A 74-year-old woman with Sjögren's syndrome and chronic hepatitis C (CHC) was admitted to our hospital in October 2003 for treatment of diabetes mellitus. She had the past history of recurrent thrombocytopenia, which was proven to be due to peripheral destruction. Although she had been diagnosed with hypertrophic cardiomyopathy (HCM) for 2 years, she had never felt palpitation. She suddenly died probably of fatal arrhythmia related to HCM during the last hospitalization. Although hepatitis C virus (HCV) infection has been associated with Sjögren's syndrome, thrombocytopenia, HCM, and diabetes mellitus, all these diseases rarely occur in a single patient. It will be necessary to identify similar cases to elucidate the etiopathogenesis of extra-hepatic manifestations of HCV infection.