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Muscular Dystrophy

What is Muscular Dystrophy?

The muscular dystrophies (MD) are a group of genetic diseases characterized by progressive weakness and degeneration of the skeletal muscles that control movement. There are many forms of muscular dystrophy, some noticeable at birth (congenital muscular dystrophy), others in adolescence (Becker MD), but the 3 most common types are Duchenne, facioscapulohumeral, and myotonic. These three types differ in terms of pattern of inheritance, age of onset, rate of progression, and distribution of weakness.

Duchenne MD primarily affects boys and is the result of mutations in the gene that regulates dystrophin - a protein involved in maintaining the integrity of muscle fiber. Onset is between 3-5 years and progresses rapidly. Most boys become unable to walk at 12, and by 20 have to use a respirator to breathe.

Facioscapulohumeral MD appears in adolescence and causes progressive weakness in facial muscles and certain muscles in the arms and legs. It progresses slowly and can vary in symptoms from mild to disabling.

Myotonic MD varies in the age of onset and is characterized by myotonia (prolonged muscle spasm) in the fingers and facial muscles; a floppy-footed, high-stepping gait; cataracts; cardiac abnormalities; and endocrine disturbances. Individuals with myotonic MD have long faces and drooping eyelids; men have frontal baldness.

Is there any treatment?

There is no specific treatment for any of the forms of MD. Respiratory therapy, physical therapy to prevent painful muscle contractures, orthopedic appliances used for support, and corrective orthopedic surgery may be needed to improve the quality of life in some cases. Cardiac abnormalities may require a pacemaker. Corticosteroids such as prednisone can slow the rate of muscle deterioration in patients with Duchenne MD but causes side effects. Myotonia is usually treated with medications such as mexiletine, phenytoin, or quinine.

What is the prognosis?

The prognosis of MD varies according to the type of MD and the progression of the disorder. Some cases may be mild and progress very slowly over a normal lifespan, while other cases may have more marked progression of muscle weakness, functional disability, and loss of the ability to walk. In Duchenne MD, death usually occurs in the early 20s.

What research is being done?

The NINDS supports a broad program of research on MD. The goals of these studies are to understand MD and to develop techniques to diagnose, treat, prevent, and ultimately cure muscular dystrophy.