In one of the largest studies of its kind, researchers have identified 71 genetic regions newly associated with inflammatory bowel disease (IBD), increasing the total number discovered to date to 163. This new information reveals that there is a vast amount of genetic overlap between Crohn’s disease and Ulcerative colitis (the two most common subtypes of IBD), suggesting that they share common biological pathways. In addition, analyzing these regions reveals that IBD may result from the body’s immune response over-reacting, the result of a long-term evolutionary balancing act between defense against bacterial infection and harmful excessive inflammation.
IBD is a group of inflammatory conditions of the colon and small intestine. About one person in every 250 people in the United Kingdom suffers from one of the major types of IBD. It is not yet known what causes this disease; an unknown factor, or a combination of factors seems to trigger the body’s immune system to produce an inflammatory reaction in the intestinal tract that continues without control. As a result of the inflammatory reaction, the intestinal wall is damaged leading to bloody diarrhoea and abdominal pain. IBD patients require lifelong treatment with dietary management and drug therapy, and often need surgery to repair the damage the disease causes.
"We have greatly expanded the map of genetic regions that are associated with IBD,” says Luke Jostins, joint first author from the Wellcome Trust Sanger Institute. "Each of these regions increases a person's chance of developing IBD by only a fraction of one per cent and even taken together they cannot tell us who will or will not develop the disease. But they each tell a small story about the biology of this disorder, and by combining them we find biological pathways that, if disrupted, can lead to IBD."