Crohn's disease usually affects the lower part of the small intestine, which is called the ileum. The disease, though, can occur in any part of the gastrointestinal system. Thus, the disorder may affect the large or small intestine, the stomach, the esophagus, or even the mouth. Crohn's can occur at any age. It is most commonly diagnosed in people who are between the ages of 15 and 30.
Other symptoms can develop, depending on complications related to the disease. For example, a person with a fistula, an abnormal passageway, in the rectal area may have pain and discharge around the rectum. Other complications from Crohn's disease include:
The cause of Crohn's disease is not known. It is likely that there is a genetic component. About 20% of people with Crohn's disease have a blood relative with a form of IBD. People of Jewish heritage have a greater risk of developing Crohn's.
Crohn's disease may involve the immune system. The immune system of a person with Crohn's may treat bacteria, food, and other substances as foreign invaders, leading to chronic inflammation from the accumulation of white blood cells in the lining of the intestines and resulting in ulcerations and injury to the tissues.