RECTAL MUCOSAL MAJOR BASIC-PROTEIN IN INFANTS WITH DIETARY PROTEIN-INDUCED COLITIS

Dietary protein-induced colitis is a frequent cause of rectal bleeding in infants. The exact pathogenic mechanism is unknown but the disorde r has been thought to be due to an allergic response. Rectal mucosal e dema and eosinophilia are typically found but there are no specific ma rkers currently available. Because eosinophil degranulation, as eviden ced by the release of major basic protein, has been implicated in hype rsensitivity disorders, we aimed to assess major basic protein deposit ion as a marker of dietary protein-induced colitis occurring in young infants. Suction rectal biopsies from five infants aged 1 to 7 months with findings consistent with dietary protein-induced colitis were com pared histologically with five age matched controls who underwent rect al biopsies to rule out Hirschsprung's disease. An established indirec t immunofluorescent staining method was used to identify tissue major basic protein. Comparable rectal deposition of major basic protein was found for the controls and colitic patients. Mucosal eosinophilia but not mast cell content was more prominent in the colitic patients (P < .05) than in the controls. Some of the colitic infants had elevated s erum IgE levels (1 of 5), positive RAST for milk (2 of 5), and periphe ral blood eosinophilia (1 of 5). Our findings do not support the conce pt that dietary protein-induced colitis of infancy is due solely to an immediate hypersensitivity response. The results also indicate that m ajor basic protein is probably not a marker or likely primary mediator this disorder.