Early emergence of entecavir‐resistant hepatitis B virus in a patient with hepatitis B virus/human immunodeficiency virus coinfection

The efficacy of entecavir for patients with hepatitis B virus/human immunodeficiency virus coinfection has not been fully elucidated. Here we examined a patient coinfected with both viruses in whom entecavir‐resistant hepatitis B virus appeared. The 60‐year‐old Japanese male with the coinfection received antiretroviral therapy including lamivudine. The therapy initially suppressed replication of both viruses, followed by reactivation of the hepatitis B virus alone by 2 years of therapy. He subsequently received entecavir therapy in addition to the antiretroviral regimen. After entecavir administration, the hepatitis B virus DNA level was slightly reduced, but then increased after 6 months of entecavir therapy. In the sequencing analysis of hepatitis B virus, no drug resistance‐associated amino acid substitutions were observed in the reverse transcriptase (rt) domain before antiretroviral therapy. The lamivudine‐resistant amino acid substitutions at rt173, rt180 and rt204 were detected before entecavir administration, and further the entecavir‐resistant rt202 substitution was observed after 6 months of entecavir therapy. The full‐length hepatitis B sequences showed that the viral strain derived from the patient belonged to genotype H. In summary, this report describes a patient with hepatitis B virus/human immunodeficiency virus coinfection who received entecavir therapy in addition to an antiretroviral regimen and showed the early emergence of entecavir‐resistance hepatitis B virus. In entecavir therapy for patients infected with both viruses, great care should be taken with respect to the emergence of entecavir‐resistant hepatitis B virus, especially in patients with pre‐existing lamivudine‐resistant virus.