Macrophage-associated chronic diarrhea of unknown origin. Preliminary observations.

The distribution of macrophages in the colonic mucosa was investigated in 13 patients with chronic diarrhea. Group I consisted of 5 patients; both colonoscopy and colonic biopsies were reported as normal. Group II included 5 patients with normal colonoscopy, but with collagenous colitis or lymphocytic colitis at histology. Group III consisted of 3 patients with mucosal inflammation at both colonoscopy and histology. Immunostain with CD68 (a macrophage marker) revealed, in all patients from Group I, a linear accumulation of CD68+ macrophages at the top of the lamina propria. In contrast, sections from patients in Groups II and III showed a random distribution of CD68+ macrophages. Since all three groups of patients here investigated had chronic diarrhea, it goes without saying that the linear recruitment of macrophages in Group I may not be the direct cause of chronic diarrhea, as no similar linear recruitment of macrophages was demonstrated in patients with collagenous colitis or with chronic inflammation. Although the cause(s) of chronic diarrhea in patients of Group I remain to be elucidated, it would appear that the recruitment of macrophages along the superficial aspect of the lamina propria mucosa (lpm) is a characteristic cellular response in patients with this subtype of chronic diarrhea.