Muscular dystrophy
- Reviewed by Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
What is muscular dystrophy?
Muscular dystrophy (MD) is a group of inherited disorders that cause the body's muscles to become increasingly weak. MD develops due to abnormal genes involved in muscle function.
Types of muscular dystrophy include:
- Duchenne dystrophy. This is the most common and most severe type of muscular dystrophy. In Duchenne dystrophy, the muscles produce abnormally low levels of dystrophin, a muscle protein. When dystrophin levels are low, the membranes around muscle cells become weak. They tear easily, leading to the muscle fibers' death. Duchenne dystrophy primarily affects boys, but women can carry the abnormal gene and pass it on to their children.
- Becker muscular dystrophy. Like Duchenne dystrophy, Becker MD affects dystrophin production and mostly affects males. However, Becker MD is much rarer, causes milder symptoms, and onset of symptoms begins later (see below). Heart muscle involvement may be a major feature. Some people have a form of disease that falls in between Duchenne and Becker-type.
- Myotonic dystrophy. Myotonic dystrophy can occur in men and women. It is the most common form of adult MD. Symptoms are highly variable; onset may occur during infancy or at advanced age.
- Limb-girdle muscular dystrophy. Limb-girdle MD affects muscles of the shoulders and hips. It includes several different illnesses. It can be inherited by both males and females.
- Facioscapulohumeral muscular dystrophy. This form of MD occurs in males and females. Weakness of the facial muscles, shoulders, and hips is typical. Facioscapulohumeral MD often strikes several members of the same family. However, the symptoms tend to vary in intensity. Family members may have such mild symptoms that they are unaware of any muscle problems.
- Emery-Dreifuss muscular dystrophy. This condition typically causes symptoms in early childhood, causing upper arm and lower leg weakness, and poor heart function.
- Congenital muscular dystrophies. These disorders are diagnosed within the first two years of life (and often at the time of birth). They typically cause muscle weakness and contractures (severe joint stiffness due to shortening of muscles, tendons, or skin). Some forms of these conditions cause abnormal brain development, decreased cognitive function, seizures, and eye problems.
- Oculopharyngeal muscular dystrophy. This rare form of MD causes drooping of the eyelids and weakness of throat muscles leading to impaired speech and swallowing.
- Distal muscular dystrophies. This is a group of disorders that initially cause weakness of the hands, wrists, and/or lower legs (andamp;ldquo;distal” means far from the center of the body). Typical onset of symptoms is between the ages of 40 and 60.
Symptoms of muscular dystrophy
Symptoms of MD vary according to the specific form of illness. The age of onset varies as well. Below is a list of some of the more common forms of MD and the symptoms they cause.
- Duchenne dystrophy. Symptoms usually begin between the ages of 2 and 4 and typically include thigh and shoulder weakness. As a result of leg muscle weakness, the child tends to fall frequently and has difficulty getting up from the ground, walking, or running normally. The calf muscles gradually get larger, even as the legs become weaker. There are also often weakness of neck muscles as well, though usually not as severe as the leg weakness. By age 12, many patients are unable to walk independently and need a wheelchair; it is rare that affected individuals survive past age 30. In addition, some people with Duchenne dystrophy have cognitive impairment, scoliosis, and heart problems.
- Becker-type muscular dystrophy. Symptoms are similar to those of Duchenne dystrophy, but they are usually milder and begin later (between ages 5 and 15).
- Myotonic dystrophy. The main symptom is muscle myotonia — abnormally prolonged muscle contractions and difficulty relaxing the muscles. It affects mostly the hands, wrists, and tongue. It may develop in all groups, from infancy to advanced age. There also is wasting and weakening of facial muscles, neck muscles, and muscles of the wrists, fingers, and ankles. If the tongue and throat muscles are involved, the patient can have speech problems and difficulty swallowing. If the diaphragm and chest muscles are involved, there may be breathing problems. Other problems include cognitive and behavioral challenges, cataracts, and abnormal heart rhythms.
- Limb-girdle muscular dystrophy. Symptoms may begin in early childhood or adulthood. They include progressive muscle weakness in the shoulders, pelvis, or both. Breathing problems occur if the diaphragm is involved. If the illness affects the heart muscle, there may be heart failure or abnormal heart rhythms.
- Facioscapulohumeral muscular dystrophy. Symptoms tend to begin between the ages of 10 and 20, though earlier onset may occur. Usually the first sign is facial weakness. There is difficulty smiling, whistling, and closing the eyes. Later there is difficulty raising the arms or flexing the wrists and/or ankles. Other problems include vision and hearing loss, impaired cognition, seizures, and abnormal heart rhythms.
Diagnosing muscular dystrophy
Your doctor will review your (or your child's) medical history and symptoms. The doctor will ask about developmental history. This includes various milestones such as age when first able to sit, stand, and walk. You will also be asked about history of infections and any significant injuries.
Your doctor will examine you or your child, looking for muscle weakness, wasting, and myotonia.
The doctor will perform a neurological examination to look for nerve problems.
To confirm the diagnosis of muscular dystrophy, your doctor may order
- blood tests that measure levels of a particular muscle enzyme and can detect genetic abnormalities
- a muscle biopsy, in which a tiny sample of muscle will be removed to be examined in a laboratory
- an electromyogram (EMG), a test that records the electrical activity of muscles.
Expected duration of muscular dystrophy
All forms of muscular dystrophy tend to worsen over time and persist throughout life.
Preventing muscular dystrophy
When MD occurs due to a spontaneous mutation — that is, when the mutation is not inherited but instead occurs during fetal development — the condition cannot be prevented.
For inherited forms of MD, genetic testing can help determine the chances of having a child with MD. Some people who learn that they carry a gene mutation linked to muscular dystrophy elect to adopt, pursue fertility interventions that can avoid having a child with MD, or forego parenthood.
Treating muscular dystrophy
There is no cure for muscular dystrophy and no way to stop it from getting worse. Patients are given supportive care, leg braces, and physiotherapy to help them function in daily life.
It's particularly important that limbs be stretched. This helps prevent tightened tendons and muscles. When tightness of tendons (contractures) develops, surgery can be performed. Despite limitations related to muscle weakness, regular exercise is recommended.
When chest muscles are involved in MD, respiratory therapy may be used to delay breathing problems. Assisted ventilation is commonly necessary for many types of MD.
Mental health assessment and care, attention to bone health, and fall prevention measures are routine parts of MD treatment.
People with MD are also given age-appropriate dietary therapy. This helps prevent obesity. Obesity is especially harmful to patients with muscular dystrophy. It places additional strain on their weak muscles.
Some forms of MD involve the heart. Patients with these forms should have their heart function and rhythm evaluated. Medications to improve heart function and rhythm may be helpful. A pacemaker can help to maintain a normal heart rate.
In boys with Duchenne dystrophy, corticosteroids may temporarily keep the illness from getting worse. However, some people cannot tolerate this medication.
Genetic treatments such as eteplirsen, golodirsen, or viltolarsen may be recommended for Duchenne dystrophy if certain genetic mutations are present.
In patients with myotonic dystrophy, muscle contractions can be treated with medications such as mexiletine.
When to call a professional
Call your doctor if you notice muscle weakness anywhere in your body. Also call if 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
- trouble getting up from the ground
- trouble walking
- trouble running.
Prognosis
The outlook varies widely depending on the type of muscular dystrophy and how quickly it progresses.
Some patients have only mild symptoms with a normal lifespan. Others have severe symptoms and die at a young age.
Additional info
National Institute of Neurological Disorders and Stroke
http://www.ninds.nih.gov/
Muscular Dystrophy Association
http://www.mdausa.org/
Parent Project for Muscular Dystrophy Research
http://www.parentdmd.org/
About the Reviewer
Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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