Although a meta-analysis of 14 published studies, involving 2276 patients with IBD, showed an association between the TPMT polymorphism and AZA-induced myelosuppression in Caucasians (p < 0.00001; pooled OR, 6.97; 95% CI, 3.89–12.47), no significant correlation was found in Asians (p = 0.12) (Liu et al., 2015). This evidence concerns the gene TPMT and inflammatory bowel disease.