muscular dystrophy

muscular dystrophy One of a group of genetic diseases characterized by progressive weakness and degeneration of the skeletal or voluntary muscles that control movement. Abbreviated MD. The muscles of the heart and some other involuntary muscles are also affected in some forms of MD, and a few forms involve other organs as well. The major forms of MD include Duchenne MD, Becker MD, limb-girdle MD, facioscapulohumeral MD, congenital MD, oculopharyngeal MD, distal MD, EmeryDreifuss MD, and myotonic dystrophy. MD can affect people of all ages. Although some forms first become apparent in infancy or childhood, others may not appear until middle age or later. Duchenne MD is the most common kind of MD that affects children. Myotonic dystrophy is the most common kind of MD in adults. There is no specific treatment for any of the forms of MD. Physical therapy to prevent contractures (a condition in which shortened muscles around joints cause abnormal and sometimes painful positioning of the joints), use of orthoses (orthopedic appliances used for support), and corrective orthopedic surgery may be needed to improve the quality of life in some cases. The prognosis with MD depends on the type of MD. Some cases may be mild and very slowly progressive, giving the patient a normal life-span, and other cases may have more marked progression of muscle weakness, functional disability, and loss of ambulation. Life expectancy depends on the degree of progression and late respiratory deficit. In Duchenne MD, death usually occurs in the late teens to early 20s. See also myotonic dystrophy.