SLC22A4 and Crohn disease: Initial reports that a gain-of-function polymorphism (L503F variant, rs1050152) in SLC22A4 that increased transport efficiency of ergothioneine was associated with increased risk of Crohn’s disease(56) were subsequently shown to have been confounded by the SLC22A4 gene being in linkage disequilibrium with the interferon regulatory factor 1 (IRF1) gene, which was the locus conferring Crohn’s disease susceptibility(57).