Muscular dystrophy (MD) is a group of disorders that cause the body's muscles to become increasingly weak. Muscular dystrophy is an inherited condition.
Types of muscular dystrophy include:
- Duchenne dystrophy — This is the most severe type of muscular dystrophy. It is also the most common. In Duchenne dystrophy, the muscles produce abnormally low levels of dystrophin. Dystrophin is a muscle protein. When dystrophin levels are low, the membranes around muscle cells become weak. They tear easily. Eventually, the muscle fibers die. Duchenne dystrophy primarily affects boys. Women usually do not have symptoms of Duchenne dystrophy. But they can pass it on to their children.
- Becker-type muscular dystrophy — Like Duchenne dystrophy, Becker-type affects dystrophin production and occurs in males. However, the illness is much rarer than Duchenne. And it causes milder symptoms. 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 often start in adolescence.
- 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 and the shoulders is typical. Facioscapulohumeral MD often strikes several members of the same family. However, the symptoms vary in intensity. Family members may have such mild symptoms that they are unaware of any muscle problems.
There are at least two other forms of the illness. These are congenital muscular dystrophy and Emery-Dreifuss dystrophy. Emery-Dreifuss MD causes upper arm and lower leg weakness, and poor heart function. Some forms of congenital muscular dystrophy are associated with decreased mental function.
Symptoms of MD vary according to the specific form of illness. The age of onset varies as well.
- Duchenne dystrophy — Symptoms usually begin between ages 2 and 4. Leg muscles become increasingly weaker. As a result, 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 get larger, even as the legs become weaker. There also is some weakness of arm and neck muscles. But it usually is not as severe as the leg weakness. By age 12, many patients are unable to walk independently and need a wheelchair. In addition, some people with Duchenne dystrophy have mental impairment. They may also have MD-related heart problems.
- Becker-type muscular dystrophy — Symptoms are similar to those of Duchenne dystrophy, but they are milder. They also begin later, usually between ages 5 and 15.
- Myotonic dystrophy — The main symptom is abnormally prolonged muscle contractions and difficulty relaxing the muscles. This is called muscle myotonia. It affects mostly the hands, wrists and tongue. It may develop soon after birth or as late as early adulthood. 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 muscle 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. 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 may begin during infancy, late childhood, or early adulthood. 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.
Your doctor will review your (or your child's) medical history and symptoms. The doctor will ask about the developmental history. This includes age of first sitting, standing, and walking. You will also be asked about history of infections and any significant injuries.
Your doctor will examine you or your child. He or she will look for muscle weakness, wasting and myotonia.
The doctor will do a neurological examination to look for nerve problems.
To confirm the diagnosis of muscular dystrophy, your doctor may order:
- Blood tests. These measure levels of a particular muscle enzyme.
- A muscle biopsy. A tiny sample of muscle will be removed to be examined in a laboratory.
- An electromyogram (EMG). This test records the electrical activity of muscles.
- A genetic blood test. This checks for specific inherited abnormalities in the genetic material.
The outlook varies according to:
- The type of muscular dystrophy
- How quickly it progresses
Some patients have only mild symptoms with a normal lifespan. Others have severe symptoms and die at a young age.
All forms of muscular dystrophy worsen over time. They persist throughout life.
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 done.
When chest muscles are involved in MD, respiratory therapy may be used to delay breathing problems.
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. Unfortunately, MD increases obesity risk because physical limitations prevent people with MD from exercising.
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 children with Duchenne dystrophy, corticosteroids may temporarily keep the illness from getting worse. However, some people cannot tolerate this medication.
Powerful medications that suppress the immune system may help some patients. But their use is controversial and somewhat risky.
In patients with myotonic dystrophy, muscle contractions can be treated with medications.
There is no way to prevent muscular dystrophy.
Genetic testing can help determine the chances of having a child with MD. This usually consists of a simple blood test.
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