Independent studies have associated NUDT15 gene variant (rs116855232, R139C) with intolerance to a thiopurine treatment (such as 6-mercaptopurine, azathiopurine, or 6-thioguanine (Karran and Attard 2008) and with thiopurine-induced adverse drug reactions in patients with acute lymphoblastic leukemia (ALL) and inflammatory bowel disease (IBD) (Yang SK et al. 2014; Yang et al. 2015). The gene discussed is NUDT15; the disease is inflammatory bowel disease.