Muscles in many diseases appeared to be wasting away, and the doctors theorized that they somehow weren't being properly nourished. Today, we know that many muscle-wasting diseases are caused by defects in genes for muscle proteins. Most of these proteins appear to play a role in supporting the structure of muscle fibers, although some may play a role in the biochemical processes that go on in muscle fibers. The term muscular dystrophy refers to a group of genetic diseases marked by progressive weakness and degeneration of the skeletal, or voluntary, muscles, which control movement. The muscles of the heart and some other involuntary muscles are also affected in some forms of muscular dystrophy, and a few forms involve other organs as well.
Muscular dystrophy can affect people of all ages.
While some forms first become apparent in infancy or childhood, others may not appear until middle age or later. With improved medical care, particularly of problems affecting the heart and lungs, children with muscular dystrophy are living further into adulthood than ever before. Some of these names are based on the locations of affected muscles. In some cases, a type of muscular dystrophy that looked like it might be one disease has been found to be several different diseases, caused by several different gene defects. This is true for limb-girdle, congenital and distal dystrophies.