A primary hydatid cyst of the gracilis: a case report.

Primary hydatid disease of the skeletal muscle without systemic involvement is rare. A 40-year-old woman presented with a painful mass in her medial left upper thigh. She was misdiagnosed as having a deep intramuscular abscess and a fine needle aspiration was performed, but the fluid came out crystal clear. Further inquiry revealed that her 16-year-old daughter had been operated on twice for liver and lung hydatid disease. Thus, a provisional diagnosis of hydatid disease was made. An echinococcal haemagglutination test was positive. Ultrasonography and magnetic resonance imaging findings were consistent with a type-2 hydatid cyst showing a 'water-lily' sign. The cystic mass within the left gracilis was resected en bloc. Adjunctive albendazole chemotherapy (400 mg/day) was prescribed for 3 months. At the 22-month follow-up, the patient remained free of symptoms.