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Help for Patients and Caregivers : Muscular Dystrophy

Quick reference directory

What is Muscular Dystrophy?
What are the forms of Muscular Dystrophy?
How do the forms of Muscular Dystrophy differ?
What causes Muscular Dystrophy?
Are Muscular Dystrophies always inherited?
Is Muscular Dystrophy contagious?
Is a family medical history important?
How is Muscular Dystrophy diagnosed?
What are some common diagnostic tests?
Is there any treatment?

 


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


What are the forms of muscular dystrophy?

The major forms of muscular dystrophy are myotonic, Duchenne, Becker, limb-girdle, facioscapulohumeral, congenital, oculopharyngeal, distal and Emery-Dreifuss.

Some of these names are based on the locations of affected muscles. For example, "facioscapulohumeral" refers to the muscles that move the face, scapula (shoulder blade) and humerus (upper arm bone). Others are based on the type of muscle problem involved ("myotonic" means difficulty relaxing muscles), the age of onset of the disease (as in "congenital," or birth-onset, dystrophy), or the doctors who first described the disease (Duchenne, Becker, Emery and Dreifuss are doctors' names).

As the root causes (gene defects) of the muscular dystrophies are discovered, doctors are beginning to change their thinking about how to classify some of the dystrophies. 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. In other cases, diseases that looked different have been found to be one disease with variations in severity. This is the case with Duchenne and Becker dystrophies.


How do the forms of muscular dystrophy differ?

They differ in severity, age of onset, muscles first and most often affected, the rate at which symptoms progress, and the way the disorders are inherited.


What causes muscular dystrophy?

Flaws in muscle protein genes cause muscular dystrophies. Each cell in our bodies contains tens of thousands of genes. Each gene is a string of the chemical DNA and is the "code" for a protein. (Another way to think of a gene is that it's the "instructions" or "recipe" for a protein.) If the recipe for a protein is wrong, the protein is made wrong or in the wrong amount or sometimes not at all..


Are muscular dystrophies always inherited?

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.


Is muscular dystrophy contagious?

No. Genetic diseases aren't contagious.


Is a family medical history important?

Yes. Because the muscular dystrophies can be inherited, it's important for the doctor to know if anyone in the family ever had a similar disorder.


How is muscular dystrophy diagnosed?

A doctor makes a diagnosis by evaluating the patient's medical history and by performing a thorough physical examination. Essential to diagnosis are details about when weakness first appeared, its severity, and which muscles are affected. Diagnostic tests may also be used to help the doctor distinguish between different forms of muscular dystrophy, or between muscular dystrophy and other disorders of muscle or nerve.


What are some common diagnostic tests?

Studying a small piece of muscle tissue taken from an individual during a muscle biopsy can sometimes tell a physician whether a disorder is muscular dystrophy and which form of the disease it is.

In Duchenne and Becker muscular dystrophy, a muscle protein called dystrophin is either missing, deficient or abnormally formed. This protein can be examined in the muscle sample.

The reason for the flawed or deficient muscle protein is a flawed gene for dystrophin. A test that involves looking at this gene -- DNA testing -- can be done to diagnose or rule out Duchenne or Becker muscular dystrophies.

Another diagnostic test is the electromyogram (EMG). To do this test, small electrodes are put into the muscle, which allows the doctor to measure the electrical impulses coming from the muscle. The test is uncomfortable.

Another test often performed measures nerve conduction velocity (NCV). During this test, electrical impulses are sent down the nerves of the arms and legs. By measuring the speed of these impulses with electrodes placed on the skin, the doctor can determine whether the nerves are functioning normally. This test is also uncomfortable.

Blood enzyme tests are helpful because degenerating muscles become "leaky." They leak enzymes (proteins that speed chemical reactions), which can then be detected in the blood. The presence of these enzymes in the blood at higher than normal levels may be a sign of muscular dystrophy. One such enzyme is creatine kinase, or CK. The CK level is elevated in many forms of muscular dystrophy, some forms resulting in a higher level than others.


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.


For more information on Muscular Dystrophy visit

National Institute of Neurological Disorders and Stroke
Muscular Dystrophy Association
Muscular Dystrophy Association FAQ