Muscular dystrophies (MDs) are a group of disorders that share three characteristics: They are inherited, they cause progressive weakness and muscle wasting, and the primary defect is localized to skeletal muscle, sparing the nerves. Although selected limb muscles develop some degree of weakness in all dystrophies, to distinguish among the different types, it is critical to know the mode of inheritance, the age of onset, and whether muscles other than limb muscles are also affected. For example, some dystrophies additionally affect eye and lip closure; another type affects eye movement ability, as well as swallowing and speech.

More than thirty types of MDs are now recognized. Three of the more prevalent forms—Duchenne, myotonic, and limb-girdle dystrophies—will be discussed from the standpoint of the presenting symptoms, age of onset, inheritance pattern, causative genes, and the availability of prenatal and presymptomatic molecular testing.

Duchenne Muscular Dystrophy