Crohn's disease is a chronic inflammatory process involving the intestinal tract anywhere from the mouth to the anus. The most commonly affected areas of the intestinal tract are the last part of the small intestine (ileum), large intestine (colon and rectum) and the anus.
Any age group may be affected, but the majority of patients are young adults between 16 and 40 years old. Crohn's disease occurs most commonly in people living in northern climates. It affects men and women equally and appears to be common in some families. About 20% of people with Crohn's disease have a relative, most often a brother or sister, and sometimes a parent or child, with some form of inflammatory bowel disease; however there is no clear pattern for how this disease is passed down to other relatives. The exact cause of this disease is not known; however, current theories consider an immunologic (the body's defense system) and/or bacteria-mediated cause.