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 occur at different ages of a person's life, ranging from infancy to middle age or later. The type of the disease is based in part on when in a person's life muscular dystrophy appears. It also depends on the severity of the muscle weakness, which muscles are affected, the rate of symptom progression, and the way the disease arises. Some types of muscular dystrophy affect only males; others affect both males and females. Some sufferers still enjoy a normal life span with mild symptoms that progress very slowly, while others experience fast and severe muscle weakness and wasting, dying in their late teens to early 20s.  WebMD