Inflammatory bowel disease (IBD), the major example of which is Crohn's disease, involves inflammation of the intestine, especially the small intestine. Inflammation refers to swelling, redness, and loss of normal function. There is evidence that the inflammation is caused by various products of the immune system, which attack the body itself instead of helpfully attacking a foreign invader (a virus or bacteria, for example). The inflammation of Crohn's disease most commonly affects the last part of the ileum (a section of the small intestine), and often includes the large intestine (the colon). However, inflammation may also occur in other areas of the gastrointestinal tract, affecting the mouth, esophagus, or stomach. Crohn's disease differs from ulcerative colitis, the other major type of IBD, in two important ways:

• The inflammation of Crohn's disease may be discontinuous, meaning that areas of involvement in the intestine may be...