Severe thrombocytopenia in a patient with inosine triphosphatase (ITPA)–CC genotype caused by pegylated interferon (IFN)-α-2a with ribavirin therapy: a case report

BACKGROUND: Pegylated interferon combined with ribavirin treatment is an effective therapy for chronic hepatitis C viral infection. However, pegylated interferon combined with ribavirin is associated with various adverse reactions. Severe thrombocytopenia is a life-threatening side effect of interferon therapy that can lead to bleeding. It is generally understood that the inosine triphosphatase-CC genotype does not have a significantly lower reduction by pegylated interferon combined with ribavirin in the mean platelet counts compared with the AA/CA genotype. We report a case of severe thrombocytopenia that developed in a patient with chronic hepatitis C treated with pegylated interferon combined with ribavirin in spite of having the inosine triphosphatase-CC genotype. CASE PRESENTATION: A 57-year-old female had been diagnosed as having HCV infection in 2008. The inosine triphosphatase gene showed one single nucleotide polymorphism (rs1127354) C/C (major homozygous) and the IL28B gene showed single nucleotide polymorphism (rs8099917 T/T, rs11881222 T/T) (major homozygous). The patient was treated with pegylated interferon 180 μg once a week combined with ribavirin 600 mg per day from April 2011. The hepatitis c virus ribonucleic acid turned negative 9 weeks after treatment with pegylated interferon combined with ribavirin. During the therapy, the platelet count remained above 8.0 × 10(4)/μl for about 9 months. In January 2012, the platelet count was 6.8 × 10(4)/μl. In February 2012, the 44th week from the beginning of the treatment, a sudden decrease in the platelet count to 0.8 × 10(4)/μl was observed. After prednisolone was administered, the platelet count increased. Finally the platelet count had risen above normal range. CONCLUSION: We should pay careful attention in the differential diagnosis for patients with the inosine triphosphatase-CC genotype because, although rare, severe thrombocytopenia could occur.