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We examined dystrophin,the protein product of the Duchenne muscular dystrophy gene,in muscle biopsy specimens from 4 male patients with quadriceps myopathy,all of whom showed a mild and slowly progressive myopathy confined to the quadriceps muscles.All 4 patients had clear abnormalities of dystrophin,and were diagnosed as having Becker muscular dystrophy by both immunofluorescence and immunoblot examinations;that is, dystrophin of an abnormal molecular mass was visualized in muscle cryosections as"patchy"or discontinuous immunostaining at the surface membrane of the muscle fibers.One patient had a brother who showed widespread myopathic changes consistent with typical Becker muscular dystrophy.We conclude that the syndrome called quadriceps myopathy includes a group of forme fruste Becker muscular dystrophy. |
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