Crohn's disease is an autoimmune condition of the intestinal tract. We believe that Crohn's disease occurs due to loss of control of the immune system of our intestinal tract, which consists of all the organs involved in digestion from the mouth to the anus. In healthy individuals, the intestine routinely becomes mildly inflamed when exposed to food and bacteria, as a response to these agents and to allow your body to absorb nutrients but not become infected.

In the healthy individual, the inflammation response is then turned off and the bowel or intestinal tract returns to its resting state. When someone has food poisoning or is exposed to bacteria in the intestinal tract that cause injury, the inflammatory response of the intestinal tract may be more intense as a defense mechanism and to assist in healing, but in most cases when this occurs, the body then returns to a normal resting state.

In patients who are susceptible to Crohn's disease, we believe that some element of the environment triggers an immune response that loses control. One way to think about this is that the immune system of the gut has become "overactive" and has either lost the "off switch" or is alternatively stuck in the "on" position. Another possible explanation is that the body has lost the ability to distinguish between "self" and the environment. There are theories about Crohn's disease that suggest it is caused by infections or that there is a specific organism that is at the heart of most patients' disease. However, we currently believe that while infections may trigger the onset of the disease in some patients, it is likely more complicated than that.

To summarize, our current theory of Crohn's disease is that it is an overactive immune system in a genetically susceptible individual that is triggered by some environmental event. Those who have a greater genetic component to their disease may develop the disease at an earlier age, while those who have less of a genetic component may develop the disease after a more intense or prolonged environmental exposure.

Another strong environmental "trigger" is smoking. Patients with Crohn's disease are more often smokers of cigarettes and tobacco than those who do not have Crohn's disease. We know that patients with Crohn's disease who smoke have more aggressive disease, disease that is more difficult to treat and disease that is much more likely to return after surgery. It is, therefore, extremely important that patients who have Crohn's disease and smoke enroll in smoking cessation programs and it is important that patients with Crohn's disease who do not smoke never start. We also believe that the family members of Crohn's disease patients should avoid smoking and probably avoid anti-inflammatory medicines like Ibuprofen or prolonged use of aspirin, which we think may also trigger disease.