Editor’s note: Pending an FDA decision, 23andMe no longer offers new customers access to health reports referred to in this post. Customers who purchased prior to November 22, 2013 will still be able to see their health reports, but those who purchased after that time will not. Those customers will have access to ancestry information as well as access to their uninterpreted raw data.Imagine if the simple act of eating triggered your immune system to mistakenly mount an attack inside your own body. Nearly three million people with Crohn’s or celiac disease face this distinct possibility every day in the United States, and they quickly learn that specific foods lead to a debilitating reaction. But while the two diseases share some similarities — both are autoimmune conditions localized to the digestive system — they also have many differences. For example, celiac disease is confined to the small intestine and is specifically a reaction to ingested gluten, while Crohn’s disease can occur anywhere in the digestive tract when an overactive immune system attacks “friendly” bacteria in the gut that normally help us to break down what we eat.Despite these differences, evidence suggests that the two diseases may share some of the same risk factors and underlying causes. The two diseases sometimes run in families, and Crohn’s disease — which is usually quite rare — may be more common in individuals who have celiac disease. Variants near two genes, PTPN2 and IL18RAP, have already been identified as genetic factors shared between the two diseases, but researchers believe there to be more.Recently, an international team of scientists led by Eleonora Festen of the University of Groningen in The Netherlands and Phillippe Goyette of the University of Montreal set out to uncover additional genetic risk factors contributing to both celiac disease and Crohn’s in nearly 10,000 subjects with either disease and more than 10,000 healthy individuals, all of European ancestry. Their results, published last month in PLoS Genetics, confirmed the shared associations at PTPN2 and IL18RAP and identified two other shared risk variants near the PUS10 and TAGAP genes. The CC genotypes at both and were associated with slightly higher odds of either disease compared to the CT genotype, and the TT genotypes at both SNPs were associated with slightly lower odds.(23andMe customers can view their results for and using the Browse Raw Data feature.)Variants near PUS10 have previously been shown to be associated with Crohn’s disease, as well as with celiac disease and ulcerative colitis, another bowel disorder; however, different factors seem to connect the three diseases to one another, suggesting that different variants near this gene may have different effects on disease development. The TAGAP gene was previously only associated with celiac disease, but it is thought to play a role in the immune system, making its newly identified link to Crohn’s disease more plausible. Future research may incorporate these results into elucidating the shared biological basis of these two diseases.SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.
SNPwatch: Researchers Identify Risk Variants Shared by Crohn’s Disease and Celiac Disease
February 8, 2011