Early-onset benign autosomal-dominant limb-girdle myopathy with contractures (Bethlem myopathy).

We report the first Japanese patients, a mother and son, with early-onset, benign, autosomal-dominant, limb-girdle myopathy with contractures (Bethlem myopathy). The clinical features revealed predominantly proximal muscle weakness--especially in the limb-girdle muscles--joint contractures increasing with age, a benign course, and the absence of cardiac involvement. Muscle histology revealed nonspecific myopathy changes without dystrophic features. Electromyogram revealed a reduced interference pattern with a giant spike suggesting a neurogenic process.