Microscopic colitis: Collagenous colitis and lymphocytic colitis

Collagenous colitis and lymphocytic colitis are chronic relapsing diarrheal illnesses, which are often referred to together as microscopic colitis. It most commonly occurs in women in their fifth to sixth decade. The symptoms usually include profuse watery diarrhea and crampy abdominal pain. Laboratory and endoscopic studies are generally normal but microscopic inflammation is seen when colonic biopsies are performed. In collagenous colitis there is a subepithelial collagen band in addition to chronic inflammation in the lamina propria. The etiology is not known but multiple theories exist including autoimmune, infectious, and medication-induced. Although the course is generally benign, patients may have multiple relapses over many years. Treatment regimens vary and have included anti-diarrheals, antibiotics, 5-aminosalicylates, steroids, and immunosuppressive agents.