Granulomatous Microscopic Colitis Due to Allopurinol

This document reported a rare case of granulomatous microscopic colitis in a 77-year-old male, potentially linked to allopurinol use. The patient presented with explosive diarrhea and tenesmus for 10 months. Colonoscopy revealed subtle vascular changes, and biopsies showed diffuse mucosal inflammation with lymphocytes and well-formed epithelioid granulomas. The patient was treated with budesonide, leading to symptom resolution. The presence of granulomas was unusual for microscopic colitis, suggesting a possible drug reaction to allopurinol, although the medication was not discontinued due to the patient's positive response to treatment.