The Puzzle of IBD
Scientific observations over the years have revealed tantalizing connections between IBD and other factors. In Sweden, Crohn’s disease was three times more common in people born during certain measles outbreaks than those born at other times.
Crohn’s disease occurs twice as often in smokers but, in contrast, ulcerative colitis is seen half as often in smokers. One of the other major questions about IBD is whether ulcerative colitis and Crohn’s disease are separate diseases, or are two different forms of the same disease. IBD researchers are focusing their probes on infectious agents and the body?s immune system
Researchers have tried unsuccessfully to isolate a bacterial, fungal or viral cause for IBD. Many of these organisms can produce acute colitis, but there is no evidence that any one of them in particular is involved in IBD. One of the bacteria most suspect is Mycobacterium paratuberculosis.
This bacterium has been found in some people with Crohn?s disease, and is known to cause a similar intestinal disease in cattle and other ruminants. But the bacterium is found in people who don’t have IBD, and treatment with antibiotics targeted at the bacterium has produced inconsistent results.
People with IBD also tend to have immune system abnormalities. But researchers still don’t know whether the inflammation is an appropriate response to some antigen or abnormal stimulus or an abnormal response to a normal stimulus such as bacteria commonly found in the intestine. In other words, the abnormal immune system response could be either a cause or a symptom of IBD.
Many speculate that IBD may be caused in part by an abnormal or altered immune response in the intestinal lining, perhaps triggered by common intestinal bacteria or substances usually ignored by the immune system.
The extraintestinal symptoms such as arthritis are similar to symptoms associated with autoimmune disorders.
Some of the drugs used to treat autoimmune disease, such as glucocorticoids, azathioprine and cyclosporine, are also often effective with IBD. Studies have shown that there are significant changes in the way the immune system operates in the mucosa of people with IBD. The normal balance in the immune response breaks down and goes out of control, resulting in damage to healthy tissue.