Crohn's disease causes inflammation of the digestive system. It is one of a group of diseases called inflammatory bowel disease. Crohn's can affect any area from the mouth to the anus. It often affects the lower part of the small intestine called the ileum.

The cause of Crohn's disease is unknown. It may be due to an abnormal reaction by the body's immune system. It also seems to run in some families. It most commonly starts between the ages of 13 and 30.

The most common symptoms are pain in the abdomen and diarrhea. Other symptoms include

• Bleeding from the rectum
• Weight loss
• Fever

Your doctor will diagnose Crohn's disease with a physical exam, lab tests, imaging tests, and a colonoscopy.

Crohn's can cause complications, such as intestinal blockages, ulcers in the intestine, and problems getting enough nutrients. People with Crohn's can also have joint pain and skin problems. Children with the disease may have growth problems.

There is no cure for Crohn's. Treatment can help control symptoms, and may include medicines, nutrition supplements, and/or surgery. Some people have long periods of remission, when they are free of symptoms.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases