An unusual variant of Becker muscular dystrophy.

We report on 5 brothers with slowly progressive limbgirdle weakness. Calf hypertrophy was absent. The levels of creatine kinase, electromyography, and findings from a muscle biopsy specimen were compatible with muscular dystrophy. The propositus's biopsy specimen also showed numerous rimmed vacuoles. DNA analysis revealed a deletion in the dystrophin gene, establishing a diagnosis of Becker muscular dystrophy. Both the absence of calf hypertrophy and the presence of rimmed vacuoles are unusual features in this disorder.