Chronic Leg Swelling: Uncovering a Rare Hydatid Cyst

Hydatidosis is an infection caused by the helminth <i>Echinococcus granulosus</i>. The liver and lungs are the most frequently affected organs, primarily due to their roles in filtering blood. Primary hydatidosis of the skeletal muscles is an exceedingly rare condition, often asymptomatic, which can lead to its misdiagnosis as a more common soft tissue tumour. This case report presents a case of primary hydatidosis localized in the vastus medialis muscle of the thigh in a man in his early 70s. The patient exhibited a chronic swelling in his right thigh that persisted for four years, gradually increasing in size and associated with pain. Diagnostic challenges arose due to the atypical site of the cyst, but ultrasound and MRI ultimately confirmed the presence of a hydatid cyst. Thus, it highlights the importance of maintaining a high index of suspicion for hydatidosis, particularly in regions with high endemicity, like India, where early recognition and accurate diagnosis are vital for effective management.