Natural YMDD-motif mutants affect clinical course of lamivudine in chronic hepatitis B.

AIM To investigate the prevalence of nature tyrosine-methionine-aspartic acid-aspartic acid motif mutations in chronic hepatitis B (CHB) patients and to evaluate the efficacy of lamivudine. METHODS A total of 1268 CHB patients were recruited from the outpatient and inpatient departments of six centers. Tyrosine-methionine-aspartic acid-aspartic acid (YMDD) mutations were analyzed using the hepatitis B virus (HBV) drug resistance line probe assay. Forty voluntary patients were selected from those with positive or negative natural YMDD mutations to undergo treatment with lamivudine. RESULTS YMDD mutations were detected in 288 (22.71%) of the 1268 CHB patients. Multivariate analysis revealed that the patients' HBV DNA level (P=0.0282) and hepatitis B e antigen status (P=0.0133) were also associated with natural YMDD mutations. The rates of normalization of alanine aminotransferase levels and HBV DNA nondetection at 6, 24, 36, and 48 wk were compared between the patients with natural YMDD mutations and those without, and the differences were not significant. However, there was a significant difference in the cumulative emergence rates of virological breakthrough at 48 wk in the patients with natural YMDD mutations and those without (32.5% vs 12.5%, P=0.032). CONCLUSION Naturally occurring YMDD mutations are detectable in a large proportion of CHB patients; breakthrough hepatitis tended to occur in patients with natural YMDD mutations.