A moderately severe chronic inflammation of the intestine, especially of the small intestine, of unknown cause, involving the obstruction of the lower part of the small bowel and less frequently other parts of the gastrointestinal tract. It is characterized by patchy deep ulcers that may cause abnormal passages within the bowel, and narrowing and thickening of the bowel. Symptoms include fever, diarrhea, cramping abdominal pain, and weight loss.

Crohn’s disease usually involves the small intestine, most often the lower part (the ileum). In some cases, both the small and large intestine (colon or bowel) are affected. 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.