More than 30 genetic loci have been identified that confer susceptibility to Crohn’s disease, a common inflammatory bowel disorder, according to a study published online this week in Nature Genetics. This is the most complete picture yet assembled of the genetic influences on risk of a common disease.
Three genome-wide scans for Crohn’s disease have recently been published, revealing 11 loci that lead to increased risk of the disease. Led by Mark Daly, the authors of those studies have now combined their data and conducted an overall ‘meta-analysis’, which increases the likelihood of identifying variants with modest effects on disease susceptibility. With this approach an additional 21 loci were found. Together, these 32 loci account for approximately 10% of the overall variance in disease risk, which may reflect as much as 20% of the genetic risk, given a substantial role for environmental factors. The overall picture suggests that there are a small number of loci that confer significant added risk, and a much larger number with smaller effects.
Three of the individual genes that have been implicated in Crohn’s disease have previously been shown to influence risk of type 1 diabetes and asthma, raising the possibility of common genetic mechanisms underlying these disorders.