Ulcerative colitis causes ulceration and inflammation of the inner lining of the colon and rectum, while Crohn's disease is an inflammation that extends into the deeper layers of the intestinal wall. The correct diagnosis may take some time. In other cases, only the colon is involved. Sometimes, inflammation also may affect the mouth, esophagus, stomach, duodenum, appendix, or anus. Crohn's disease is a chronic condition and may recur at various times over a lifetime.
Some people have long periods of remission, sometimes for years, when they are free of symptoms.
There is no way to predict when a remission may occur or when symptoms will return. The most common symptoms of Crohn's disease are abdominal pain, often in the lower right area, and diarrhea. There also may be rectal bleeding, weight loss, and fever. Children may suffer delayed development and stunted growth. There are many theories about what causes Crohn's disease, but none has been proven.