An adolescent with chronic giardiasis mimicking anorexia nervosa.

A 13-year-old Hispanic female presented with symptoms of abdominal pain, amenorrhea, and unintentional weight loss of 11 kg. Preliminary investigation yielded no immediate causes, and an initial differential included inflammatory bowel disease (IBD), celiac disease, as well as viral, bacterial, or parasitic gastrointestinal infection. Evaluation of these potential diagnoses yielded negative results; thus, the team thought that the patient may be suffering from anorexia nervosa. The patient was discharged to outpatient care, and was treated in our adolescent health clinic, where repeat laboratory testing yielded a positive Giardia-antigen test. The patient was placed on metronidazole, rapidly gained weight, and resumed menstruation soon after. The final diagnosis was chronic giardiasis. Chronic giardiasis is a rare and enigmatic disease that presents with many symptoms similar to chronic gastrointestinal disorders (e.g. IBD and celiac disease) and anorexia nervosa. Practitioners involved in the diagnosis and treatment of anorexia nervosa should be aware of this disorder and include it in differential diagnoses of patients presenting with anorexia nervosa symptoms.