Differential Diagnosis
Anorexia Nervosa must be distinguished from weight loss caused by medical illnesses such as ne-oplasms, tuberculosis, hypothalamic disease, and primary endocrinopathies (anterior pituitary insufficiency, Addison’s disease, hyperthyroidism, and diabetes mellitus). These can generally be diagnosed on the basis of thorough histories, physical examinations, and laboratory studies. Patients with these medical illnesses do not present with the dread of fatness, unrelenting pursuit of thinness, and hyperactivity that characterize anorexia nervosa.

Weight loss frequently occurs in patients with depressive disorders or certain schizophrenic disorders characterized by peculiar eating habits prompted by delusions about food. Patients with other disorders also lack preoccupations with caloric intake, obsessions with body shape and size, and hyperactivity. Patients with somatization disorder may manifest weight fluctuations, vomiting, and peculiar food habits, but weight loss is usually not severe, and amenorrhea for longer than 3 months is unusual.

To establish the diagnosis of anorexia nervosa, patients should satisfy the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) diagnostic criteria listed in

Table 26-1. Subtyping takes into account the findings that patients with a mixture of anorexia nervosa and bulimia nervosa have a higher association of both Axis I and Axis II comorbidity, present greater medical risks as a result of fluid and electrolyte imbalance, and may have a worse prognosis than patients with anorexia nervosa alone.