Muscular Dystrophy
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The muscular dystrophies (MD) are a group of genetic diseases characterized
by progressive weakness and degeneration of the skeletal muscles which control
movement. There are many forms of muscular dystrophy, some noticeable at birth
(congenital muscular dystrophy), others in adolescence (Becker MD), but the
3 most common types are Duchenne, facioscapulohumeral, and myotonic. These
three types differ in terms of pattern of inheritance, age of onset, rate of
progression, and distribution of weakness. Duchenne MD primarily affects boys
and is the result of mutations in the gene that regulates dystrophin - a protein
involved in maintaining the integrity of muscle fiber. Onset is between 3-5
years and progresses rapidly. Most boys become unable to walk at 12, and by
20 have to use a respirator to breathe. Facioscapulohumeral MD appears in adolescence
and causes progressive weakness in facial muscles and certain muscles in the
arms and legs. It progresses slowly and can vary in symptoms from mild to disabling.
Myotonic MD varies in the age of onset and is characterized by myotonia (prolonged
muscle spasm) in the fingers and facial muscles; a floppy-footed, high-stepping
gait; cataracts; cardiac abnormalities; and endocrine disturbances. Individuals
with myotonic MD have long faces and drooping eyelids; men have frontal baldness.
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There is no specific treatment for any of the forms of MD. Respiratory therapy,
physical therapy to prevent painful muscle contractures, orthopedic appliances
used for support, and corrective orthopedic surgery may be needed to improve
the quality of life in some cases. Cardiac abnormalities may require a pacemaker.
Corticosteroids such as prednisone can slow the rate of muscle deterioration
in patients with Duchenne MD but causes side effects. Myotonia is usually treated
with medications such as mexiletine, phenytoin, or quinine.
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The prognosis of MD varies according to the type of MD and the progression
of the disorder. Some cases may be mild and progress very slowly over a normal
lifespan, while other cases may have more marked progression of muscle weakness,
functional disability, and loss of the ability to walk. In Duchenne MD, death
usually occurs in the early 20s.
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Facioscapulohumeral Dystrophy
(FSHD)
Muscular Dystrophy Association
Muscular Dystrophy Family Foundation
Parent Project Muscular
Dystrophy (PPMD)
International
Myotonic Dystrophy Organization
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