DefinitionCrohn's disease is a form of inflammatory bowel disease (IBD). It usually affects the intestines, but may occur anywhere from the mouth to the end of the rectum (anus).See also: Ulcerative colitisAlternative NamesInflammatory bowel disease - Crohn's disease; Regional enteritis; Ileitis; Granulomatous ileocolitis; IBD- Crohn's diseaseCauses, incidence, and risk factorsWhile the exact cause of Crohn's disease is unknown, the condition is linked to a problem with the body's immune system response.Normally, the immune system helps protect the body, but with Crohn's disease the immune system can't tell the difference between normal body tissue and foreign substances. The result is an overactive immune response that leads to chronic inflammation. This is called an autoimmune disorder.P