In previous studies, ITPA 94 C>A (rs1127354) was known as a high risk factor for ribavirin induced toxicity in patients with chronic hepatitis C. In this recent GWAS study, Tanaka et al. revealed that SNPs on DDRGK1 and ITPA both had strong associations with hematologic toxicity in response to pegylated interferon and ribavirin therapy for chronic hepatitis C. DDRGK1 (DDRGK domain-containing protein 1) is a novel C53/LZAP-interacting protein. This evidence concerns the gene ITPA and chronic hepatitis C virus infection.