Focal inflammatory myopathy.

We report three patients with inflammatory myopathy who presented clinically with weakness and wasting of only one limb. The myopathy progressed over 6 months and 5 years, respectively, in two patients and was stable after 8 years in the third patient. One patient had a skin rash. Serum CK was elevated in the two patients with progressive disease. Electromyography showed brief duration, small amplitude motor unit potentials and fibrillations in the affected limbs. Muscle biopsy revealed variable fiber size, degenerating and regenerating fibers, and inflammatory foci. Vasculitis was seen in the patient with skin lesions and marked fibroblastic proliferation in the patient with the most chronic course. Immunosuppressive therapy has arrested the progression in the two patients treated; both have regained strength.