Muscular dystrophy (MD) is a group of inherited diseases in which the muscles that control movement (called voluntary muscles) progressively weaken. In some forms of this disease, the heart and other organs are also affected.
Muscular dystrophy can appear in infancy up to middle age or later, and its form and severity are determined in part by the age at which it occurs. Some types of muscular dystrophy affect only males; some people with MD enjoy a normal life span with mild symptoms that progress very slowly; others experience swift and severe muscleweakness and wasting, dying in their late teens to early 20s.