What is Muscular Dystrophy?
Muscular dystrophy (MD) is a group of rare inherited muscle diseases in which muscle fibers are unusually susceptible to damage. Muscles, primarily your voluntary muscles, become progressively weaker. In the late stages of muscular dystrophy, fat and connective tissue often replace muscle fibers. In some types of muscular dystrophy, heart muscles, other involuntary muscles and other organs are affected. There are many forms of muscular dystrophy, some noticeable at birth (congenital muscular dystrophy), others in adolescence (Becker MD), but the 3 most common types are Duchenne, facioscapulohumeral, and myotonic. The various types of the disease affect more than 50,000 Americans. There's no cure, but medications and therapy can slow the course of the disease.
Duchenne MD - primarily affects boys and is the result of mutations in the gene that regulates dystrophin - a protein involved in maintaining the integrity of muscle fiber. Onset is between 3-5 years and progresses rapidly. Most boys become unable to walk at 12, and by 20 have to use a respirator to breathe.
Becker-type muscular dystrophy - Like Duchenne dystrophy, Becker-type muscular dystrophy is linked to the X chromosome, affects dystrophin production, and occurs in males. However, the illness is about 10 times rarer than Duchenne, and it produces milder symptoms. Some people seem to have a form of disease that is intermediate in severity between Duchenne and Becker-type.
Facioscapulohumeral MD - appears in adolescence and causes progressive weakness in facial muscles and certain muscles in the arms and legs. It progresses slowly and can vary in symptoms from mild to disabling.
Limb-girdle muscular dystrophy - This form of muscular dystrophy affects muscles of the shoulders and hips. It includes several different illnesses, which can be inherited by both males and females.
Myotonic MD - varies in the age of onset and is characterized by myotonia (prolonged muscle spasm) in the fingers and facial muscles; a floppy-footed, high-stepping gait; cataracts; cardiac abnormalities; and endocrine disturbances. Individuals with myotonic MD have long faces and drooping eyelids; men have frontal baldness.
Symptoms of muscular dystrophy, as well as their age of onset, vary according to the specific form of illness:
- Duchenne dystrophy - Signs and symptoms of Duchenne's usually appear between the ages of 2 and 5. It first affects the muscles of the pelvis, upper arms and upper legs. By late childhood, most children with this form of muscular dystrophy are unable to walk. Most die by their late teens or early 20s, often from pneumonia, respiratory muscle weakness or cardiac complications. Some people with Duchenne's MD may exhibit curvature of their spine (scoliosis).
- Becker-type muscular dystrophy - Signs and symptoms of Becker's MD are similar to those of Duchenne's. The onset of the signs and symptoms is generally later, from age 5 to 16
- Myotonic dystrophy - Muscle myotonia (abnormally prolonged muscle contraction, with difficulty relaxing) may develop soon after birth or begin as late as early adulthood, especially affecting the hands, wrists and tongue. There also is wasting and weakening of facial muscles, neck muscles, and muscles of the wrists, fingers and ankles. Involvement of the tongue and throat muscles causes speech problems and difficulty swallowing. If the diaphragm and chest muscle also are involved, there may be breathing problems.
- Limb-girdle muscular dystrophy - Symptoms begin in late childhood or early adulthood. They include progressive muscle weakness in the shoulders and hips, together with breathing problems (if the diaphragm is involved). If illness also affects the heart muscle, there may be heart failure or abnormal heart rhythms.
- Facioscapulohumeral muscular dystrophy - Symptoms may begin during infancy, late childhood, or early adulthood. Usually, the first sign is facial weakness, with difficulty smiling, whistling and closing the eyes. Later, there is difficulty raising the arms or flexing the wrists and/or ankles.
What Causes Muscular Dystrophy?
Muscular dystrophy is a general term for a group of inherited diseases involving a defective gene. Each form of muscular dystrophy is caused by a genetic mutation that's particular to that type of the disease.
Duchenne's and Becker's muscular dystrophies are passed from mother to son through one of the mother's genes in a pattern called X-linked recessive inheritance. Boys inherit an X chromosome from their mother and a Y chromosome from their father. The X-Y combination makes them male. Girls inherit two X chromosomes, one from their mother and one from their father. The X-X combination determines that they are female.
The defective gene that causes Duchenne's and Becker's muscular dystrophies is located on the X-chromosome. Women who have the defective gene that causes these muscular dystrophies are simply carriers and exhibit no signs or symptoms of the disease. The disease can "skip" a generation until another son inherits the defective gene on the X-chromosome. In some cases of Duchenne's and Becker's muscular dystrophies, the disease arises from a new mutation in a gene rather than from an inherited defective gene.
Myotonic dystrophy is passed along in a pattern called autosomal dominant inheritance. If either parent carries the defective gene for myotonic dystrophy, there's a 50 percent chance the disorder will be passed along to a child.
Some of the less common types of muscular dystrophy are passed along in the same inheritance pattern that marks Duchenne's and Becker's muscular dystrophies. Other types of muscular dystrophy can be passed on from generation to generation and affect males and females equally. Still others require a defective gene from both parents.
Treatments for Muscular Dystrophy
There is no cure for muscular dystrophy, although some drugs still in the trial stage have shown promise in slowing or delaying the progression of the disease. For the time being, treatment is aimed at preventing complications due to the effects of weakness, decreased mobility, contractures, scoliosis, heart defects and respiratory weakness.
Physical therapy: Physical therapy, especially regular stretching, is important in helping to maintain the range of motion for affected muscles and to prevent or delay contractures. Strengthening other muscles to compensate for weakness in affected muscles may be of benefit also, especially in earlier stages of milder MD. Regular exercise is important in maintaining good, overall health, but strenuous exercise may damage muscles further. For patients whose leg muscles are affected, braces may help lengthen the period of time that they can walk independently.
Medications: Doctors prescribe medications to treat some forms of muscular dystrophy:
- For myotonic dystrophy. The medications phenytoin (Dilantin, Phenytek), quinine and procainamide (Pronestyl) may be used to treat the delayed muscle relaxation that occurs in myotonic dystrophy.
- For Duchenne's muscular dystrophy. The anti-inflammatory corticosteroid medication prednisone (Deltasone) may help improve muscle strength and delay the progression of Duchenne's MD.
Occupational therapy: Occupational therapy involves employing methods and tools to compensate for a patient’s loss of strength and mobility. This may include modifications at home, dressing aids, wheelchair accessories and communication aids.
Nutrition: Nutrition has not been shown to treat any conditions of MD, but it is essential to maintaining good health.
Cardiac care: Arrhythmias are often a symptom with Emery-Dreifuss and Becker MD and may need to be treated with special drugs. Pacemakers may also be needed in some cases and heart transplants are becoming more common for men with Becker MD.
Respiratory care: When the muscles of the diaphragm and other respiratory muscles become too weak to function on their own, a patient may require a ventilator to continue breathing deeply enough. Air may also be administered through a tube or mouthpiece. It is therefore very important to maintain healthy lungs to reduce the risk of respiratory complications.
Surgery: To release the contractures that may develop and that can position joints in painful ways, doctors can perform a tendon release surgery. This may be done to relieve tendons of your hip and knee and on the Achilles tendon at the back of your foot. Surgery may also be needed to correct curvature of your spine.
MD Caregiver Well-Being
For family members of people with muscular dystrophy, coping with the illness involves a major commitment of physical, emotional and financial effort. The disease presents challenges in the classroom, in the home and in all aspects of life.
In dealing with a disease such as muscular dystrophy, support groups can be a valuable part of a wider network of social support that includes health care professionals, family, friends and place of religious worship.
Support groups bring together people, family and friends who are coping with the same kind of physical or mental health challenge. Support groups provide a setting in which people can share their common problems and provide ongoing support to one another.
Ask your doctor about self-help groups that may exist in your community. Your local health department, public library, telephone book and the Internet also may be good sources to locate a support group in your area.
|The Muscular Dystrophy Association |
3300 E. Sunrise Drive
Tucson, AZ 85718
|Muscular Dystrophy Family Foundation |
615 North Alabama Street Suite 330
Indianapolis IN 46204-1213