Extraintestinal Manifestations of Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) are complex inflammatory disorders of the gastrointestinal tract which could involve multiple organ systems and present with various extraintestinal manifestations. Almost every organ system may be affected in IBD including the musculoskeletal system, skin, eyes, liver, lungs, kidneys, immune system, hematologic system, and cardiovascular system. Certain extraintestinal manifestations are frequently related to the activity of the IBD (peripheral arthritis, oral ulcers, erythema nodosum, episcleritis), while others develop independently of the intestinal inflammation (axial arthropathies, hepatobiliary disorders). The etiopathogenesis of IBD is complex and includes interaction between environmental factors and immune system in genetically susceptible individuals. Autoinflammation is becoming increasingly recognized as an important component in the pathogenesis of IBD, especially Crohn’s disease. Genetic loci specifically associated with Crohn’s disease consistently implicate involvement of innate immunity (CARD15/NOD2, IRGM, IL23R, LRRK2, and ATG16L1) and de-regulated adaptive immune responses, namely, the interleukin-23 and T helper 17 cell pathways. This chapter provides comprehensive review of various extraintestinal manifestations associated with IBD with specific focus on autoinflammation.