Hepatitis B virus (HBV) reactivation from resolved infection is a serious problem which can frequently lead to severe hepatitis. Generally, it occurs several months after the start of immunosuppressive therapy; however, it sometimes occurs a few years later, even after cessation of therapy. Here we report a patient with de novo HBV infection who had received corticosteroid therapy for pemphigus vulgaris for 6 years. Full-genome HBV sequence analysis using serial serum samples revealed that the patient was infected with HBV subgenotype C2, which had the G1896R mixed mutation in the precore region. Interestingly, it had the immune escape mutations P120A and G145R in the S gene. Because both hepatitis B surface antigen and antibodies to hepatitis B surface antigen (HBsAb) were positive at the onset of the de novo infection, it was considered that HBV with these mutations escaped from neutralization by the pre-existing HBsAbs. This case indicates that HBV reactivation with an immune escape mutant can occur long after immunosuppressive therapy.
Keywords: G145R; HBV; Immunosuppression; P120A; Pemphigus vulgaris.