A Rare Case of Myopathy Associated with Entecavir Initiation.

Hepatitis B virus (HBV) infection can lead to severe complications, including cirrhosis, hepatocellular carcinoma, and death. Entecavir, a guanosine nucleoside analogue, is recommended for chronic hepatitis B virus (CHB) and is rarely associated with myopathy. This report presents a 65-year-old woman with CHB who developed suspected entecavir-associated myopathy. The patient, with a history of hypertension, systemic lupus erythematosus, rheumatoid arthritis, seizures, stroke, polyneuropathy, cervical and lumbar myelopathy, bilateral lumbar radiculopathy, and alcohol use, was admitted for chest pain. Acute pathologies were ruled out; however, acute reactivation of CHB was identified. Entecavir was initiated, but the patient developed significant fatigue and muscle weakness within days, in the absence of acute liver failure. On discontinuation of entecavir and initiation of tenofovir disoproxil fumarate, the patient's symptoms improved. This case highlights the rare but serious adverse effects of entecavir, emphasizing the need for careful monitoring and consideration of alternative treatments in patients with CHB.