Crohn's disease

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Anorectal fistulas	Clubbing	Crohn's disease, X-ray	Crohn's disease - affected areas
Digestive system	Digestive system organs	Inflammatory bowel disease	Inflammatory bowel disease - series
Ulcerative colitis

Crohn's disease is a form of inflammatory bowel disease (IBD), which involves ongoing (chronic) inflammation of the gastrointestinal tract. Crohn's-related inflammation usually affects the intestines, but may occur anywhere from the mouth to the anus (the end of the rectum).

See also: Ulcerative colitis

Inflammatory bowel disease - Crohn's disease; Regional enteritis; Ileitis; Granulomatous ileocolitis

While the exact chain of events that lead to 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 from harmful substances. But in patients with Crohn's disease and other types of inflammatory bowel disease (IBD), the immune system can't tell the difference between good substances and foreign invaders. The result is an overactive immune response that leads to chronic inflammation. This is called an autoimmune disorder.

There are five different types of Crohn's disease:

• Ileocolitis is the most common form. It affects the lowest part of the small intestine (ileum) and the large intestine (colon).
• Ileitis affects the ileum.
• Gastroduodenal Crohn's disease causes inflammation in the stomach and first part of the small intestine, called the duodenum.
• Jejunoileitis causes spotty patches of inflammation in the top half of the small intestine (jejunum).
• Crohn's (granulomatous) colitis only affects the large intestine.

A person's genes and environmental factors seem to play a role in the development of Crohn's disease.

The inflammation related to Crohn's disease frequently occurs at the end of the small intestine that joins the large intestine, but it may occur in any area of the digestive tract. There can be healthy patches of tissue in between diseases areas. The ongoing inflammation causes the intestinal wall to become thick.

The disease may occur at any age, but it usually occurs in persons between ages 15 and 35. Risk factors include a family history of Crohn's disease, Jewish ancestry, and smoking.

Review Date: 03/06/2007
Reviewed By: Updated by: A.D.A.M. Editorial Team: Greg Juhn, M.T.P.W., David R. Eltz, Kelli A. Stacy. Previously reviewed by Jenifer K. Lehrer, MD, Department of Gastroenterology, Frankford-TorresdaleHospital, Jefferson Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network.(2006)