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Background
Anorexia nervosa is a psychiatric disorder characterized by the refusal to maintain a minimally normal weight, often with severe physiologic consequences. Patients have a profoundly disturbed body image as well as an intense fear of weight gain despite being severely underweight.

Diagnostic criteria for anorexia nervosa in the Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) include the following:

A refusal to maintain body weight at or above a minimally normal weight for age and height (usually less than 85% of ideal body weight)
Intense fear of gaining weight or becoming fat
Disturbance in the way one’s body weight or shape is experienced, with denial of current low body weight
Amenorrhea in postmenarcheal females of at least 3 menstrual cycles
The disorder may be further divided into 2 subtypes: (1) restricting, in which severe limitation of food intake is the primary means to weight loss, and (2) binge-eating/purging type, in which there are periods of food intake that are compensated by self-induced vomiting, laxative or diuretic abuse, or excessive exercise.

Other physiologic causes of malnutrition, weight loss, and amenorrhea must be ruled out to make the diagnosis.

Patients with anorexia nervosa often display other personality characteristics such as a desire for perfection, academic success, lack of age-appropriate sexual activity, and a denial of hunger in the face of starvation. Psychiatric characteristics include excessive dependency needs, developmental immaturity, social isolation, obsessive-compulsive behavior, and constriction of affect. Many patients also have comorbid mood disorders, with depression and dysthymic disorder being most prevalent.

Pathophysiology
Anorexia nervosa is the result of a complex interplay between biological, psychological, and social factors, which tend to affect women more than men, and adolescents more than older women. Some evidence suggests a higher rate of the disorder in monozygotic twins than in dizygotic twins, which may indicate a biologic predisposition.

Psychologically, prepubescent patients who subsequently develop anorexia nervosa have a high incidence of premorbid anxiety disorders. The onset of the disorder during puberty has led to the theory that, by exerting control over food intake and body weight, adolescents are attempting to compensate for a lack of autonomy and selfhood.

The patient’s altered body image results in a perception of fatness despite being normal or underweight. Attempts to correct this flaw through food restriction or purging lead to progressive starvation. Modern preoccupation with slenderness and beauty in the Western world may contribute to the mindset of slenderness as a valued quality in adolescents; however, this link has not been proven.

Malnutrition subsequent to self-starvation leads to protein deficiency and disruption of multiple organ systems. In addition to hypoglycemia and vitamin deficiencies, starvation results in release of endogenous opioids, hypercortisolemia, and thyroid function suppression. Neuroendocrine disturbances result in delayed puberty, amenorrhea, anovulation, low estrogen states, increased growth hormone, decreased antidiuretic hormone, hypercarotenemia, and hypothermia. Decreased gonadotropin levels and hypogonadism may occur among males who are affected.

Cardiovascular effects include mitral valve prolapse, supraventricular and ventricular dysrhythmias, long QT syndrome, bradycardia, orthostatic hypotension, and shock due to congestive heart failure.

Renal disturbances include decreased glomerular filtration rate (GFR), elevated BUN, edema, acidosis with dehydration, hypokalemia, hypochloremic alkalosis with vomiting, and hyperaldosteronism.

Gastrointestinal findings include constipation, delayed gastric emptying, and gastric dilation and rupture. Patients who induce vomiting develop dental enamel erosion, palatal trauma, enlarged parotids, esophagitis, Mallory-Weiss lesions, and elevated transaminases.

Frequency
United States
The lifetime prevalence of anorexia nervosa in the United States is estimated at 0.3-1%; however, some studies have shown rates as high as 4% among women. The rates among men are estimated at 0.1%. As many as 5% of young women exhibit symptoms of anorexia but do not meet full diagnostic criteria.

International
Anorexia nervosa is found in all developed countries and in all socioeconomic classes at similar rates (0.3-1% in women, 0.1% in men).

Mortality/Morbidity
Anorexia nervosa has one of the highest mortality rates of all psychiatric disorders, with rates reported from 5-18%. Patients with restricting subtype tend to have more resistance to recovery.

Approximately 50% of patients will recover with treatment and maintain a normal weight but often not without relapses and multiple treatment modalities. Mortality is often due to suicide and less frequently to complications of starvation.

Race
Anorexia nervosa is significantly more frequent in white populations than in people of other races, but it has been reported among all races.

A link between socioeconomic class and prevalence of eating disorders has not been demonstrated in the literature.

Sex
Female-to-male ratio is 10-20:1 in developed countries.

In some professions, the frequency is much higher among men (wrestling, running, modeling) than the general male population.

Age
Anorexia nervosa is primarily a phenomenon of puberty and early adulthood. Eighty-five percent of patients have onset of the disorder between the ages of 13 and 18 years.

Anorexia nervosa has been observed in both the very young and very old. Patients who are older at the time of onset of the disorder have a worse prognosis.

Clinical
History
Patients may present to the ED with extreme weight loss, food refusal, dehydration, weakness, or shock. Many present at the urging of family members or friends and are in deep denial of their malnutrition and illness.

Patients should be questioned about their current weight, highest weight, lowest weight, exercise habits, and menstrual cycles. Further questioning should inquire with regard to eating habits, presence or absence of self-induced vomiting/binge eating, etc.
Major depression and dysthymic disorder have been reported in up to 50% of patients with anorexia nervosa. Patients should be asked about early morning awakening, tearfulness, and thoughts of suicide or a plan.
Review of systems is often positive for constipation, early satiety, hypothermia, nausea, hair loss, and fatigue.
Physical
Patients may present anywhere along the spectrum of weight loss. They may attempt to hide their weight loss by wearing bulky clothing or many layers.

Physical examination may reveal hypothermia, peripheral edema, thinning hair, and obvious emaciation.
Behaviorally, a patient may demonstrate a flat affect and display psychomotor retardation, especially in the later stages of the disease.
Vital sign abnormalities may include hypothermia, bradycardia, and hypotension.
Cardiac examination may reveal the mid-systolic click of mitral valve prolapse.
Patients with purging behavior may have parotid gland hypertrophy, dental enamel erosion and, in extreme cases, seizures from electrolyte disturbances.
Dermatologic examination reveals dry skin, lanugo (a fine, downy covering of hair on the extremities), and poor skin turgor.
Causes
Anorexia nervosa is a complex combination of biological, psychological, and social factors, which have devastating physical and mental consequences.

Some evidence suggests that biologic risk factors include a first-degree relative with an eating disorder and higher rates of the disorder in monozygotic than dizygotic twins.
A psychological profile often demonstrates premorbid anxiety disorders as well as more severe affective disorders such as major depression and dysthymic disorder. Patients may also have symptoms of obsessive-compulsive disorder, with rigid and ritualistic eating behaviors