Microscopic colitis with granulomatous inflammation

AIMS: To present four cases in which the clinical and endoscopic findings were consistent with microscopic colitis, but the inflammatory infiltrate included a conspicuous granulomatous reaction. Microscopic colitis is defined as a syndrome of chronic watery diarrhoea with a chronic inflammatory cell infiltrate in the colonic mucosa and without significant abnormalities at colonoscopy. It encompasses both collagenous and lymphocytic colitis. METHODS AND RESULTS: In all cases the clinical course and endoscopic findings were unlike Crohn's disease and no infectious agents were identified. In all cases the main symptom was frequent watery diarrhoea, all were female and there were no endoscopic findings apart from mild mucosal erythema. Histologically, an active chronic inflammatory infiltrate was accompanied by scattered non-necrotizing granulomas, often closely associated with crypt epithelium (cryptolytic or pericryptal granulomas). In three of the patients the symptoms began after antibiotic use or had worsened with antibiotic use. Two of the patients were on allopurinol at the time of the onset of symptoms. In two of the patients symptoms have continued for more than 10 years. One patient died as a result of medical complications relating to severe diarrhoea and dehydration. CONCLUSIONS: Microscopic colitis rarely may be characterized by granulomatous inflammation. Such patients should not be regarded as having Crohn's disease.