Collagenous colitis in an adult patient with chronic diarrhoea: case report

Collagenous colitis is an established cause of chronic watery diarrhoea of unknown aetiopathogenesis, characterised by normal colonic endoscopic findings, and a prominent collagen band in the sub-epithelial layer on colonic mucosal histology. We report a case of a 65-year old male who presented with recurrent episodes of watery diarrhoea of 38 years duration. There was a positive family history of similar diarrhoea in the mother and two siblings. Colonoscopy done was macroscopically unremarkable except for a redundant sigmoid colon. Mucosal biopsy of the rectum and colon showed at histology atrophy of the mucosal lining, infiltration of the lamina propria by plasma cells and lymphocytes, and a thick band of collagenous tissue in the sub-epithelial zone of the lining mucosa. A high index of suspicion is necessary to make the diagnosis in patients with chronic diarrhoea, especially when common causes of chronic diarrhoea like intestinal parasitoses, HIV/AIDS, diabetic autonomic neuropathy, thyrotoxicosis have been excluded. It is suggested that colonoscopic examination with adequate biopsy should be performed in patients with chronic diarrhoea with no aetiologic agent identified.