Muscular Dystrophies are a group of more than 30 genetic diseases that are clinically manifested in patients as progressive muscle weakness with associated loss of mobility, agility, and body movements as a result of defects in genes for the production of muscle proteins that result in the death of muscle cells and tissue. Some forms of MD are seen in infancy or childhood, while others may not appear until middle age or later. Duchenne Muscular Dystrophy (DMD) is the most common form of MD and primarily affects boys. It is caused by the absence of dystrophin, a protein involved in maintaining the integrity of muscle.
Mercuri, E. and F. Muntoni (2013). "Muscular dystrophies." The Lancet 381(9869): 845-86.