Primary eosinophilic colitis as an unusual cause of chronic diarrhea.

1-year history of watery diarrhea and gradual weight loss. One week before admission, the frequency of watery diarrhea increased up to six times per day, accompanied by hematochezia and lower abdominal pain. The patient denied any prior history of systemic disease or medications. Laboratory evaluation revealed normal leukocyte count (8.7 × 109/L [normal 4.0–10.8 × 109/L]) with marked peripheral blood eosinophilia (15%). Multiple stool tests were negative for bacterial or parasitic infections, and no evidence of malignancy or other systemic disease was noted during the comprehensive workup. Colonoscopy revealed patchy subepithelial hemorrhages, friability, submucosal edema, and loss of vascularity in the transverse colon and left colon (●" Fig. 1). Multiple biopsies were obtained throughout the involved colonic segments and normal-appearing colonic segments. They showed heavy infiltration of tissue eosinophils with more than 30 per high-power field in the lamina propria, highly suggestive of eosinophilic colitis (●" Fig. 2). The patient was diagnosed with primary eosinophilic colitis and was treated with oral prednisolone (1mg/kg per day). Her symptoms resolved greatly within 5 days and the blood eosinophil count normalizedwithin 2weeks.With improvement of symptoms, prednisolone treatment was tapered slowly over the next 3 months. Follow-up endoscopy 2months later showedmarked improvement of the colonic inflammation (●" Fig. 3). The patient has remained well without recurrence of symptoms during the 12months of follow-up. Eosinophilic colitis is an extremely rare form of primary eosinophilic gastrointestinal disorders in adults; not enough epidemiological data exist to establish its true frequency [1]. Diagnosis in older individuals is therefore very difficult unless clinical suspicion is high [2]. The present case suggests that early colonoscopy and multiple endoscopic biopsies can give the definitive clue to diagnosing and treating eosinophilic colitis in adult patients with chronic diarrhea. Primary eosinophilic colitis as an unusual cause of chronic diarrhea