Polymyositis in patients taking antiviral clevudine therapy: a report of two cases.

The new antivirals clevudine, telbivudine and emtricitabine may be potent agents for the treatment of hepatitis B virus (HBV). However, there have been no reports on serious adverse events associated with the use of clevudine. A son and his mother both had HBV infection (ages: 27 and 47 years, respectively), and they had received antivirus treatment with clevudine (30 mg daily). They developed progressive weakness of the lower extremities and difficulty arising from the ground. Both the patients had symptoms for the previous 3 approximately 4 months in process of 14 approximately 17 months of clevudine therapy. The physical examinations showed positive Gower's sign, a decreased gait velocity and symmetrical proximal weakness (MRC grade 4/5). Their blood tests at admission revealed elevated or positive HBs Ag, HBV DNA, AST, ALT, creatine kinase, LDH, myoglobin and CK-MB. For both patients, the electrodiagnostic studies indicated myopathy and the pathologic findings of biopsied muscles revealed myositis. Drug-induced polymyositis was suspected and the clevudine was finally withdrawn. The muscle weakness and laboratory findings were improved for both patients after conservative care. We report here on the first cases of polymyositis that may have been caused by administering the new nucleoside analog clevudine for treating HBV infection.