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Duchenne Muscular Dystrophy (DMD)

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Duchenne Muscular Dystrophy (DMD), also known as Pseudohypertrophic, is the most common form of muscular dystrophy (MD) that occurs when the X-chromosome fails to make dystrophin, a protein that surrounds the muscle fibers and help muscle cells work properly. It is characterized by decreasing muscle mass and progressive loss of muscle function in male children. It is extremely rare in females.[1]


Contents

History

DMD was first described by French neurologist, Guillaume Duchenne, in the 1860s. Little was known about the cause of an of the Muscular Dystrophies until the 1980's. In 1986, scientists lead by Dr. Louis M. Kunkle announced that they had identified the gene that caused DMD. In late 1987, the scientists found that a deficiency in a protein called dystrophin lead to the deterioration of muscles.


Symptoms

Symptoms begin between the ages of 2 and 6 in males. It begins with a gradual weakening of the skeletal or voluntary muscles including those in the hips, pelvic area, thighs and shoulders. Calves are often enlarged (pseudohypertrophy).[2]

Females are not usually affected by the gene because they receive two X-chromosomes from their parents unlike males who only receive one. The second X-chromosome can make up the dystrophin necessary to maintain relatively normal muscle function. Girls are carriers of the gene but often show minimal or no signs of its effects. However, some do develop cardiomyopathy. Girls who show effects of the gene often seem weak or fatigued especially during light exercise.[3]


Progression

Eventually, all voluntary muscles are affected. By the early teens and twenties, the heart and respiratory muscles begin to weaken making it difficult to breath and circulate blood. Survival is rare beyond the early 30's. DMD is 100% fatal.[4]


Inheritance

DMD is a genetic disorder. It is carried through the X-chromosome from mother to child. Females and males have a 50% chance of carrying the gene if they inherit it from a parent. Since girls are carriers of the gene, they have a high risk of transferring it to their children as well as developing cardiomyopathy.[5]


Treatment

Contractures

Contractures are fixation of joints caused by the degeneration of the surrounding muscles. Range-of-motion exercises can help delay contractures by keeping tendons from shortening prematurely. A physical therapist can show you how to perform the exercises correctly. Braces on the arms or legs can also help. Surgery may be required. A heel chord surgery may be performed to treat contractures that affect walking. After surgery, foot braces may be necessary.[6]


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