Muscular dystrophy (MD) is a group of diseases that cause weakness in the muscles closest to the torso (mid-section of the body). There are several kinds of muscular dystrophy. The most common childhood MD is Duchenne's muscular dystrophy (DMD).
DMD generally appears from age three to six years and worsens rapidly. At first, muscle weakness and wasting (atrophy) occurs in the pelvic (hipbone) area, followed by similar problems in the shoulder muscles. Eventually, muscle weakness and atrophy affect the trunk and forearms and gradually spread to the major muscles of the body.
Depending on the type of disease, symptoms of muscular dystrophy may include a waddling way of walking, difficulty climbing stairs or rising from sitting and repeated falling. As the disease worsens, other abnormalities may develop, such as curvature of the spine, wasting of thigh muscles, abnormal enlargement of the calves and enlargement of the heart.
Duchenne muscular dystrophy is caused by a defective gene for dystrophin (a protein that helps keep muscle cells intact).
Physicians suspect MD when a young boy becomes weak and grows weaker. An enzyme (creatinine kinase) leaks out of muscle cells, causing enzyme levels in the blood to be abnormally high. However, high blood levels of creatinine kinase don't necessarily mean that a child has muscular dystrophy. Other muscle diseases may also cause high levels of this enzyme.
A muscle biopsy is usually taken in order to confirm MD. A positive MD biopsy will contain dead tissue and abnormally large muscle fibers. In the late stage MD, fat and other tissues replace the dead muscle tissue.
DMD is diagnosed when special tests show extremely low levels of the protein dystrophin in the muscle. Other tests given may include electrical studies of muscle function (electromyography) and nerve conduction studies.
There is currently no known cure for any of the muscular dystrophies. However, physical therapy and exercise may help prevent muscles from contracting permanently around joints. Sometimes surgery is needed to release tight, painful muscles.
Prednisone, a powerful steroid drug, is often given to DMD patients as a way to temporarily relieve muscle weakness. Gene therapy is being investigated as a way to help muscles produce dystrophin.
The GenRISK Adult Genetics Program at Cedars-Sinai offers genetic risk assessment, testing and counseling for persons who suspect they may have an inherited risk for specific diseases or conditions.
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