Mistaken diagnosis of eosinophilic colitis.

A 69-year-old male chronic alcohol abuser suffering from diarrhoea and with a number of discrete pruriginous and erythematous lesions of the trunk was referred to our Unit with a diagnosis of idiopathic eosinophilic colitis in order that we might determine corticosteroid treatment. Diagnosis was based on the presence of marked peripheral eosinophilia and massive eosinophilic infiltration at colonic biopsy, and the exclusion of parasitic infection by means of two different microscopic stool examinations of five samples. However, repeated stool examinations of ten samples collected on separate days and evidence of impaired cell-mediated immunity allowed a definite diagnosis of Strongyloides stercoralis autoinfection or hyperinfection. Due to the poor sensitivity of stool examination in the diagnosis of Strongyloides stercoralis infection, a careful search for this parasite should be made in all patients with comparable clinical findings before formulating a diagnosis of idiopathic eosinophilic colitis, because consequent steroid treatment may have a fatal outcome by inducing widespread dissemination of the parasite.