Microscopic colitis: lymphocytic and collagenous colitis

Abstract Microscopic colitis is a type of inflammatory bowel disease comprising at least two entities, lymphocytic colitis and collagenous colitis. Since its recognition in 1976 it has been diagnosed with increasing frequency. However, it is still commonly overlooked or misdiagnosed by clinicians and histopathologists alike. In this review the terminology of microscopic colitis is clarified and the diagnostic features are described. Differential diagnoses and diagnostic pitfalls are discussed and newer potentially useful adjunctive techniques are described. Finally, recent advances in the understanding of the pathogenesis of these conditions are summarized.