The term "Muscular Dystrophy" includes any of several inherited diseases characterized by progressive wasting of the skeletal muscles. There are five main forms of the disease. They are classified according to the age at onset of symptoms, the pattern of inheritance, and the part of the body primarily affected.

Duchenne muscular dystrophy, the most common form, begins with leg weakness before age 3 and progresses rapidly, with death often occurring before age 30, often because of involvement of lung or heart muscle. Research has shown that the abnormal gene fails to produce an essential skeletal muscle protein called dystrophin.

Becker's muscular dystrophy is similar to the Duchenne form, but appears somewhat later in life and progresses more slowly.

Fascioscapulohumeral muscular dystrophy primarily involves facial and shoulder muscles. Symptoms can begin from adolescence to around age 40. It is caused by an autosomal dominant trait (at least one parent will have the disease). Progression is usually slow and severe disability is unusual.

Myotonic muscular dystrophy is characterized by an inability of the muscles to relax properly after contraction and primarily affects the muscles of the hands and feet. It usually begins in adulthood and is often accompanied by cataracts, baldness, and abnormal endocrine function.

The limb-girdle form of the disease first affects the muscles of the hip and shoulder areas. Symptoms usually become apparent in late adolescence or early adulthood. This form usually progresses slowly.

There is no known treatment or cure for muscular dystrophy. Supportive measures and exercises can improve the quality of life and preserve mobility for as long as possible. Scientists have begun to identify the genetic abnormalities responsible for multiple dystrophy and hope that further understanding will lead to treatment. Genetic screening is recommended for all family members who might be carriers. Prenatal tests such as chorionic villus sampling and amniocentesis can detect some forms of muscular dystrophy early in a pregnancy.

---from Encyclopedia.com