The Incidence and Clinical Outcome of YMDD Mutants in Hepatitis B Surface Antigen-Positive Renal Allograft Recipients After Prolonged Lamivudine Therapy

Although lamivudine (LAM) is a potent inhibitor of hepatitis B virus (HBV), prolonged therapy may induce the development of LAM-resistant strains, YMDD mutants. Although YMDD mutants have impaired replication that leads to a benign clinical course compared with wild-type virus, some immunosuppressive agents may enhance replication of YMDD mutants, causing a severe hepatitis flare. We retrospectively investigated the incidence and clinical outcomes of YMDD mutants in renal allograft recipients on immunosuppressive treatment. Clinical records of 25 renal allograft recipients, who underwent renal transplantation between December 1997 and February 2006 were hepatitis B surface antigen positive at the time of transplantation, were reviewed. All patients received LAM treatment after renal transplantation. Over 9 to 98 months of follow-up, 16 patients (64.0%) maintained undetectable HBV DNA levels; however, 9 patients (36.0%) showed persistent or increased levels of HBV DNA. Seven were identified as having developed YMDD mutants. Although genotypic analysis was not performed, YMDD mutants were strongly suspected in another two patients, who developed severe hepatic dysfunction combined with high levels of HBV viremia at close to 2 years of LAM therapy. One patient recovered after hepatic transplantation and another patient died of hepatic failure. In conclusion, the incidence of YMDD mutants was similar to that of nonimmunosuppressed individuals; however, the presence of these mutants made it more likely for severe liver disease to develop in renal transplant recipients. Therefore, close monitoring for the development of YMDD mutants should be performed during LAM treatment, especially in this group of patients.