Inflammatory bowel disease (IBD), encompassing Crohn's disease (CD) and ulcerative colitis (UC), is a chronic inflammatory disease of the gastrointestinal tract driven by an inappropriate and continuing inflammatory response in a genetically susceptible host [1]. Early evidence from twin studies showed that the concordance rate in monozygotic twins with CD and UC was 30–35 % and 10–15 %, respectively, supporting a role for genetics in the risk of IBD [1]. Recent advancements in our understanding of IBD have identified specific genes and genetic loci associated with susceptibility, quantified by polygenic risk scores (PRS) [2,3]