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Youth Program Central* Search for Schools For Youth With Muscular Dystrophy
MUSCULAR DYSTROPHY WHAT IS MUSCULAR DYSTROPHY? Muscular dystrophy is an inherited disorder characterized by skeletal muscle fiber degeneration which leads to gradually declining muscle strength and bulk. There are a variety of types of muscular dystrophy. (1) This article will focus on Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy (BMD). DUCHENNE MUSCULAR DYSTROPHY Duchenne Muscular Dystrophy was first documented in the 1860's by Guillaume Benjamin Amand Duchenne, a French neurologist. (2) Duchenne Muscular Dystrophy is an X-linked disorder, thus it usually only affects boys. (1) A milder form can occur in some female carriers, although rarely. (4) The disease occurs when a particular gene on the X chromosome is mutated. This particular gene instructs the body how to make dystrophin, a protein. (2) Dystrophin provides muscle fibers with strength, flexibility, and protection from mechanical injury during muscle contraction. Without the protection of dystrophin, the stresses that muscle contraction causes, leads to cracks in the cell membranes of muscle fibers. This activates enzymes that destroy the damaged cells. Unfortunately, the rate at which muscle cell regeneration occurs cannot keep up with the rate at which muscle degeneration occurs; thus, the weakened muscles eventually die. Muscle fibers that are dead are replaced by connective and fatty tissues, which give the affected muscles an enlarged appearance. (3) Duchenne Muscular Dystrophy occurs in around one in 3,500 male births and is the most severe form of muscular dystrophy. Life expectancy for one with Duchenne Muscular Dystrophy is early to mid-twenties. (4) Toddlers with Duchenne Muscular Dystrophy are usually first noted to fall frequently, have difficulty climbing stairs, and calf muscles may look enlarged. (3) As the child enters school, it may be noted that he has a waddling gait and has difficulty maintaining his balance. Between the ages of seven to twelve, most children with Duchenne Muscular Dystrophy will lose the ability to walk. (2) The most dangerous muscle weakness that occurs with Duchenne Muscular Dystrophy is that of the diaphragm. Movement of the diaphragm allows breathing and coughing to occur. Unfortunately, due to ineffective breathing, respiratory infections are the typical cause of death. (4) BECKER MUSCULAR DYSTROPHY Becker Muscular Dystrophy was first documented in the 1950's by Peter Emil Becker, a German doctor. The disease also occurs when a particular gene on the X chromosome is mutated, although the mutations are different from those seen in Duchenne Muscular Dystrophy. Those with Becker Muscular Dystrophy have some dystrophin, but it is lacking in either quantity or quality. Because there is some dystrophin present, the muscles of someone with Becker Muscular Dystrophy do not degenerate as rapidly or severely as one with Duchenne Muscular Dystrophy. (2) Becker Muscular Dystrophy occurs in around 1 in 30,000 male births and is usually not manifested until adolescence or adulthood. Life expectancy for one with Becker Muscular Dystrophy is related to age on onset and severity of symptoms. If symptoms are treated aggressively, a normal life span may be possible. (4) Muscle weakness and a waddling gait are seen with Becker Muscular Dystrophy. Some men with Becker Muscular Dystrophy will lose their ability to walk, but not necessarily in every case. HOW IS MUSCULAR DYSTROPHY DIAGNOSED? A doctor will usually start with a history and physical of the patient. This may be followed by a blood test called a CK level. Creatine kinase (CK) is an enzyme that leaks from damaged muscles and elevated levels indicate that muscle is being destroyed. An electromyography or nerve conduction study may be performed. These particular tests indicate whether the problem is a muscle or nerve issue. Muscle biopsy is used to diagnose whether or not muscular dystrophy is present, and if so, what type. (2) HOW IS MUSCULAR DYSTROPHY TREATED? The goals of treatment include the prevention of complications associated with weakness and decreased mobility. (4) Complications include contractures (fixed joints), spinal curvature, cardiomyopathy (heart muscle weakness), and an ineffective respiratory system because of a weakened diaphragm. A number of research studies are being conducted in the hopes of finding a way to stop or reverse the destruction of muscle that occurs in muscular dystrophy. These projects include gene therapy, stem cell research, pharmaceutical, and dietary studies. REFERENCES 1. Huether, Sue E. and Kathryn L. McCance. Understanding Pathophysiology. St. Louis: Mosby, 1996. 2. Muscular Dystrophy Association. "Facts About Duchenne and Becker Muscular Dystrophies - MDA Publications." http://www.mdausa.org/publications/fa-dmdbmd.html (31 Dec 2003). 3. Metules, Terri. "Duchenne muscular dystrophy. (A New Age for Childhood Diseases)." RN 1 Oct 2002. http://www.rnweb.com/be_core/ADS?filename=be_core/content/journals/r/data/2002 /1001/mdadults.html&title=A+new+age+for+childhood+diseases%3A+Duchenne+ muscular+dystrophy&navtype=r&site=r&query=muscular+dystrophy (31 Dec 2003). 4. Robinson, Richard. Muscular Dystrophy. Gale Encyclopedia of Medicine. 1 Jan 1995. http://www.findarticles.com/cf_0/g2601/0009/2601000924/p1/article.jhtml. (31 Dec 2003).
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