Inherited disease that causes progressive weakness in the skeletal (and occasionally heart) muscle. Muscle tissue degenerates and regenerates randomly and is replaced by scar tissue and fat. There is no specific treatment. Physical therapy, braces, and corrective surgery may help. Duchenne muscular dystrophy, the most common, strikes only males. Symptoms, including frequent falls and difficulty in standing up, start in boys 3–7 years old; muscle wasting progresses from the legs to the arms and then the diaphragm. Pulmonary infection or respiratory failure usually causes death before age 20. The gene can now be detected in female carriers and male fetuses. Becker dystrophy, also sex-linked, is less severe and begins later. Patients remain able to walk and usually survive into their 30s and 40s. Myotonic muscular dystrophy affects adults of both sexes, with myotonia and degeneration two to three years later, along with cataracts, baldness, and gonadal atrophy. Limb-girdle dystrophy affects the pelvic or shoulder muscles in both sexes. Facioscapulohumeral (face, shoulder-blade, and upper-arm) dystrophy starts in childhood or adolescence and affects both sexes; after initial symptoms of difficulty raising the arms, the legs and pelvic muscles can be affected; the main facial effect is difficulty in closing the eyes. Life expectancy is normal.
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