In one of the largest studies of its kind ever conducted, an international team of scientists has thrown new light on the genetic basis of the inflammatory bowel diseases (IBD). Crohn's disease and ulcerative colitis, the two most common forms of IBD, are chronic inflammatory digestive disorders affecting 230,000 Canadians. Dr. John Rioux, researcher at the Montreal Heart Institute and Associate Professor of Medicine at the Université de Montréal, is one of the researchers who have identified 71 genetic regions newly associated with inflammatory bowel disease (IBD), increasing the total number discovered to date to 163, in one of the largest studies of its kind. Also, the study points out that these regions showed a striking overlap with those implicated in autoimmune diseases and in immune deficiencies. Even more surprising was the observation of a significant overlap with genetic regions controlling our response to microbial infections such as in the case of tuberculosis. These highlights were published in the prestigious scientific journal Nature today.
Moreover, these findings suggest that IBD results from overactive immune defence systems that evolved to fight off serious bacterial infections. In IBD, the body's immune system produces an ongoing inflammatory reaction in the intestinal tract that injures the intestinal wall, leading to diarrhea and abdominal pain. IBD patients typically require lifelong treatment with drug therapy, and often need surgery to repair tissue damage caused by the disease.
Up until this point, researchers have been studying Crohn's disease and ulcerative colitis separately. This study was based on the fact that there seems to be a vast amount of genetic overlap between the two disorders.
In the first step of the study, the researchers conducted a "meta-analysis" of 15 previous genomic studies of either Crohn's disease (CD) or ulcerative colitis (UC), the two most common forms of IBD, creating a large dataset that combined genetic information from some 34,000 individuals who took part in those studies. The results then formed part of a second meta-analysis that included data from new genome-wide scans of more than 41,000 DNA samples from CD/UC patients and healthy comparison subjects collected at 11 centers around the world by the International IBD Genetics Consortium.