Hydatid Cyst of the Thigh With Incidental Hepatitis B: A Rare Case.

Hydatid cyst, also known as cystic echinococcosis, is a zoonotic infection caused by the larval stage of Echinococcus granulosus. It primarily affects the liver and lungs, with soft tissue involvement being rare. Coexisting hepatic conditions such as hepatitis B can complicate therapy, as commonly used antihelminthic drugs tend to be hepatotoxic. This report focuses on a 37-year-old woman who presented with a painful swelling in the right thigh after travelling to Bulgaria. Imaging revealed a multiloculated cystic lesion consistent with hydatid disease, confirmed by fine-needle aspiration. She was started on albendazole and praziquantel, but treatment was complicated by an incidental finding of hepatitis B and suspected drug-induced hepatotoxicity. Surgical excision was performed, and she remains under regular multidisciplinary follow-up with MRI surveillance. This case highlights the diagnostic difficulty of extrahepatic hydatid disease and the importance of individualised management when liver comorbidities restrict antiparasitic therapy.