In male patients, a nonsense or frameshift mutation in the DMD gene cause a severe phenotype, Duchenne muscular dystrophy (DMD; OMIM 310,200), while in-frame deletion/duplication or missense mutation result in a milder phenotype, Becker muscular dystrophy (BMD; OMIM 300,376) (Monaco et al. 1988). Here, DMD is linked to Becker muscular dystrophy.