Collagenous colitis.

A clinical and morphological description of "collagenous colitis" with reference to own cases is given. The disease presents with watery diarrhoea and abdominal pain in middle aged subjects, mostly women. Clinical and laboratory findings are normal. In colo-rectal biopsies there is a severe thickening of the so called "collagen table" in the superficial inter-cryptal lamina propria. Ultrastructural examination shows bandlike subepithelial collagenous fibrils of types I and III. The etiology of this lesion in the large bowel is hitherto unknown. The clinical course seems to be rather benign, requiring only symptomatic treatment.