Muscular dystrophy (MD) is a general term used to describe a number of inherited disorders characterized by progressive weakness and wasting of the muscles. The most common and severe type is Duchenne’s MD, in which a genetic defect leads to severe depletion of the muscle protein called dystrophin.
Becker’s MD is similar to Duchenne’s MD, but milder, resulting from a defect in the same gene. Others include facioscapulohumeral MD, myotonic MD, and various types of limb-girdle MDs.
The types of MD are classified according to the location of muscles involved, the age when symptoms appear, the rate that symptoms progress, and the manner in which the defective gene is passed on. (For example, the genes for Duchenne’s and Becker’s MD are X-linked recessives; that is, they generally affect males only but are carried and passed on by women.)
Symptoms and prognosis vary, depending on the type of MD. The disease may affect some or all muscles, may develop during childhood or adulthood, may progress very gradually or rapidly, and may or may not become severely disabling.
Boys with Duchenne’s MD are usually dependent on a wheelchair by the age of 12 and may not live past age 20; on the other hand, people with facioscapulohumeral MD often have a normal life span and, because the leg muscles are only mildly affected, usually remain able to walk. Some forms of MD affect the heart and thus result in cardiomyopathy.
What Causes Muscular Dystrophy?
- All forms of MD result from some type of genetic defect. In most cases, the defect is inherited and affects various relatives throughout a family. In some cases, a new genetic mutation is responsible.
Symptoms of Muscular Dystrophy
- Progressive muscle weakness, wasting, and loss of function (The muscle groups affected depend on the type of MD.)
- In Duchenne’s MD, delayed development of basic muscle skills and coordination in children. Signs include poor balance with frequent falls, walking difficulty with waddling gait, and limited range of movement. Muscular and skeletal deformities, including curvature of the spine with protruding abdomen, are likely. Respiratory failure and heart rhythm problems may occur.
- Joint contractures and calf enlargement (in Duchenne’s and Becker’s MD)
- Cataracts, frontal baldness, drooping eyelids, gonadal atrophy, and mild mental impairment (with myotonic dystrophy)
- Intellectual impairment (most common in Duchenne’s MD)
Prevention of Muscular Dystrophy
- If you have a family history of MD, you may choose to see a genetic counselor before planning to have a child. Genetic tests can determine whether you carry an MD gene or an unborn child has MD.
Diagnosis of Muscular Dystrophy
- Patient history and physical examination are needed.
- A muscle biopsy (removal of a small tissue sample for microscopic examination) may be performed to check that the weakness is due to muscle disease.
- Electrical activity in the muscles may be measured and analyzed (electromyography).
- DNA tests (genetic testing) can prove the exact diagnosis.
How to Treat Muscular Dystrophy
- There is no specific treatment to cure or halt the progression of MD.
- In Duchenne’s MD, corticosteroids such as prednisone can slow the early course of weakness only.
- Physical therapy, exercise, orthopedic devices (such as braces or wheelchairs) or corrective orthopedic surgery may help to preserve muscle function, reduce joint contractures and improve quality of life.
When to Call a Doctor
- If you or your child appears to be exhibiting the symptoms of muscular dystrophy, call a doctor.
- Consult a doctor if there is a history of muscular dystrophy in your or your spouse’s family and you are considering having a child.
Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference
Simeon Margolis, M.D., Ph.D., Medical Editor
Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50
Updated by Remedy Health Media