Walker et al. (27) reported that 9.5% of non-Finnish European patients with IBD with thiopurine-induced myelotoxicity had NUDT15 variants, with the majority having p.Gly17_Val18del (NUDT15 c.37_42delGGAGTC) variant (19/35) (27). Here, NUDT15 is linked to inflammatory bowel disease.