The three most common sites of intestinal involvement in Crohn's disease (left) compared to the areas affected by ulcerative colitis (colitis ulcerosa, right)
Although the precise causes of Crohn's disease (CD) are unknown, it is believed to be caused by a combination of environmental, immune, and bacterial factors in genetically susceptible individuals.[3][13][14][15] It results in a chronic inflammatory disorder, in which the body's immune system defends the gastrointestinal tract, possibly targeting microbialantigens.[14][16] While Crohn's is an immune-related disease, it does not seem to be an autoimmune disease (the immune system is not triggered by the body itself).[17] The exact underlying immune problem is not clear; however, it may be an immunodeficiency state.[16][18][19]
About half of the overall risk is related to genetics, with more than 70 genes involved.[1][20] Tobacco smokers are three times as likely to develop Crohn's disease as non-smokers.[6] It often begins after gastroenteritis.[1] Other conditions with similar symptoms include irritable bowel syndrome and Behçet's disease.[1]
There is no known cure for Crohn's disease.[1][3]Treatment options are intended to help with symptoms, maintain remission, and prevent relapse.[1] In those newly diagnosed, a corticosteroid may be used for a brief period of time to improve symptoms rapidly, alongside another medication such as either methotrexate or a thiopurine used to prevent recurrence.[1] Cessation of smoking is recommended for people with Crohn's disease.[1] One in five people with the disease is admitted to the hospital each year, and half of those with the disease will require surgery at some time during a ten-year period.[1] While surgery should be used as little as possible, it is necessary to address some abscesses, certain bowel obstructions, and cancers.[1] Checking for bowel cancer via colonoscopy is recommended every few years, starting eight years after the disease has begun.[1]
Crohn's disease affects about 3.2 per 1,000 people in Europe and North America;[12] it is less common in Asia and Africa.[21][22] It has historically been more common in the developed world.[23] Rates have, however, been increasing, particularly in the developing world, since the 1970s.[22][23] Inflammatory bowel disease resulted in 47,400 deaths in 2015,[24] and those with Crohn's disease have a slightly reduced life expectancy.[1] It tends to start in adolescence and young adulthood, though it can occur at any age.[25][1][3][26] Males and females are equally affected.[3]
^ abCosnes J (June 2004). "Tobacco and IBD: relevance in the understanding of disease mechanisms and clinical practice". Best Practice & Research. Clinical Gastroenterology. 18 (3): 481–496. doi:10.1016/j.bpg.2003.12.003. PMID15157822.
^Frisch M, Gridley G (October 2002). "Appendectomy in adulthood and the risk of inflammatory bowel diseases". Scand J Gastroenterol. 37 (10): 1175–7. doi:10.1080/003655202760373380. PMID12408522.
^ abDessein R, Chamaillard M, Danese S (September 2008). "Innate immunity in Crohn's disease: the reverse side of the medal". Journal of Clinical Gastroenterology. 42 (Suppl 3 Pt 1): S144–7. doi:10.1097/MCG.0b013e3181662c90. PMID18806708.
^Stefanelli T, Malesci A, Repici A, Vetrano S, Danese S (May 2008). "New insights into inflammatory bowel disease pathophysiology: paving the way for novel therapeutic targets". Current Drug Targets. 9 (5): 413–8. doi:10.2174/138945008784221170. PMID18473770.
^Lalande JD, Behr MA (July 2010). "Mycobacteria in Crohn's disease: how innate immune deficiency may result in chronic inflammation". Expert Review of Clinical Immunology. 6 (4): 633–641. doi:10.1586/eci.10.29. PMID20594136. S2CID25402952.