Introduction: The incidence of microscopic colitis has recently increased. Although collagenous colitis and lymphocytic colitis are the two main subtypes of microscopic colitis, many patients may not fit into either category and are thus included under the header nonspecific colitis. Of late, the spectrum of microscopic colitis has widened to include minimal change colitis, microscopic colitis not otherwise specified and microscopic colitis with giant cells. There is a lack of information concerning the spectrum of microscopic colitis in Asia.
Method: In a retrospective analysis, case records of 29 patients diagnosed with microscopic colitis between 1999-2005 were analysed. Drug use parasitic infection and common bacterial infections were excluded. Colonoscopic/ sigmoidoscopic examination was done and multiple colonic mucosal biopsies were stained serially with haematoxylin and eosin for detailed histological examination and Masson trichrome for sub-epithelial collagen band. Based on histological criteria, patients were categorised into five subtypes: collagenous colitis (presence of collagenous thickening of surface epithelium basement membrane > 10 microm), lymphocytic colitis (intra-epithelial lymphocytes more than 20 per 100 colonocytes), minimal change colitis (crypt architectural abnormality in the form of cryptitis and crypt dilatation in the absence of increase in intraepithelial lymphocytes and subepithelial collagenous band), microscopic colitis not otherwise specified (increased inflammatory cell infiltrates in the lamina propria in the absence of other abnormalities) and microscopic colitis with giant cells.
Results: Mean age of patients was 38.59 years (range 12-62). Of 29 patients with microscopic colitis, 7 (24.1%), 4 (13.8%), 7 (24.1%) and 11 (37.9%) were classified as collagenous colitis, lymphocytic colitis, minimal change colitis and microscopic colitis not otherwise specified, respectively. None of these patients had giant cells. There was no significant correlation between disease type and clinical manifestations.
Conclusion: Microscopic colitis has a wide histological spectrum. Cases reported as non-specific colitis, may be categorised into definite subtypes of microscopic colitis.