[A case of pseudophlebitis of the great saphenous vein: focal nodular myositis of the gracilis muscle].

A case of focal myositis in a healthy 68-year-old woman is described. The patient was admitted for evaluation of a painful soft-tissue mass localised on the medial side of the left thigh, initially misdiagnosed as thrombophlebitis of the v. saphena magna. Laboratory data were normal, in particular sedimentation rate and muscle enzyme levels. After exclusion of venous thrombosis, the mass localised in the left m. gracilis was surgically removed. Histologic examination of the biopsy specimen showed muscle cell necrosis and severe inflammation, with lymphocytic infiltration leading to the diagnosis of focal myositis. This is a rare benign inflammatory pseudotumour of skeletal muscle. The aetiology and pathogenesis of the disease remain unclear. It is most commonly seen in the lower extremities and may mimic thrombophlebitis or soft-tissue neoplasm. Ultrasound and magnetic-resonance scans are helpful, but definitive diagnosis is obtained only by histology. Because recurrent lesions in other skeletal muscles are possible, and a third of patients develop polymyositis, a follow-up of several years is recommended.