PTPN22 and type 1 diabetes mellitus: ,2 Interestingly, several genes, such as PTPN22, IL2RA, IL18RAP, IL27, and BACH2, have been shown to be highly susceptible in, and shared between, Crohn's disease and T1D.2, 3, 4, 5 Considering the genome-based association between Crohn's disease and T1D identified by GWAS, we have verified a potential epidemiological correlation between these 2 diseases in the real world by conducting a nationwide population-based study in Taiwan that included data for 1,000,000 randomly selected people from the 16-year National Health Insurance Research Database (NHIRD) obtained from 1997 to 2013.