Limb-girdle muscular dystrophy

The major types of muscular dystrophy (MD) are Duchenne, limb-girdle, facioscapulohumeral (FSH), Becker, and myotonic. In the United States, 250,000 people are affected by muscular dystrophy, with boys disproportionally represented at the rate of one in every 4,000 births.

Duchenne, the most severe form of muscular dystrophy, is passed exclusively by a defective gene in the mother to her son. A woman with the defective gene has a 50% chance of bearing a son with Duchenne muscular dystrophy. Female children of carrier mothers have a 50% chance of being carriers themselves. In this disease, the muscles of the lower body and spine are affected first; onset is in early childhood between the ages of two and six years. Nearly one-half of all Duchenne victims do not walk until after they reach 18 months old. When they do begin walking, it is usually with a waddling or swaying gait. The child will also have difficulty getting up from the floor or standing on one foot and may tire easily. A child with Duchenne MD has a tendency to walk on the toes, which causes the pelvis to tilt forward, resulting in lordosis, a hollowing of the back. The disease also creates muscle enlargement, especially in the calf. Dental problems, such as a widening of the jaw and spaces between the teeth, are also common. The child's arms are usually not affected until the latter stages of the disease.

Most victims of Duchenne MD lose the ability to walk between the ages of 10 and 13. This will result in bone deformities, scoliosis, and deterioration of the respiratory muscles. The child may also suffer from constipation due to constant sitting. Death usually results from respiratory infection or heart failure. Borderline mental retardation and slowed intellectual development occasionally accompany Duchenne MD. However, many patients have above-average intelligence .

Limb-girdle muscular dystrophy describes a group of diseases that affect the muscles in the pelvic area and manifests itself in late childhood to middle age. Its effects range from mild to debilitating. An early onset of limb-girdle muscular dystrophy usually signals a swift and severe case. It shares the toe walking and muscle enlargement features characteristic of Duchenne. However, the heart and mental development are usually not affected. Limb-girdle MD is passed on to boys when the defective gene is carried by both parents.

Facioscapulohumeral (FSH) muscular dystrophy is a mild form of the disease involving the muscles of the shoulders, upper back, and face. It appears in adolescence, affecting both boys and girls. FSH is inherited from a parent who also suffers from FSH. Victims' face muscles tend to weaken first; they cannot close their eyes tightly, purse their lips to blow, or puff out their cheeks. This is followed by a weakening of the shoulder and upper back muscles, making it difficult for the child to raise his arms, or to lift objects. The shoulder blades push upward towards the head, creating a "terracing" characteristic.

Becker muscular dystrophy is similar to Duchenne in that it is passed to sons from mothers possessing the defective gene. The symptoms are also similar to Duchenne and occur between two and 16 years of age. Victims of Becker MD generally walk until adulthood and live into their 30s and even 50s. Heart complications are rare.

Myotonic dystrophy, also known as Steinert's disease, attacks the eyes, heart, and testes. Its most telling characteristic is the inability of the muscles to relax after sudden, vigorous exertion.

Three laboratory tests are administered to determine the existence of muscular dystrophy. A blood test can pick up proteins leaked by the muscles even before muscle weakness occurs. An electromyogram will register certain tracings if muscles are diseased. A biopsy of muscle tissue can also detect the condition.

Because no cure exists for muscular dystrophy, the focus of parents and medical professionals is to help the patient maintain his mobility as long as possible and to remain an active member of society. The child should be encouraged to exercise the affected muscles, even during periods of illness. Parents should also work closely with teachers to provide a positive educational environment for the child. Time allowances should be made to accommodate the child's difficulty in turning textbook pages, grasping a pencil or pen, and traveling within the classroom and school buildings. Participation in physical education classes should be allowed as much as possible. Even if the child cannot play a particular game, he can keep score or be involved in other ways.

Muscular dystrophy is an extremely difficult challenge for a young person to face, and emotional support is of utmost importance. Summer camps operated by the Muscular Dystrophy Association have been very effective in building self esteem in MD patients. Parents and other family members may find encouragement in joining support groups.

Further Reading

For Your Information

Books

• Corrick, James A. Muscular Dystrophy. New York: F. Watts, 1992.
• Donsbach, Kurt W., and H. Rudolph Alsleben. Multiple Sclerosis, Muscular Dystrophy and ALS. USA: Rockland Corporation, 1993.

Gale Encyclopedia of Childhood & Adolescence. Gale Research, 1998.