A multicenter study that enrolled 446 Japanese HCV genotype 2 patients (303 treatment-naïve and 143 treatment-experienced patients), including 190 (42.6%) patients aged ≥ 65 years and 90 (20.2%) patients with compensated cirrhosis, indicated that 10.5% of patients developed anemia with hemoglobin levels < 10 g/dL; being ≥65 years old and ITPA CC genotype were associated with the development of anemia. This evidence concerns the gene ITPA and anemia (phenotype).