Dictionary

ad- Prefix indicating toward or in the direction of. For example, adduction is the movement of a limb toward the midline of the body, and adrenal literally means “toward the kidney.”

acyclovir A potent antiviral drug or medication (brand name: Zovirax) that works against several human herpes viruses, Epstein-Barr virus, herpes zoster, varicella (chickenpox), cytomegalovirus, and other viruses. It is part of the AIDS drug AZT. See also AZT.

acute-phase protein A protein whose plasma concentrations increase during certain inflammatory disorders. Perhaps the best-known acute-phase protein is C-reactive protein (CRP).

acute thrombocytopenic purpura Sudden onset of low blood platelet levels, with bleeding into the skin and elsewhere. Abbreviated ATP. ATP can have many causes; for example, it can be a potentially serious complication during the acute phase of measles infection.

acute respiratory distress syndrome Respiratory failure of sudden onset due to fluid in the lungs (pulmonary edema), following an abrupt increase in the permeability of the normal barrier between the capillaries in the lungs and the air sacs. The muscles used in breathing are forced to work harder, causing labored and inefficient breathing. An abnormally…

acute otitis media Painful inflammation of the middle ear, typically with fluid in the middle ear, behind a bulging eardrum or a perforated eardrum, often with drainage of pus. The customary treatment is antibiotics for 7 to 10 days. After antibiotic treatment, some children are left with fluid in the middle ear, which can cause…

acute nonlymphocytic leukemia See leukemia, acute myeloid.

acute myocardial infarction A heart attack that occurs when the heart muscle is suddenly deprived of circulating blood. Abbreviated AMI. See also heart attack.

acute myelogenous leukemia See leukemia, acute myeloid.

acute mountain sickness The physical effect of being in a high-altitude environment. Abbreviated AMS, it is common at altitudes above 2,440 meters (approximately 8,000 feet). Three-fourths of people have mild symptoms of AMS at altitudes over 3,048 meters (approximately 10,000 feet). Occurrence depends on the altitude, rate of ascent, and individual susceptibility. Symptoms begin 12…

acute membranous gingivitis A progressive and painful infection of the mouth and throat due to the spread of infection from the gums. Symptoms include ulceration, swelling, and sloughing off of dead tissue from the mouth and throat. Certain germs (including fusiform bacteria and spirochetes) have been thought to be involved, but the actual cause is…

acute leukemia Cancer of the blood cells that characteristically comes on suddenly and, if not treated, progresses quickly. In acute leukemia, the leukemic cells are not able to mature properly.