What Is It?
Muscular dystrophy refers to a group of genetic (inherited) conditions that cause progressive deterioration of the body’s muscles, with increasing weakness and disability. These include:
- Duchenne dystrophy (pseudohypertrophic muscular dystrophy) — This type of muscular dystrophy is caused by a defective gene (segment of DNA) inherited on the X chromosome. It primarily affects boys and is the most severe type. Although women with the defective gene are carriers, they usually do not show symptoms. In Duchenne dystrophy, the defective gene causes muscles to produce abnormally low levels of a muscle protein called dystrophin. When dystrophin levels are low, the membranes around muscle cells become weak and tear easily, eventually leading to death of muscle fibers. Duchenne dystrophy is the most common form of muscular dystrophy, occurring in one out of every 3,000 male newborns.
- 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.
- Myotonic dystrophy — This form of muscular dystrophy can occur in both sexes and is the most common form of adult muscular dystrophy, with symptoms often starting in adolescence.
- 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.
- Facioscapulohumeral muscular dystrophy — This form of muscular dystrophy occurs in both sexes, and it often strikes several members of the same family. However, because the symptoms vary in intensity, family members may have such mild forms of the illness that they are unaware of any muscle problems. Weakness of the facial muscles and the shoulder is typical.
In addition, there are two other forms of the illness that are fairly rare: congenital muscular dystrophy and humeroperoneal muscular dystrophy (Emery-Dreifuss dystrophy). Some forms of congenital muscular dystrophy are associated with decreased mental function, whereas humeroperoneal muscular dystrophy causes upper arm and lower leg weakness, as well as poor heart function.
Symptoms of muscular dystrophy, as well as their age of onset, vary according to the specific form of illness:
- Duchenne dystrophy — Symptoms usually begin between ages 2 and 4. Because of a progressive weakening of leg muscles, the child falls frequently and has difficulty getting up from the ground. The child also has trouble walking or running normally. The calf muscles gradually enlarge, even as the legs become weaker. Although there also is some weakness of arm and neck muscles, this is not usually as severe as the leg weakness. By age 12, most patients are unable to walk and are limited to a wheelchair. As the illness progresses, there also is an abnormal curvature of the spine. In addition, some patients with Duchenne dystrophy suffer from mental impairment or heart problems caused by muscular dystrophy-related damage to heart muscle.
- Becker-type muscular dystrophy — Symptoms are similar to those of Duchenne dystrophy, but they are milder and begin later, usually between ages 5 and 15.
- 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.
Your doctor will review the patient’s medical history and symptoms. If the patient is a child, the doctor will ask about your child’s developmental history (age of first sitting, standing, walking), history of infections, and any significant injuries.
Your doctor will examine you, paying special attention to the muscles. He or she will look for muscle weakness, wasting and myotonia and will do a neurological examination to look for nerve problems. To confirm the diagnosis of muscular dystrophy, your doctor may order:
- Blood tests to measure levels of creatine phosphokinase, a muscle enzyme
- A muscle biopsy (removing a tiny sample of muscle to be examined in a laboratory)
- An electromyogram, or EMG (a test that records the electrical activity of muscles)
- A genetic blood test (to check for specific inherited abnormalities in chromosomes)
All forms of muscular dystrophy are progressive and persist throughout life.
The only way to prevent muscular dystrophy is for parents who are carriers of the defective genes not to have children. Genetic testing of potential parents (usually a simple blood test) can help to determine the chances of having a child with the one of these disorders.
There is no cure for muscular dystrophy and no way to stop it from getting worse. In general, patients are given supportive care, together with leg braces and physiotherapy to maximize their ability to function in daily life. Stretching limbs to avoid tightened tendons and muscles is particularly important. When tightness of tendons (contractures) develops, surgery can be performed. When chest muscles are involved, respiratory therapy may be used to delay the onset of breathing problems. In addition, people with muscular dystrophy are given age-appropriate dietary therapy to help them follow a healthy meal plan while avoiding obesity. Obesity is especially harmful to patients with muscular dystrophy because it places additional strain on their already weak muscles. Unfortunately, many muscular dystrophy patients are at a high risk of obesity because their physical limitations prevent them from exercising.
In boys with Duchenne dystrophy, corticosteroids (such as prednisone) may be prescribed to temporarily delay progression of their illness; however, some patients cannot tolerate this medication because of side effects. Powerful medications that suppress the immune system have been reported to help some patients, but their use is controversial and somewhat risky. Other experimental treatments are being developed, including gene therapy, in which abnormal muscular dystrophy genes are replaced with healthy ones, and myoblast-transfer therapy, in which muscle cells from a healthy relative are injected into the muscles of an affected child.
In patients with myotonic dystrophy, myotonia may be treated with medications such as carbamazepine (Tegretol and other brand names) or phenytoin (Dilantin).
When To Call A Professional
If you are an adult, call your doctor if you notice muscle weakness anywhere in your body or if you notice that you have trouble speaking clearly or swallowing normally. If you are a parent, call your child’s physician if your child has unusually frequent falls, has trouble getting up from the ground, or has trouble walking or running.
The prognosis varies according to the type of muscular dystrophy and its progression. Some patients have only mild symptoms with a normal lifespan, whereas others have severe symptoms and die at a young age. For example, boys with Duchenne dystrophy often die before age 18 because of respiratory failure, heart failure, pneumonia or other problems. In boys with Becker-type muscular dystrophy, death tends to occur later.
Most patients with facioscapulohumeral muscular dystrophy have muscle weakness limited to the face, neck and upper body, and their vital functions (heart function and breathing) usually remain unaffected.
Diseases and Conditions Center
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.