With an incidence of 5.2 per 100,000, collagenous colitis has a female preponderance and peaks at the age of 50–70 years and female to male ratio of 9:1. It is associated with HLA B8/HLA DR3 and shows increased expression of HLA1. The underlying pathogenesis is decreased levels of interstitial collagenase which leads to reduced matrix degradation which in turn results in accumulation of matrix proteins and this causes defective sodium and chloride absorption. Diagnosis is based upon microscopic analyses of colonic biopsies. The characteristic histopathological finding is the collage band thickening that mainly occurs in the caecum and transverse colon in over 80% cases and in the rectum is lesser than 30%. Blood and urine cultures are usually normal and endoscopy and radiographic evidences are absent. We hereby report a case who presented with a history of intermittent watery diarrhea associated with occasional low-grade fever that spanned over about five years and was finally diagnosed as a case of collagenous colitis.

Keywords: Collagenous colitis; Collagenase; Matrix proteins; Colonic biopsies; Transverse colon.