Muscle Diseases - Muscular dystrophy

Muscular dystrophy (MD) is defined as an inborn degenerative disease of the muscles. Several varieties of MD have been described and classified according to the muscles involved and the pattern of inheritance. There is no specific treatment for any form of MD, but the patient's life can be made more pleasant and probably prolonged if careful attention is paid to good nutrition, activity without overfatigue, and avoidance of infection. Physical therapists can be helpful in instructing the patient or the parents in an exercise program that relieves joint and muscle stiffness. Sound, prudent psychological support and guidance cannot be overemphasized.

Duchenne's Muscular Dystrophy

In 1886, Dr. Guillaume Duchenne described a muscle disease characterized by weakness and an increase in the size of the muscles and the supporting connective tissue of those muscles. He named the disease pseudohypertrophic (false enlargement) muscular paralysis , but it is now known as Duchenne's muscular dystrophy .

Duchenne's MD is observed almost entirely in males. It is inherited, however, like many other sex-linked anomalies, through the maternal side of the family. The mother can pass the clinical disease to her son; her daughters will not demonstrate the disease but are potential carriers to their sons. More than one-quarter of the cases of Duchenne's MD are sporadic, that is, without any known family history of the disease. There are rare cases of Duchenne's MD in females who have ovarian dysgenesis , a condition in which normal female chromosomal makeup is lacking.

The disease process in Duchenne's MD may be apparent during the first few years of life when the child has difficulty in walking or appears clumsy. The muscles of the pelvis and legs are usually affected first, but the shoulders and the arms soon become involved. About 90 percent of the patients have some enlargement of a muscle or group of muscles and appear to be rather muscular and strong; however, as the disease progresses, the muscular enlargement disappears. Most patients progressively deteriorate and at the age of about 10 to 15 are unable to walk. Once the child is confined to a wheel-chair or bed, there is a progressive deformity with muscle contracture, with death usually occurring toward the end of the second decade. A small percentage of patients appear to have a remission of the disease process and survive until the fourth or fifth decade. Despite herculean attempts to unravel the riddle of muscular dystrophy, the problem is yet unsolved.

A benign variety of MD, Becker type , begins at 5 to 25 years of age and progresses slowly. Most of the reported patients with Becker type are still able to walk 20 to 30 years after the onset of the disease.

Facio-Scapulo-Humeral Muscular Dystrophy

This type of muscular dystrophy affects males and females equally and is thought to be inherited as a dominant trait. The onset may be at any age from childhood to adult life, but is commonly first seen in adolescence. There is not false enlargement of the muscles. The muscles affected, as indicated by the name of the disease, are those of the face and shoulders, usually with abnormal winging of the scapula (either of the large, flat bones at the backs of the shoulders). There is also a characteristic appearance of lip prominence, as if the patient were pouting. Occasionally there is an involvement of the anterior leg muscles and weakness in raising the foot. The disease progresses more slowly than Duchenne's type, and some patients can remain active for a normal life span.

Limb-Girdle Muscular Dystrophy

This type of muscular dystrophy is less clearly delineated than the others. Males and females are equally affected and the onset is usually in the second or third decade, but the process may start later. It is probably inherited as a recessive trait, but many-cases are sporadic. It may first affect the muscles of the pelvis or the shoulder, but in 10 to 15 years both pelvis and shoulder girdles are usually involved. The disease varies considerably from patient to patient; sometimes the disease process appears to be arrested after involvement of either the pelvis or the shoulder, and the course thereafter may be a benign one. Most, however, have significant difficulty in walking by middle age.

Other Varieties of Muscular Dystrophy

These include ocular, oculopharyngeal, and a distal form (involving the muscles of the hands or feet).

Ocular MD

This type involves the muscles that move the eye as well as the eyelids; occasionally, the small muscles of the face and the shoulder girdle are affected.

Oculopharyngeal MD

This type involves not only the muscles that move the eye and the eyelids but may also affect the throat muscles, so that patients have difficulty in swallowing food ( dysphagia ).

Distal MD

This type is rare in the United States but has been reported in Scandinavia. Both sexes can be affected. Usually after the fifth decade, the patient recognizes weakness of the small muscles of the hands and anterior leg muscles that assist in raising the toes. The disease is relatively benign and progresses slowly.