Accumulation of mast cells in the interstitium of eosinophilic colitis.

INTRODUCTION The mechanism of eosinophilic colitis remains unclear, and no case has been reported in which the number of mast cells was examined. CASE REPORT A 35-year-old man presented to our hospital with chief complaints of chills and consistent watery diarrhea after eating raw fresh-water fish. In blood examination, peripheral blood eosinophilia was found. Histological examination from biopsy specimens of both the ascending colon and rectum showed a prominent eosinophilic infiltration in the intestinal mucosa. Although a provocation test could not be performed due to lack of informed consent, a diagnosis of eosinophilic colitis was made on the basis of other findings. Immunohistochemical staining for human mast cell tryptase using monoclonal antibody against human mast cell tryptase showed an accumulation of mast cells in the colonic interstitium. CONCLUSIONS We report a case of eosinophilic colitis in which an accumulation of mast cells in the colonic interstitium was demonstrated.