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Anorexia Nervosa

A disorder characterized by a disturbed sense of body image, a morbid fear of obesity, a refusal to maintain a minimally normal body weight, and, in women, amenorrhea.

The etiology is unknown, but social factors appear to be important. Emphasis on the desirability of being thin pervades Western society, and obesity is considered unattractive, unhealthy, and undesirable. About 80 to 90% of prepubertal children are aware of these attitudes, and > 50% of prepubertal girls diet or take other measures to control their weight. However, since only a small percentage develop anorexia nervosa, other factors must be important. Some persons are probably predisposed because of undefined psychologic, genetic, or metabolic vulnerability. Anorexia nervosa is rare in areas with a genuine food shortage.

About 95% of persons with this disorder are female. Onset usually occurs during adolescence, occasionally earlier, and less commonly in adulthood. Many patients belong to middle or upper socioeconomic classes. Mortality rates of 10 to 20% have been reported. However, because most mild cases are probably undiagnosed, true prevalence and mortality rates are unknown.

Symptoms and Signs

Anorexia nervosa may be mild and transient or severe and long-standing. Many persons who develop the disorder are meticulous, compulsive, and intelligent, with very high standards for achievement and success. The first indications of the impending disorder are concern about body weight (even among patients who are lean, which most are) and restriction of food intake. Preoccupation and anxiety about weight increase, even as emaciation develops. Denial of the disorder is a prominent feature. Patients do not complain about anorexia or weight loss, usually resist treatment, and are brought to the physician's attention by their families, by intercurrent illness, or by complaints about other symptoms (eg, bloating, abdominal distress, constipation).

Anorexia is a misnomer, because appetite remains unless the patient becomes cachectic. Patients are preoccupied with food: They study diets and calories; hoard, conceal, and waste food; collect recipes; and prepare elaborate meals for others. Patients are often manipulative, lying about food intake and concealing behavior, such as induced vomiting. Binge eating followed by induced vomiting and the use of laxatives and diuretics (binge-purge behavior--see Bulimia Nervosa, below) occurs in 50% of anorectics. The other 50% simply restrict the amount of food they eat. Most also exercise excessively to control weight.

Patients usually lose interest in sex. Other common findings include bradycardia, low BP, hypothermia, lanugo hair or slight hirsutism, and edema. Even patients who appear cachectic tend to remain very active (including pursuing vigorous exercise programs), are free of symptoms of nutritional deficiencies, and have no unusual susceptibility to infections. Depression is common.

Endocrine changes include prepubertal or early pubertal patterns of luteinizing hormone secretion, low levels of thyroxine and triiodothyronine, and increased cortisol secretion. In a severely malnourished patient, virtually every major organ system may malfunction, but cardiac and fluid and electrolyte disorders are the most dangerous. Cardiac muscle mass, chamber size, and output decrease. Dehydration and metabolic alkalosis may occur, and serum potassium may be low; all are aggravated by induced vomiting and use of laxatives or diuretics. Sudden death, most likely due to ventricular tachyarrhythmias, may occur. Some patients have prolonged QT intervals (even when corrected for heart rate), which, with the risks imposed by electrolyte disturbances, may predispose to tachyarrhythmias.

Diagnosis

Anorexia nervosa is usually apparent from the constellation of symptoms and signs described above, particularly the loss of >= 15% of body weight in a young person who fears obesity, becomes amenorrheic, denies illness, and otherwise appears well. The key to diagnosis is eliciting the central fear of obesity, which is not diminished by weight loss. In females, amenorrhea is required for the diagnosis. In severe cases, marked depression or symptoms suggesting another disorder, such as schizophrenia, may require differentiation. Rarely, a severe physical disorder, such as regional enteritis or a CNS tumor, is misdiagnosed as anorexia nervosa.

Treatment

Treatment has two phases: short-term intervention to restore body weight and save life and long-term therapy to improve psychologic functioning and prevent relapse.

When weight loss has been severe or rapid or when weight has fallen below an arbitrary level (eg, 75% of ideal), prompt restoration of weight becomes crucial, and hospitalization is imperative. If any doubt exists, the patient should be hospitalized. Removing the patient from her home sometimes reverses a downhill course, although more active psychiatric treatment is often required. Tube or parenteral nutrition is rarely necessary.

Once the patient's nutritional, fluid, and electrolyte status has been stabilized, long-term treatment begins. It is complicated by the patient's abhorrence of weight gain, denial of illness, and manipulative behavior. The physician should attempt to provide a calm, concerned, stable relationship while encouraging a reasonable caloric intake. Combined management by the family physician and a psychiatrist often helps, and consultation with or referral to a specialist in eating disorders is wise. Individual psychotherapy--behavioral, cognitive, or psychodynamic--is helpful, as is family therapy for younger patients. Fluoxetine is useful for preventing relapse after weight has been restored.


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