Extraintestinal manifestations of inflammatory bowel disease.

Inflammatory bowel disease (IBD) predominantly affects the gastrointestinal system but it is associated with a large number of extraintestinal manifestations (EIM). These extraintestinal disorders can significantly contribute to morbidity and impair the overall life quality. EIM may be diagnosed before, concurrently with, or after the diagnosis of IBD is made. The precise etiology of EIM remains unknown. It currently is believed that mucosa from the underlying bowel disease may provide associated immune responses for the inflammatory process in the extraintestinal sites. The involvement of autoimmune mechanisms has been suggested when the shared and unique epitopes in the human colon, eye, joint and biliary epithelium were detected. Recently, the presence of long-lived populations of memory lymphocytes has been discovered which arise as a consequence of bowel inflammation and express homing receptors that direct their migration not only to the gut but also to the extraintestinal sites. The most common extraintestinal disorders associated with IBD include dermatologic, ophthalmologic, musculoskeletal and hepatobiliary diseases, although virtually every organ system may be involved. If these disorders can be considered as the real extraintestinal manifestations of IBD or represent just association between different syndromes of autoimmune etiology, is still not clear. It is important to acquire knowledge on these extraintestinal manifestations of Crohn's disease and ulcerative colitis to start the respective treatment early.