Newly recognized forms of colitis: collagenous colitis, microscopic (lymphocytic) colitis, and lymphoid follicular proctitis

Based on pertinent data from the literature and on their personal experience, the authors present a clinicopathological review of collagenous colitis, microscopic (lymphocytic) colitis, and lymphoid follicular proctitis. The following aspects of these three newly recognized forms of colitis are emphasized: clinical features, light microscopy, histological diagnostic problems, immunological aspects, coexisting diseases, treatment, etiology, and pathogenesis. Special attention is paid to possible overlap between collagenous colitis and microscopic (lymphocytic) colitis.