Despite numerous reports about dystrophin alterations in Duchenne and Becker muscular dystrophies and dilated cardiomyopathy, the function of dystrophin gene promoters has not yet been completely elucidated. We report the first case of a DNA segment deletion encompassing promoters M and P of the human dystrophin gene, which caused a very severe muscle phenotype without cardiomyopathy, in a 13-year-old boy. These data indicate that the simultaneous lack of promoters P and M results in dramatic consequences in skeletal muscle but not in the heart.