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What causes ulcerative colitis?

Ulcerative colitis is predominantly a disease of the the developed world, and is uncommon in the developing world, possibly due to a higher prevalence of intestinal infections in the developing world. The exact reasons why some individuals develop ulcerative colitis are unknown, although a number of inherited and enviromental factors increase the risk of developing the disease.

It is currently believed that ulcerative colitis is caused by an inappropriate repsonse by an individials immune system to bacteria normally present in the colon. The evidence for the role of bacteria comes from the observation that animals that are susceptible to developing colitis due to genetic mutations do not develop inflammation if kept in a bacteria-free enviroment.

Although the colon normally contains over 1 billion bacteria, no single organism has been identified as the cause of ulcerative colitis. Similarly, the association between genetic mutations and ulcerative colitis is relatively weak, and thus no single genetic test for ulcerative colitis currently exists [1]. A variety of inherited deficiencies in the control of immune responses to bacteria in the colon may allow normally benign bacteria to invade the colon. Interestingly, ulcerative colitis is less common in smokers, and patients who stop smoking are at increased risk of a flare of the disease. Some speculate that nicotine or its metabolites may have protective properties in strengthening colonic defences. As the precise triggers for the disease are unclear, current treatment focuses on suppressing the immune response that has been activated.

Contact Information

Inflammatory Bowel Disease Program
Digestive Disease Center
Beth Israel Deaconess Medical Center
330 Brookline Avenue
Boston, MA 02215