BackgroundAn inosine triphosphatase (ITPA) single-nucleotide polymorphism (SNP) is associated with anemia induced by pegylated interferon and ribavirin (RBV) combination therapy in patients with chronic hepatitis C (CHC). However, there are very few reports on the hematological effects of RBV monotherapy. Here, hematological changes were monitored in patients with CHC who received RBV monotherapy, and the mechanism of these changes was investigated.MethodsPatients with CHC (n = 30) received RBV monotherapy for 4 weeks. The RBV dose was determined on the basis of body weight. Complete blood count, and serum erythropoietin (EPO) and thrombopoietin (TPO) levels were assessed. The associations between these parameters and the ITPA SNP (rs1127354) were analyzed.ResultsOver the 4 weeks, the median hemoglobin level of all patients decreased significantly, from 13.6 (10.5–16.6) to 11.7 (9.4–14.9) g/dl (P < 0.001), and the platelet counts increased, from 14.0 × 104 (8.9–37.4 × 104) to 15.8 × 104 (10.2–40.6 × 104) /mm3 (P = 0.003). At week 4, hemoglobin levels differed between patients with the ITPA CC genotype and those with the AA or AC genotypes [11.1 (9.4–13.5) vs. 12.9 (12.5–14.9) g/dl, P = 0.001]. The platelet change ratio (i.e., platelet count at week 4/platelet count at baseline) in the patients with developing anemia was correlated with the increase in the serum EPO level over 4 weeks (r = 0.88, P = 0.002), but not with the increase in the serum TPO level over 4 weeks.ConclusionsRBV monotherapy induced anemia and affected thrombocytosis in patients with CHC. Elevated endogenous EPO may stimulate platelet production.