Duchenne's muscular dystrophy is an inherited disorder. Symptoms appear before age 6 and may appear as early as infancy. Muscle weakness also occurs in the arms, neck, and other areas, but not as severely as in the lower half of the body. Muscle contractures occur in the legs and heels, causing inability to use the muscles because of shortening of muscle fibers and fibrosis of connective tissue. By age 10, braces may be required for walking, and by age 12, most patients are confined to a wheelchair.
Bones develop abnormally, causing skeletal deformities of the chest and other areas.
Muscular weakness and skeletal deformities contribute to frequent breathing disorders. Cardiomyopathy occurs in almost all cases. Intellectual impairment is common but is not inevitable and does not worsen as the disorder progresses. Duchenne's muscular dystrophy occurs in approximately 2 out of 10,000 people. Symptoms usually appear in males 1 to 6 years old.