|
Muscular dystrophy is an inherited group of muscle disorders, which cause a slow but progressive degeneration of the muscles. There are various different types of muscular dystrophy including Becker's muscular dystrophy, Duchenne muscular dystrophy, myotonic dystrophy, limb-girdle muscular dystrophy, Landouzy-Dejerine muscular dystrophy and facioscapulohumeral muscular dystrophy, which are also known as Steinert's disease. Two other muscle diseases that are sometimes related to muscular dystrophy are myotonia congenita or Thomsen's disease and Pompe's disease. Although all forms of muscular dystrophy are considered rare, the most common form is Duchenne’s, which occurs in two out of ever 10,000 young men. But the defective gene that causes Duchenne's muscular dystrophy is not the same one that causes Becker's muscular dystrophy.
Although the actual cause of this disorder is unknown, it is known that a gene defect is responsible for the onset. Even though females are known to carry the defective gene they remain unaffected. The recessive gene that is responsible is carried on the X chromosome and while females who are carriers have a normal X chromosome that compensates for the defective gene, males do not. With Duchenne's muscular dystrophy the young men are almost totally missing an essential muscle protein known as dystrophin. This protein is believed to be important to maintain the structure of the muscle cells. On the other hand young men with Becker's muscular dystrophy do produce this essential muscle protein but it does not function properly because it is over sized.
Duchenne's muscular dystrophy will produce symptoms between the ages of 3 and 7 in young boys. It begins with a weakness in the pelvic area first and then progresses to the shoulder muscles. As the disorder escalates the muscles weaken and enlarge although the muscle tissue is weak. The heart muscle will also enlarge creating problems with the heartbeat that can be detected on an electrocardiogram. In most cases the young man affected will have a waddling walk, will often fall, will have difficulty rising from a sitting position, has a difficult time climbing stairs, will be unable to fully extend the arms and legs, and may develop scoliosis or an abnormally curved spine. In most cases young men with Duchenne's muscular dystrophy are confined to a wheel chair between the ages of 10 and 12. Becker's muscular dystrophy produces symptoms that are less severe and usually appear around age 10.
Myotonic dystrophy affects the muscles in the hands and feet. Limb-girdle muscular dystrophy begins late in childhood affecting mainly the muscles of the shoulders and hips. Facioscapulohumeral muscular dystrophy affects only the muscles of the upper arms, face and shoulder girdle. Landouzy-Dejerine muscular dystrophy, which is transmitted by an autosomal dominant gene, affects the face, shoulder and lower leg muscles. Steinert's disease affects both males and females causing the muscles to be unable to relax after contracting while Thomsen's disease causes a stiffness of the legs, hands and eyelids. Pompe's disease, which is a glycogen storage disease, affects the liver, heart, nerves and muscles. Although there is no known cure for muscular dystrophy, exercise and physical therapy are recommended. Corticosteriod drugs and gene therapies are being studied to help relieve the symptoms.
|
| |
