Lymphocytic colitis, a subtype of microscopic colitis, is a rare conition characterized by chronic non-bloody watery diarrhea. The colonoscopy is normal but the mucosal biopsy reveals an accumulation of lymphocytes in the colonic epithelium and connective tissue (lamina propria). Collagenous colitis shares this feature but additionally shows a distinctive thickening of the subepithelial collagen table. The peak incidence of lymphocytic colitis is in persons over age 50; the disease affects women more than men.