Our PRS results were not driven by the few loci known to be associated with age-at-diagnosis of IBD (NOD2, HLA, and MST1)27 and similar findings were obtained when restricting the CD polygenic burden test to VEO-IBD cases defined in the COLORS cohort as CD or CD plus undeterminable IBD (IBDu), and when restricting the UC polygenic burden test to VEO-IBD cases defined as UC or UC plus IBDu (Supplementary Fig. 10). This evidence concerns the gene MST1 and inflammatory bowel disease.