Duchenne and Becker muscular dystrophies (DMD and BMD) represent the most frequent neuromuscular diseases in human, occurring in one of 3,500 to one in 6,000 live male births depending on the population studied (Bushby et al. (2010)). DMD and BMD are allelic disorders resulting from mutations in the dystrophin gene. In DMD, functioning dystrophin is completely absent from muscle, while in BMD there is some dystrophin present, although not in sufficient amounts for normal muscle function. In addition to skeletal muscle weakness, dystrophin deficiency in the myocardium results in a progressive cardiomyopathy.
Currently there are no approved therapies specific to the treatment of DMD/BMD. High dose corticosteroids are often used to treat muscle weakness and to maintain ambulation as long as possible, but these are associated with unacceptable side effects and/or suboptimal responses. It is also uncertain whether these therapeutics help or hinder cardiac function. Additional therapeutic approaches are needed to treat both the skeletal and cardiac abnormalities of muscular dystrophies.