Focal myositis of unilateral leg

Focal myositis is a rare, benign inflammatory pseudotumor of the skeletal muscle of unknown etiology. In Korea, there is no case report of focal myositis, which is not combined with connective tissue disease. We present an unusual case of focal myositis with ankle contracture, involving more than two muscles. A 26-year-old man visited our clinic complaining of right ankle contracture and leg muscle pain. Physical examination revealed no muscle weakness or any other neurological abnormality. T2-weighted magnetic resonance imaging of the right leg demonstrated diffuse high signal intensity of the right gastrocnemius, flexor digitorum longus, and tibialis anterior muscles. Needle electromyography showed profuse denervation potentials with motor unit action potentials of short duration and small amplitude from the involved muscles. All these findings suggested a diagnosis of focal inflammatory myositis and the patient was put under oral prednisolone and physical therapy.