Duchenne's muscular dystrophy

Alternative names:

muscular dystrophy - Duchenne's; pseudohypertrophic muscular dystrophy

Definition:

An inherited disorder characterized by rapidly progressive muscle weakness of the legs and pelvis; later affecting the whole body.

Causes, incidence, and risk factors:

Duchenne's muscular dystrophy is a rapidly progressive form of muscular dystrophy. A slowly progressive muscular dystrophy that is very similar to Duchenne's also exists (Becker's muscular dystrophy). Duchenne's muscular dystrophy is an inherited disorder.

Symptoms appear before age 6 and may appear as early as infancy. There is progressive muscle weakness of the legs and pelvis, which is associated with a loss of muscle mass (wasting). Muscle weakness also occurs in the arms, neck, and other areas, but not as severely as in the lower half of the body. Calf muscles initially enlarge; the enlarged muscle tissue is eventually replaced by fat and connective tissue (pseudohypertrophy). 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. The cause of this impairment is related to an abnormal gene for dystrophin protein (a specific type of protein in the body).

Duchenne's muscular dystrophy occurs in approximately 2 out of 10,000 people. Symptoms usually appear in males 1 to 6 years old. Females are carriers of the gene for this disorder but rarely develop symptoms. Because this is an inherited disorder, risks include a family history of Duchenne's muscular dystrophy.