Crohn’s disease (CD) is an inflammatory bowel disease that causes chronic inflammation and ulceration within the digestive tract. Ulcers (open sores) in the intestinal lining and inflamed tissue may swell, redden and bleed, often leading to bloody diarrhea, abdominal pain and cramping.

Irritation caused by CD can run deep – into all layers of a person’s gastrointestinal lining. Inflammation may be confined to one location or it may occur in patches, with normal tissue located between inflamed areas.

About 500,000 Americans have CD, according to the Crohn’s & Colitis Foundation of America (CCFA). Another 500,000 have ulcerative colitis, the other major type of inflammatory bowel disease. CD most often occurs in young people between the ages of 15 and 35, but may also affect older or younger populations. According to the CCFA, approximately 100,000 of those diagnosed with CD are children under 18.

The cause of CD is unknown. However, recent research indicates that the disease may result from a missing gene or the mutation of a specific gene. 

CD appears to involve dysfunction of the immune system. Protective cells normally present in the gastrointestinal lining are triggered to attack when bacteria and viruses pass through the digestive tract. In patients with CD, this attack continues, even when harmful substances are no longer present – leading to chronic inflammation and irritation. It is not clear whether this immune dysfunction is a cause or result of CD.

CD may cause inflammation and ulceration anywhere in the digestive tract. As food is digested, it enters the mouth and travels through the esophagus, stomach, small intestine and large intestine, before being expelled as waste through the anus. CD most commonly occurs in the intestines – specifically, in the ileum (last part of the small intestine) and the cecum (first part of the large intestine).