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Anatomy => Muscle => Muscular Dystrophy
Muscular Dystrophy
INTRODUCTION
Muscular Dystrophy, crippling disease characterized by gradual wasting of skeletal muscle. The clinical course is progressive, with increased weakness and diminution in muscle mass and function until the patient is confined to a wheelchair; remissions do not occur. Four clinical forms of the disease are recognized, based on pattern of inheritance, age when symptoms are first noted, and distribution of the muscles earliest involved. Microscopic abnormalities of skeletal muscle are found in each type.
FORMS AND SYMPTOMS
In the Duchenne form of the disease, symptoms usually are noted before age five. The muscles first affected are those of the pelvis and trunk, resulting in spinal deformity and a waddling gait. Wasting of almost all muscle groups may be advanced by the late teens. Death may result from respiratory weakness or from involvement of the heart muscle. Because inheritance of this form is by an X-linked recessive mechanism, virtually all patients are boys. Becker muscular dystrophy is a milder form of Duchenne muscular dystrophy.
The facio-scapulo-humeral form of the disease affects both sexes equally and results in weakness and wasting of the shoulder girdle and upper arms. It is usually noted around the onset of puberty. The characteristic weakness of the facial muscles may occasionally be seen during the first years of life. Most patients remain ambulatory until an advanced age.
The limb-girdle type of the disease affects both sexes. Muscles of either the shoulder or hip girdle, or both, may be involved. The disease may begin early or late in life, and usually the course is slow. In the late stages most of the muscles of the body may be affected.
In myotonic muscular dystrophy, delayed relaxation of the muscles accompanies wasting and weakness. Cataracts of both eyes may occur, and reproductive functions may be disturbed. The age of onset and severity of symptoms are variable, but the disease tends to occur earlier and is more severe in later generations of an affected family. Myotonic muscular dystrophy affects both sexes, but children of affected mothers are more likely to inherit a severe form of the disease than children of affected fathers.
TREATMENT
Muscular dystrophy has its origin in a genetic mutation, but the biochemical steps by which this genetic defect manifests itself in the degenerative process in the muscle are not known. Because specific treatment is not available, general measures, including physical and occupational therapy, are used. Genetic tests for mutations in the different genes causing muscular dystrophy provide rapid and accurate diagnosis for patients. In the case of the X-linked Duchenne and Becker muscular dystrophies, these tests allow detection of female carriers of the disorders.
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