Crohn’s disease and ulcerative colitis are two forms of inflammatory bowel disease (IBD) that affect more than 2.5 million people of European ancestry, with rising prevalence in other populations. Both result in many of the same gastrointestinal symptoms and are potentially due to an improper response of the body’s immune system to harmless cells or bacteria.
The new study, led by Professor Judy Cho at the Yale School of Medicine in the US, identified 71 new genetic associations for IBD, many of which have been previously linked to other immune-related disorders.
Patients from around Australia and New Zealand contributed to the project through the Australian New Zealand IBD consortium. Professor Ian Lawrance, from The University of Western Australia’s School of Medicine and Pharmacology, also used data from patients at Fremantle Hospital to contribute to the project.
“The findings are a step to unravelling the question of how the gut’s immune system and the intestinal luminal microflora interact and provide clues to better understand what causes these complex inflammatory diseases,” Professor Lawrance said.
The current most effective treatments may control inflammation but the downside is an increased risk of infection, particularly reactivation of tuberculosis (TB). This study observed that there was a striking overlap between the genetics predisposing to IBD and the body’s ability to respond to mycobacterial infection, the organism that causes TB.
The International IBD Genetics Consortium, a network of researchers including Professor Lawrance, is working on the genetics of IBD and has undertaken many genome-wide association studies and meta-analyses of Crohn’s disease and ulcerative colitis as separate traits.
According to the US news research website Science Daily, co-author Ramnik Xavier, Chief of Gastroenterology and Director of the Center for the Study of Inflammatory Bowel Disease at Massachusetts General Hospital, said there had been a paradigm shift in researchers’ understanding of IBD.
“This gene discovery process offers an opportunity to begin identifying new targets for treatment, better diagnostic tools, and in the long-term, personalised care for patients,” he said.
“We now have the necessary starting material to understand the pathways that contribute to Crohn’s disease and ulcerative colitis, and we also have a framework to better appreciate that they may not be two distinct diseases, but rather collections of many different diseases.”
The paper “Host-microbe interactions have shaped the genetic architecture of inflammatory bowel disease” was published last week in Nature.