and other chronic-care facilities, children and teenagers taking aspirin therapy (and who may therefore be at risk for developing Reye syndrome after an influenza infection), and those in close or frequent contact with anyone at high risk. Persons with an allergy to eggs should not receive influenza vaccine.
    Vaccine, influenza: See Vaccine, flu. Vaccination, DTaP: Like DPT, DTaP protects from diphtheria, pertussis (whooping cough) and tetanus. DTaP is the same as DTP, except that it contains only acellular pertussis vaccine which is thought to cause fewer of the minor reactions associated with immunization and is also probably less likely to cause the more severe reactions occasionally seen following pertussis vaccination. DTaP is currently recommended only for the shots given at 18 months and 4-6 years of age. Vaccination, DT: DT (diphtheria and tetanus) vaccine does not protect from pertussis and is usually reserved for individuals who have had a significant adverse reaction to a DPT shot or who have a personal or family history of a seizure disorder or brain disease.
    Vaccination, hepatitis A: When immediate protection against hepatitis A (infectious hepatitis) is needed, immunoglobulins are used. Protection is effective only if given within 2 weeks of exposure and lasts but 2-4 months. Immunoglobulins can be used to protect household contacts of someone with acute viral hepatitis and travelers to regions with poor sanitation and high hepatitis A rates, when the traveler has to depart sooner than the vaccines can take effect (about 2 weeks). Travelers can receive the immunoglobulin and vaccine simultaneously and be protected immediately and for longer term. When immediate protection is not needed, hepatitis A vaccines are cons idered for individuals in high-risk settings,
    Vaccination, German measles: See Vaccination, MMR.
    Vaccination, Haemophilus influenzae type B: See Vaccination, HIB.

    Vagina: The muscular canal extending from the cervix to the outside of the body. The word "vagina" is a Latin word meaning "a sheath or scabbard", a scabbard into which one might slide and sheath a sword. The "sword" in the case of the anatomic vagina was the penis. Love and war, it would seem, have been connected in the minds of people for millenia.
    Vaginal hysterectomy: Removal of the uterus through a surgical incision, not of the abdomen but, within the vagina. With a vaginal hysterectomy, the scar is not outwardly visible. A vaginal hysterectomy is as opposed to an abdominal hysterectomy.
    Vagina, septate: A vagina that is divided, usually longitudinally, to create a double vagina. This situation can be easily missed by the patient and even by the doctor on exam. If the patient becomes sexually active prior to diagnosis, one of the vaginas stretches and becomes "dominant". The other vagina slips slightly upward and flush and is a little difficult to enter.
    Vaginitis: Inflammation of the vagina. The vagina is the muscular canal extending from the cervix to the outside of the body.
    VAQTA: A vaccine against hepatitis A made of killed hepatitis A virus to stimulate the body’s immune system to produce antibodies against the hepatitis A virus.
    Varicella: A highly infectious viral disease, known familiarly as chickenpox. The "pox" of chickenpox is no major matter unless infected (through scratching) or occur in an immunodeficient person. However, there can be very major complications from chickenpox including pneumonia and encephalitis, particularly in adults but also sometimes in children. Reactivation of the same herpes virus to cause inflammation along a nerve of sensation is reponsible for shingles (zoster). The current aim in the U.S. is to achieve universal (or nearly universal) immunization of children with the chickenpox vaccine.
    Varicella vaccination: See Vaccination, chickenpox.
    Varicocele: Elongation and enlargement of the veins of the pampiniform plexus (the network of veins leaving the testis which join to form the testicular vein). Appears bluish through the scrotum and feels like a bag of worms. Can cause pain or discomfort.
    Varix: An enlarged and convoluted vein, artery or lymphatic vessel.
    Vasa previa: The umbilical cord vessels come before the fetal head during delivery.
    Vascular headache: A group of headaches felt to involve abnormal sensitivity of the blood vessels (arteries) in the brain to various triggers which results in rapid changes in the artery size due to spasm (constriction). Other arteries in the brain and scalp then open (dilate), and throbbing pain is perceived in the head. Migraine headaches are the most common type of vascular headache.
    Vascular endothelial growth factor (VEG-F): A gene that is responsible for the growth of blood vessels.
    Vasoconstriction: Narrowing of the blood vessels resulting from contracting of the muscular wall of the vessels. The opposite of vasodilation.
    Vasodilation: Widening of blood vessels resulting from relaxation of the muscular wall of the vessels. What widens is actually the diameter of the interior (the lumen) of the vessel. The opposite of vasoconstriction.
    Vasodilators: Agents that act as blood vessel dilators (vasodilators) and open vessels by relaxing their muscular walls. For example, nitroglycerin is a vasodilator. So are the ACE (angiotensin converting enzyme) inhibitors.
    Vector: In medicine, a vector is a carrier. The best way to understand a vector is to recall its origin as a word. Vector is the Latin word for a "bearer." It is often an intermediary vehicle. For example, in malaria where the mosquito serves as a vector that carries and transfers the infectious agent (Plasmodium) injecting it with a bite. In molecular biology, a vector may be a virus (or a plasmid); a piece of foreign DNA is inserted in the vector genome to be carried and introduced into a recipient (host) cell. In physics, there are vectors but they go beyond the biomedical realm.
    VEG-F: Vascular endothelial growth factor.
    Vein: A vein is a blood vessel that carries blood low in oxygen content from the body to the lungs and heart. It is part of the circulatory system.
    Velo-cardio-facial (VCF) syndrome: Also known as Shprintzen syndrome, this > is a congenital malformation (birth defect) syndrome with cleft palate, heart defect, abnormal face, and learning problems. The condition is therefore called the velo-cardio-facial (VCF) syndrome. (The velum is the soft palate). Other less frequent features include short stature, small-than-normal head (microcephaly), mental retardation, minor ear anomalies, slender hands and digits, and inguinal hernia. The cause is usually a microdeletion in chromosome band 22q11.2, just as in DiGeorge syndrome. VCF and DiGeorge syndromes are different clinical expressions of essentially the same chromosome defect. of essentially the same chromosome defect.
    Velvet ant stings: Common in most parts of the world including the Southern and Southwestern United States, velvet ants are not true ants but rather parasitic wasps. Their sting—like that of other wasps, fire ants, bees, yellow jackets, and hornets -- can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A’s" of insect allergy are Adrenaline, Avoidance and Allergist.)
    Vena cava: The superior vena cava is the large vein which returns blood to the heart from the head, neck and both upper limbs. The inferior vena cava returns blood to the heart from the lower part of the body.
    Venereal: Having to do with sexual contact. The word venereal comes from Venus, the Roman godess of love. A venereal disease (a morbus venereus) is contracted and transmitted by sexual contact.
    Venereal warts: Warts confined primarily to the moist skin of the genitals due to viruses belonging to the family of human papilloma viruses (HPVs) transmitted through sexual contact. Most infected people have no symptoms but these viruses increase a woman’s risk for cancer of the cervix. The virus can also be transmitted from mother to baby during childbirth. HPV infection is the most common sexually transmitted disease in the United States. It is also the leading cause of abnormal PAP smears and pre-cancerous changes of the cervix in women. There is no cure for genital warts virus infection. Once contracted, the virus can stay with a person for life.
    Ventral: The front or anterior side of a structure.
    Ventricular arrhythmias: Abnormal rapid heart rhythms (arrhythmias) that originate in the lower chambers of the heart (the ventricles). Ventricular arrhythmias include ventricular tachycardia and ventricular fibrillation. Both are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack.
    Ventricular fibrillation: An abnormal irregular heart rhythm whereby there are very rapid uncoordinated fluttering contractions of the lower chambers (ventricles) of the heart. Venticular fibrillation disrupts the synchrony between the heartbeat and the pulse beat. Ventricular fibrillation is most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack. It is life threatening. Ventricular fibrillation is most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack. It is life threatening.
    Ventricular septal defect (VSD): A hole in the interventricular septum, the wall between the ventricles, the lower chambers of the heart. Commonly called a VSD. VSDs constitute a class of heart deformity that is present at birth (congenital cardiac malformation).
    Ventricular septum: The wall separating the lower chambers (the ventricles) of the heart. Also called the interventricular septum.
    Ventricular tachycardia: An abnormal heart rhythm that is rapid, regular and originates from an area of the ventricle, the lower chamber of the heart. Ventricular tachycardias are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack.

    Ventilator: A ventilator is a machine which mechanically assists patients in the exchange of oxygen and carbon dioxide (sometimes referred to as artificial respiration).
    Ventricles: Chambers of an organ. For example, the four connected cavities (hollow spaces) in the central brain or the four chambers of the heart.
    Vertebra: A vertebra is one of 33 bony segments that form the spinal column of humans. There are 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused into one sacrum bone) and 4 coccygeal (fused into one coccyx bone).
    Vertex: The top of the head, in medicine. In Latin, vertex means a whirlpool, whirlwind, top of the mountain, or top of the head, it is thought, because the hairs there often form a whorl. In a vertex delivery, the top of the head comes first.
    Vesical: Refers to the urinary bladder. The word comes from the Latin vesica meaning a bag or bladder.
    Vesicle: A small skin blister, in dermatology. A small pouch, in anatomy. The word vesicle comes from the Latin diminuitive vesiculum meaning a small bag or bladder.
    Vesicular: The adjective for vesicle. A vesicular rash has small blisters on the skin.
    Vesicular rickettsiosis: A mild infectious disease first observed in New York City, caused by Rickettsia akari, transmitted from its mouse host by chigger or adult mite bites. There is fever, a dark spot that becomes a small ulcer at the site of the bite, swollen glands (lymphadenopathy) in that region, and a raised blistery (vesicular) rash. Also known as rickettsialpox.
    Viral hepatitis: Liver inflammation caused by viruses. Specific hepatitis viruses have been labeled A, B, C, D, E, F, and G. While other viruses can also cause hepatitis, their primary target is not the liver.
    Virus: A virus is a microbe which cannot grow or reproduce apart from a living cell. It is smaller in size than a bacterium. Viruses cause most of the common human infections, but are also responsible for causing many rare illnesses. Examples of viral illnesses include the common cold and acquired immunodeficiency disease syndrome (AIDS).
    Virus, human papilloma (HPV): A family of over 60 viruses responsible for causing warts. The majority of the viruses produce warts on the hands, fingers, and even the face. Most of these viruses are innocuous, causing nothing more than cosmetic concerns. Several types of HPV are confined primarily to the moist skin of the genitals, producing genital warts and elevating the risk for cancer of the cervix. These viruses that cause wartlike growths on the genitals and contribute to cancer of the cervix are sexually transmitted. 
     
    Viruses: Small living particles that can infect cells and change how the cells function. Infection with a virus can cause a person to develop symptoms. The disease and symptoms that are caused depend on the type of virus and the type of cells that are infected.
    Vital: Necessary to maintain life. Breathing is a vital function.

    Vitamins: Essential nutrients of food required for normal metabolism in the body. Lack of a vitamin in the diet can lead to a vitamin deficiency disease. Overly high doses of some vitamins can also lead to disease.
    Vitamin A: Retinol. Carotene compounds reponsible for transmitting light sensation in the retina of the eye. Deficiency leads to night blindness. 
    Beta carotene: An antioxidant which protects cells against oxidation damage that can lead to cancer. Beta carotene is converted, as needed, to vitamin A. Food sources of beta carotene include vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables; and fruit such as cantaloupes and apricots. Excessive carotene in the diet can temporarily yellow the skin, a condition called carotenemia, commonly seen in infants fed largely mushed carrots. 
    Vitamin B1: Thiamin, acts as a coenzyme in body metabolism. Deficiency leads to beriberi, a disease of the heart and nervous system. 
    Vitamin B2: Riboflavin, essential for the reactions of coenzymes. Deficiency causes inflammation of the lining of the mouth and skin. 
    Vitamin B3: Niacin, an essential part of coenzymes of body metabolism. Deficiency causes inflammation of the skin, vagina, rectum and mouth, as well as mental slowing. 
    Vitamin B6: Pyridoxine, a cofactor for enzymes. Deficiency leads to inflammation of the skin and mouth, nausea, vomiting, dizziness , weakness and anemia. 
    Folate (folic acid): Folic acid is an important factor in nucleic acid synthesis (the genetic material of all cells). Deficiency leads to megaloblastic anemia. 
    Vitamin B12: An essential factor in nucleic acid synthesis (the genetic material of all cells). Deficiency leads to megaloblastic anemia, as can be seen in pernicious anemia. 
    Vitamin C: Ascorbic acid, important in the synthesis of collagen, the framework protein for tissues of the body. Deficiency leads to scurvy, characterized by fragile capillaries, poor wound healing, and bone deformity in children. 
    Vitamin D: A steroid vitamin which promotes absorption and metabolism of calcium and phosphorus. Under normal conditions of sunlight exposure, no dietary supplementation is necessary because sunlight promotes adequate vitamin D synthesis in the skin. Deficiency can lead to osteomalcia in adults and bone deformity (rickets) in children. 
    Vitamin E: Deficiency can lead to anemia. 
    Vitamin K: An essential factor in the formation of blood clotting factors. Deficiency can lead to abnormal bleeding. 
    Vocal cords: Two small bands of muscle within the larynx. They close to prevent food from getting into the lungs, and they vibrate to produce the voice. 
    Void: To urinate. Just as we can void a check and empty it of value, so can we void our bladder and empty it of urine. According to Merriam Webster’s Collegiate Dictionary, the intransitive form of the verb "void" means "to eliminate solid or liquid waste from the body." We do not agree with this definition. "Void" in this sense is only applied to "liquid waste" (urine), never to "solid waste’ (feces).
    Vomit: Vomit is the ejected matter from the stomach which occurs with symptoms of nausea. When reddish or coffee-ground colored it can represent serious internal bleeding.
    von Recklinghausen’s disease: Hereditary disorder characterized by cafe-au-lait (coffee-with-milk spots on the skin and a tendency to develop nerve tumors) also known as neurofibromatosis.
    VSD: Ventricular septal defect. Please see: Ventricular septal defect.
    Vulva: The external genitalia of the female.

  • Wart: A local growth of the outer layer of skin caused by a virus. Warts that occur on the hands or feet are called common warts. Genital (venereal) warts are located on the genitals and are transmitted by sexual contact.
    Warts, genital: Warts confined primarily to the moist skin of the genitals due to viruses belonging to the family of human papilloma viruses (HPVs) transmitted through sexual contact. Most infected people have no symptoms but these viruses increase a woman’s risk for cancer of the cervix. The virus can also be transmitted from mother to baby during childbirth. HPV infection is the most common sexually transmitted disease in the United States. It is also the leading cause of abnormal PAP smears and pre-cancerous changes of the cervix in women. There is no cure for genital warts virus infection. Once contracted, the virus can stay with a person for life.
    Wart, venereal: The same as a genital wart.
    Wasp stings: Stings from wasps and other large stinging insects such as bees, hornets and yellow jackets can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A’s" of insect allergy are Adrenaline, Avoidance and Allergist.)
    WBC: Commonly used abbreviation for a white blood cell.
    Werner-His disease: Named for the German physician Heinrich Werner (not the Werner of Werner’s syndrome) and the Swiss physician Wilhelm His, Jr. (who described the bundle of His in the heart). See Fever, Wolhynia.
    Western blot: A technique in molecular biology, used to separate and identify particular proteins. Called a Western blot merely because it has some similarity to a Southern blot (which is named after its inventor, the British biologist M.E. Southern).
    White blood cells: White blood cells (WBCs) are cells which circulate in the blood and lymphatic system and harbor in the lymph glands and spleen. They are part of the immune system responsible for both directly (T cells and macrophages) and indirectly (B cells producing antibodies) attacking foreign invaders of the body.
    White matter: The part of the brain that contains myelinated nerve fibers. The white matter is white because it is the color of myelin, the insulation covering the nerve fibers. The white matter is as opposed to the gray matter (the cortex of the brain which contains nerve cell bodies).
    Whooping cough: Also known as pertussis, this is a feared infectious disease that can strike the respiratory system and affect other organs of the body. It has three stages—an initial stage with watery runny nose and eyes, a progressive cough stage with characteristic (sometimes severe) coughing spells, and (if the dhild survives) a recovery stage. The disease may last for 2-6 weeks. Therapy is supportive and many young infants need hospitalization if the coughing becomes severe. Immunization with DPT (diphtheria-pertussis-tetanus) vaccine provides protection. With pertussis, an ounce of prevention is worth a pound of cure (or, if you are metrically inclined, a gram of prevention is worth a kilo of cure). Have your child immunized!
    Will, living: A living will is one form of advance medical directive. Advance medical directives preserve the person’s right to accept or reject a course of medical treatment even after that person becomes mentally or physically incapacitated to the point of being unable to communicate those wishes. There are two basic forms of advance directives: (1) a living will, in which the person outlines specific treatment guidelines that are to be followed by health care providers; (2) a health care proxy (also called a power of attorney for health-care decision-making) in which the person designates a trusted individual to make medical decisions in the event that he or she becomes too incapacitated to make such decisions. Advance directive requirements vary greatly from one jurisdiction to another and should therefore be drawn up in consultation with an attorney who is familiar with the laws of the particular jurisdiction. (This entry is based upon material from the National MS Society).
    WNL: Within normal limits. A laboratory test result may for instance be WNL.
    Wolhynia fever: Trench fever, a louse-borne disease first recognized in the trenches of World War I, again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E. Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or outer layer of the whites of the eyes (conjunctiva). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Also called shin bone fever, quintan fever, five-day fever, Meuse fever, His’ disease, His-Werner disease, Werner-His disease.
    Wordprocessor’s cramp: A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs during typing or wordprocessing. Similar focal dystonias have also been called writer’s cramp, pianist’s cramp, musician’s cramp, and golfer’s cramp.
    Writer’s cramp: A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs during handwriting. Similar focal dystonias have also been called typist’s cramp, pianist’s cramp, musician’s cramp, and golfer’s cramp.
    Wry neck: Medically called spasmodic torticollis, or torticollis. The most common of the focal dystonias. In torticollis, the muscles in the neck that control the position of the head are affected, causing the head to twist and turn to one side. In addition, the head may be pulled forward or backward.

    Wt: Weight. Wt 80 lbs = weight 80 pounds.
  • X: Although the letter X is used as a symbol in various ways (such as X-rays, the X-axis of a graph, etc.), today "the X " usually refers to the X chromosome. 
    X chromosome: The sex chromosome found twice in normal females and singly, along with a Y chromosome, in normal males.
    X-linked: On the X chromosome. "Linked" in genetics does not mean merely associated. An X-linked gene travels with the X chromosome and therefore is part of the X chromosome.
    X-ray: High-energy radiation. It is used in low doses to diagnose diseases and in high doses to treat cancer.
    X-ray, AP: An X-ray picture in which the beams pass from front-to-back (anteroposterior). An AP film is as opposed to a PA (posteroanterior) film in which the rays pass through the body from back-to-front.
    X-ray, lateral: An X-ray picture taken from the side.
    X-ray, PA: An X-ray picture in which the beams pass from back-to-front (posteroanterior). By contrast an AP (anteroposterior) film is one in which the rays pass through the body from front-to-back.
    Xanthelasma: Tiny 1-2 mm yellowish plaques that are slightly raised on the skin surface of the upper or lower eyelids. Xanthelasma is caused by tiny deposits of fat in the skin and is often associated with abnormal blood fat levels (hyperlipidemia).
    Xanthoma: Yellowish firm nodules in the skin frequently indicating underlying disease, such as diabetes, disorder of fats (lipid disorder or hyperlipidemia), or other conditions.
    Xeroderma: Abnormally dry skin.
    Xerophagia: Eating a dry diet.
    Xeropthalmia: Dry eyes. Also, called conjunctivitis arida. Xeropthalmia can be associated with systemic diseases (such as Sjogren’s syndrome, systemic lupus erythematosus, rheumatoid arthritis, scleroderma, sarcoidosis, amyloidosis, hypothyroidism, and others) or deficiency of vitamin A. Xeropthalmia results from inadequate function of the lacrimal glands which supply water to produce tears.

    Xerostomia: Dry mouth. Xerostomia can be associated with systemic diseases (such as Sjogren’s syndrome, systemic lupus erythematosus, rheumatoid arthritis, scleroderma, sarcoidosis, amyloidosis, hypothyroidism, and others). Xerostomia results from inadequate function of the salivary glands, such as the parotid glands.
  • Y (in chemistry): The symbol for the element yttrium, an ultrarare metal named after Ytterby in southern Sweden. Yttrium has been used in certain nuclear medicine scans.
    Y (in genetics): The Y chromosome, the sex chromosome found in normal males, together with an X chromosome.
    Y chromatin: Brilliantly fluorescent body seen in cells stained with the dye quinacrine which lights up the Y chromosomes most brightly.
    YAC: Yeast artificial chromosome.
    Yard: In length, 3 feet or 36 inches or, metrically, 86.44 centimeters. The yard, along with the foot and inch, are English creations to which the USA has stubbornly clung. The yard was originally a unit of measurement of land and was about 5 meters (now termed a rod). In the 14th century, the yard emerged as 3 feet, about the length of a riding stick or sword. <