Becker-type muscular dystrophy.

This is a review of clinical, cardiologic, electrophysiologic, pathologic, and serum creatine kinase changes in eight families with slowly progressive X-linked Becker-type muscular dystrophy. All but one of the patients were able to walk until the age of 16 years, and most lived beyond 20. In every family, electromyography and muscle biopsy showed features which, on the basis of classical criteria, were interpreted as those of both myopathy and denervation, although among patients and among families, one or the other of these processes predominated. The most frequent biopsy picture was of fiber atrophy and hypertrophy, with many split and angulated fibers, and clumps of pyknotic nuclei. Necrosis, phagocytosis, regeneration, endomysial fibrosis, and some fatty infiltration were commonly seen. Review of a family originally described by Becker showed a similar biopsy picture; These pathologic changes are separable from those of Duchenne muscular dystrophy, but they often overlap with those seen in other chronic neuromuscular diseases.