A companion paper by French scientists in the same journal confirms the link in a different group of patients. We have long suspected that both genetics and the environment played a role. This finally allows us to begin to understand how they work together to cause this disease. Crohn's is a chronic inflammatory disease of the gastrointestinal tract, usually the small intestine. It affects about 500,000 people in the United States, most often before age 30, causing abdominal pain, diarrhea, fever and weight loss.
Symptoms range from mild to severe.
The cause is unknown. Although everything from diet to emotional stress has been suggested, the prevailing theory is that in patients with Crohn's disease, the intestinal immune system over-reacts to viral or bacterial agents and initiates an ongoing, uncontrolled inflammation of the intestine. Treatments are based on controlling inflammation through suppressing the immune response. The disease tends to cluster in certain families, suggesting that genes play an important role. This finding connects the disease with an arm of the immune system known as the innate immune system.