A Case of Fatal Hepatitis B Virus Reactivation During Prophylactic Entecavir Prescription

A male patient in his sixties underwent rituximab-based chemotherapy for B-cell lymphoma. Given his hepatitis B virus (HBV) surface antigen positivity, he was prescribed prophylactic entecavir therapy during and after chemotherapy. One month following the completion of treatment, serum HBV-DNA became detectable again; however, this early sign of reactivation went unrecognized, ultimately resulting in acute liver failure. The patient died three months after completing chemotherapy. Most reactivated HBV strains do not carry mutations associated with entecavir resistance. Although drug adherence could not be confirmed due to the patient's comatose state, non-adherence to entecavir therapy was strongly suspected to be the cause of HBV reactivation. This case underscores the critical importance of consistent HBV-DNA monitoring and strict adherence to prophylactic therapy to prevent HBV reactivation.