Abnormalities in the apparently normal bowel mucosa in Crohn's disease.

The uninvolved intestinal mucosa away from the affected areas in Crohn's disease has always been considered to be macroscopically and microscopically normal. Rectal biopsy specimens from 13 patients who had had Crohn's, disease elsewhere in the bowel, but never in the rectum, showed significant increases in the plasma-cell density in the lamina propria, in the volume of the lamina propria, and in the glucosamine-synthetase activity of the specimens, compared with a control series of patients with the irritable-colon syndrome. It is suggested that the colonic mucosa is always abnormal in Crohn's disease even if macroscopical and histological examination shows an apparently normal mucosa.