Definition An emotional disorder characterized by severe and potentially life-threatening weight loss through self-induced reduction in total food intake. More than 90% of reported cases occur in women in industrialized countries where thin bodies are considered attractive, though anorexia now occurs in a growing number of men. Although seldom appearing prior to puberty, associated mental [...]
Definition Angioedema is a well-circumscribed, nonpitting swelling of the subcutaneous tissues of the skin and mucosa, which is typically nonpruritic. Sites of involvement include eyelids, lips, tongue, larynx, palms, soles, genitalia, and gastrointestinal tract. The condition results from the activity of inflammatory mediators that cause dilation and enhanced permeability of venules and capillaries. Sources of [...]
Definition Angina pectoris, or angina, is chest pain caused by underlying coronary heart disease resulting in myocardial ischemia. Different types include the following. Stable angina (“classic”) occurs with exercise, emotional stress, or extreme temperatures. It seldom is associated with permanent damage to the heart muscle. Unstable angina occurs even at rest. Patients may present with [...]
Definition Anemia is characterized by a reduction in either the hematocrit (red blood cell [RBC] volume <42% in men and <36% in women) or the concentration of hemoglobin (<14 g/dL in men and <12 g/dL in women). The prevalence of anemia is highest among menstruating women (5.8%), infants (5.7%), and the elderly (12%). Anemias can [...]
Definition Anaphylaxis, meaning “without protection,” is a systemic, potentially life-threatening hypersensitivity reaction. It occurs abruptly and variably, as a result of an IgE-mediated release of histamine and other mediators from mast cells and basophils in previously sensitized individuals. The severe allergic response is a medical emergency and is estimated to be responsible for more than [...]
Definition Amyloidosis describes a heterogeneous group of diseases, all characterized by the extracellular deposition of fibrillar, proteinaceous material in organs and tissues, either locally or systemically. The following four major classes of systemic amyloidosis are differentiated by the nature of the precursor plasma proteins that form the fibril deposits: Immunoglobulin light chain or “primary” amyloidosis [...]
Definition Amenorrhea is the absence of menses. Primary amenorrhea is defined as the failure of menses to begin once a woman reaches 16 years of age, whether or not other pubertal changes such as breast development/pubic or axillary hair are present. Secondary amenorrhea is the absence of menses for the length of time equal to [...]
Definition Alzheimer’s disease (AD) is the most common cause of dementia in the elderly, affecting at least three to four million people in the United States. AD is defined as memory loss with at least one other area of cognitive impairment (e.g., language, attention, orientation, self-monitoring, judgment, motor skill, inability to perform daily activities). Memory [...]
Definition Alopecia is the absence or thinning of hair in an area of the body where hair formerly grew. It may be caused by physical damage to the hair itself or to the hair follicles, but is most often the result of changes in the natural hair growth cycle. The average scalp has about 100,000 [...]
Definition Allergic rhinitis (hay fever) is a reaction to airborne allergens. It affects between 1:6 and 1:10 Americans and is an IgE-mediated disorder of the immune system; 70% of cases occur before age 30. Symptoms resemble those of viral rhinitis but persist and show seasonal variation. This most common form of allergy involves the entire [...]
