Pathogenesis and clinical approach to extraintestinal manifestations of inflammatory bowel disease.

Crohn's disease (CD) and ulcerative colitis (UC), both should be considered as systemic diseases as they are associated with clinical manifestations involving the organs outside the alimentary tract. In a genetically susceptible host with inflammatory bowel disease (IBD), complex interaction of bacterial or other local factors in the colon with antigen presenting cells may trigger an immune reaction to a shared antigen in the involved organs. These extraintestinal manifestations (EIM) are observed in up to 20-40% of the patients with IBD. Patients with CD are more susceptible to EIMs than patients with UC. Joints, eyes, skin and biliary tract are the most commonly involved organ systems. Some manifestations such as uveitis, episcleritis may precede the onset bowel disease and some may occur in conjunction with or subsequent to the diagnosis of active bowel disease. Although many EIMs tend to follow the clinical course of IBD and respond to the treatment of underlying bowel disease, some EIMs such as primary sclerosing cholangitis and ankylosing spondylitis tend to follow a course independent of the bowel disease activity. Biological agents, particularly anti-TNFa based therapies now assume an important role in the treatment of EIMs. Early recognition and treatment of EIMs are crucial in preventing major morbidity.