Population data on benign and severe forms of X-linked muscular dystrophy.

Epidemiological data on Becker muscular dystrophy (BMD) and Duchenne muscular dystrophy (DMD) from a large sample of the Italian population are reported. For BMD the incidence rate was found to be 5.5 X 10(-5) live-born males (lbm) and the prevalence rate, 13.1 X 10(-6); the mutation rate was estimated to be about 6.0 X 10(-6). For DMD the incidence and prevalence rates were found to be respectively 26 X 10(-5) lbm and 31.6 X 10(-6). The DMD mutation rate obtained by the Haldane formula was 86.6 X 10(-6) and by the semi-direct method, 65.6 X 10(-6). The results are discussed in the light of possible allelism of BMD and DMD.