Cause:Strong genetic component with 50% concordance in monozygotic twins, contribution of perfectionistic personality and anxiety disorders. Dieting behavior a common entry point.
Pathophys:Amenorrhea develops early when <90% ideal body wgt (IBW = 100 lb at 60 inches tall, + 5 lb for each inch over that). Adolescent females show structural brain changes and cognitive impairment long after diagnosis (Peds 2008;122:e426)
Female/male: 20:1; associated with bulimia and depression; prevalence of bulimia/anorexia = 1/5, 0.3-0.5% of young women; prevalence incr w family h/o addictive disorders
Sx:Over 15% weight loss; onset before age 17 yr; calorie restriction, laxative use; diuretic use; excessive exercising; amenorrhea; persistent conviction that too fat no matter how thin; secretive eating
Si:Lanugo hair; thin to cachectic, bradycardia, hypothermia, hypotension, edema, hair loss
Suicide (2-5%); depression; osteoporosis/bone loss (Ann IM 2000;133:790); CHF (starvation—Nejm 1985;313:1457); refeeding syndrome with calorie repletion in up to 6% hosp patients; with CHF and cardiomyopathy (Nejm 1985;313:1457)
r/o Addison’s disease (Nejm 1996;334:46)
Lab:
Chem: Hypokalemia; amylase elevated, sometimes due to pancreatitis, but many times due to salivary origin (lipase and pancreatic fraction normal—Ann IM 1987;106:50); hypophosphatemia; TSH/T4
Hem:CBC for pancytopenia
Noninv:EKG at regular intervals (Peds 2000;105:1100) to detect myocardiopathy; long QT