First evidence for strong epistasis between two Crohn's disease susceptibility loci: PTGER4-expression-modulating polymorphisms in the 5p13.1 region enhance ATG16L1-associated susceptibility to Crohn's disease

Background and Aims: Recently, genome-wide association studies identified a number of novel susceptibility loci for Crohn's disease (CD) including a 250 kb region on chromosome 5p13.1, which modulates PTGER4 expression (PLoS Genet 2007;3:e58). We aimed to replicate this association in a large German cohort of patients with inflammatory bowel disease (IBD) and to elucidate potential genotypic and phenotypic interactions with other IBD genes.