Adult acid maltase deficiency.

A 30-year-old man was referred for neurologic evaluation because of elevated creatine kinase. He had noted symptoms of proximal arm and distal leg weakness for several years, and, on examination, he had weakness in a scapuloperoneal distribution. An electromyogram showed myotonic discharges in the paraspinous muscles, and a muscle biopsy revealed severe vacuolar myopathy. Biochemical analysis of muscle showed acid maltase deficiency. The patient's only brother had childhood-onset acid maltase deficiency and died of respiratory failure at age 27. Acid maltase deficiency may have heterogeneous presentations within a family, and adult AMD can present as a scapuloperoneal neuromuscular syndrome.