Diagnosis of Food Protein-Induced Enteropathy Based on Gastrointestinal Mucosal Pathology before and after Elimination Diet Therapy: A Case Report.

We describe the case of a 1-year-old girl with food protein-induced enteropathy (FPE) that was difficult to diagnose. She was referred to our hospital with a 3-month history of diarrhea, vomiting, and weight loss. Although her diarrhea improved after a few days of fasting, oral intake of elemental diets, formula milk, or rice porridge resulted in repeated relapses. The serum IgE level was 1028 IU/mL, and radioallergosorbent tests were positive for milk, casein, alpha-lactalbumin, and other allergens. A histopathology of the duodenal mucosa revealed loss of mucosal villous structure, crypt hyperplasia, crypt apoptosis, and lymphocyte and eosinophil infiltration (<20 eos/hpf) into the lamina propria. After prednisolone (PSL) therapy and the complete removal of cows' milk and chicken eggs from her diet, the patient's diarrhea disappeared. Five months after discontinuing oral PSL and complete removal of cows' milk and chicken eggs, the duodenum exhibited normal mucosal villous structure and well-differentiated ducts. No abnormalities were observed in the egg rechallenge; however, diarrhea recurred after the cows' milk rechallenge. Thus, histopathologic examination of the gastrointestinal mucosa is useful for diagnosing FPE similar to oral food challenges, and re-evaluation after elimination diet therapy may be beneficial to rule out other diseases.