Asymptomatic Becker muscular dystrophy: expression of dystrophin and dystrophin-related protein.

The expression of dystrophin and a dystrophin-related protein in muscle from 3 asymptomatic Becker muscular dystrophy patients is reported. Histology demonstrated moderate variation in fiber size with clustered basophilic regenerating fibers. Immunostaining for dystrophin revealed a patchy appearance on most fibers, but never on clustered regenerating fibers. Those regenerating fibers did, however, have positive immunoreactivity to a dystrophin-related protein. It is speculated that overexpression of the dystrophin-related protein in regenerating muscle fibers may contribute to the slow progression of muscle weakness or atrophy.