There are over 30 forms if muscular dystropy, all caused by genetic defects in the molecular machinery that helps muscles move. It affects an estimated 1 of every 5,600 to 7,700 boys.
Muscular Dystrophy Overview
Muscular dystrophy (MD) is a group of more than 30 inherited diseases that cause muscle weakness and muscle loss. Muscular dystrophies are caused by genetic defects.
Different types of muscular dystrophy affect specific groups of muscles, have a specific age when signs and symptoms first appear, vary in the severity, and are caused by imperfections in different genes. The most common form of MD is called Duchenne MD and primarily affects boys typically between 3 and 5 years old. The muscles of the upper arms and upper legs usually show weakness first. Most boys are unable to walk by age 12, and later need a respirator to breathe.
Muscular dystrophy (MD) can run in the family, or a person might be the first one in their family to have the condition. Muscular dystrophies are caused by genetic defects in the genes that make muscle proteins.
There is no cure for muscular dystrophy (MD). Treatments for symptoms and preventing complications include physical, respiratory, occupational, and speech therapy, orthopedic devices, assistive technology, corrective surgery, and medications. Medications that can slow or control the symptoms of MD include corticosteroids, anticonvulsants, immunosuppressants, and antibiotics.
Muscular Dystrophy Symptoms
Different types of muscular dystrophy affect specific groups of muscles, have a specific age when signs and symptoms first appear, vary in the severity, and are caused by imperfections in different genes.
- Duchenne MD is the most common form of MD and primarily affects boys. Onset of this type is typically between 3 and 5 years and the disorder progresses rapidly. The muscles of the upper arms and upper legs usually show weakness first. Other parts of the body that can be affected include the brain, throat, heart, chest muscles, diaphragm, stomach, intestines, and spine. Most boys are unable to walk by age 12, and later need a respirator to breathe.
- Becker MD is very similar to Duchenne MD but symptoms are less severe than Duchenne MD. Compared with Duchenne MD, the age of onset for Becker MD is usually later (between 7 and 12 years of age).
- Facioscapulohumeral MD usually begins in the teenage years. It equally affects males and females. The muscles of the face, shoulders, upper arms, and lower legs usually show weakness first. Other parts of the body that can be affected include the eyes, ears, heart, and trunk. Facioscapulohumeral MD progresses slowly and can vary in symptoms from mild to disabling.
- Myotonic MD is the disorder's most common adult form. It usually begins between ages 10 and 30, but onset ranges from birth to 70 years of age. It equally affects males and females. The muscles of the face, neck, arms, hands, hips, and lower legs usually show weakness first. Other parts of the body that can be affected include the eyes, throat, heart, stomach, intestines, hormone producing organs, nerves, and skin. Myotonic MD is characterized by prolonged muscle spasms, cataracts, cardiac abnormalities, and endocrine disturbances. Individuals with myotonic MD have long, thin faces, drooping eyelids, and a swan-like neck.
- Limb-Girdle MD symptoms can appear in childhood but most often appear in adolescence of young adulthood. However, onset ranges from early childhood to late adulthood. Males and females are equally likely to be affected. The muscles of the shoulders and hips usually show weakness first. Other parts of the body that can be affected include the heart, chest muscles, diaphragm, and spine. Limb-girdle MD can progress quickly or slowly, but most patients become severely disabled within 20 years of developing the disease.
- Emery-Dreifuss MD symptoms usually begin by age 10 but can appear in patients up to their mid-20s and is more common in males. The muscles of the upper arms and lower legs usually show weakness first. Other parts of the body that can be affected include the heart and spine. Those with Emery-Dreifuss MD often develop heart problems by age 30.
- Distal MD symptoms usually begin between ages 40 and 60. Males and females are equally likely to be affected. The muscles of the lower arms, hands, lower legs, and feet usually show weakness first. Other muscles may be affected. Distal MD is less severe and progresses more slowly than other forms of MD. Patients may eventually need a ventilator.
- Oculopharyngeal MD symptoms usually appear later in life, after about 40 years of age. Males and females are equally likely to be affected. The muscles of the face (especially around the eyes), neck, upper arms, and upper legs usually show weakness first. The throat may also be affected.
- Congenital MD muscle weakness typically begins at birth or in early infancy. Males and females are equally likely to be affected. The muscles of the neck, arms, trunk, and legs usually show weakness first. Other parts of the body that can be affected include the brain, eyes, throat, heart, diaphragm, chest muscles, and spine. Some patients die in infancy, but others live into adulthood with only mild disability.
Muscular Dystrophy Causes
Muscular dystrophies are a group of diseases caused by defects in a person’s genes.
Muscular dystrophy (MD) can run in the family, or a person might be the first one in their family to have the condition. There are a number of different types of MD. Here are a few of the most common forms of MD:
- Duchenne MD is caused by the absence of dystrophin, a protein involved in maintaining the integrity of muscle. Girls in these families have a 50 percent chance of inheriting and passing the defective gene to their children.
- Becker MD is caused by a faulty or not having enough dystrophin rather than an absence of dystrophin.
- Facioscapulohumeral MD is caused by a genetic defect. While researchers know where the defect occurs, it is unknown what gene causes Facioscapulohumeral MD.
- Myotonic MD appears in two forms, type 1 and type 2. Type 1 is more common and is caused by an abnormally large number of repeats of a three-letter "word" (CTG) in genetic code. (While most people have up to 37 repeats of CTG, people with myotonic can have up to 4,000. The number of repeats may reflect the severity of symptoms.)
- Limb-Girdle MD has several different types which are caused by different gene mutations. Patients with limb-girdle MD inherit a defective gene from either parent, or, in the more severe form, the same defective gene from both parents.
- Emery-Dreifuss MD has two forms that are caused by defects in certain proteins.
- Distal MD is caused by defects in dysferlin.
- Oculopharyngeal MD is caused by a defect in a protein that binds to molecules that help make other proteins. It is common among Americans of French-Canadian descent, Jewish Ashkenazi, and Hispanics from the Southwest region.
- Congenital MD is commonly caused by a defect in the protein merosin, which surrounds muscle fibers.
MD is not contagious and cannot be caused by injury or activity.
Muscular Dystrophy Diagnosis
Doctors may order tests to determine whether the problems are a result of MD and, if so, what form of this disorder. The tests may also rule out other problems that could cause muscle weakness, such as surgery, toxic exposure, medications, or other muscle diseases. These tests may include:
- Blood tests to measure levels of enzymes such as serum creatine kinase and serum aldolase. Elevated levels of either of these enzymes can signal muscle weakness and indicate a need for additional testing.
- Muscle biopsies, in which a sample of muscle tissue is then examined under a microscope to provide information on the amount and level of the genes that may cause MD.
- Genetic testing to evaluate missing or repeated mutations in the dystrophin gene. The test is important not only to confirm the MD diagnosis in males but also to determine whether women with a family history of Duchenne or Becker MD may be carriers.
- Neurological tests to rule out other nervous system disorders, to identify patterns of muscle weakness and wasting, to test reflexes and coordination, and to detect contractions.
- Imaging tests such as magnetic resonance imaging (MRI) and ultrasound imaging to examine muscle quality and bulk as well as the fatty replacement of muscle tissue.
Your doctor may also order tests to look at your heart and assess your exercise ability.
Doctors may ask about the patient’s family history and medical history, including any problems affecting the muscles that the patient may be experiencing.
Living With Muscular Dystrophy
Advances in drug therapies, physical therapies, and assistive technologies can help to make some daily activities easier to further improve health and quality of life.
Almost all people with any form of MD experience a worsening of symptoms over time. Typically, muscles weaken over the life course, and patients may have greater difficulty performing tasks as they age.
Some ways that patients and their families can overcome the challenges of the disorder include:
- Making the environment accessible by ensuring access for devices such as wheelchairs that aid with mobility.
- Improving mobility by using braces, crutches, wheelchairs, and electric scooters.
- Maintaining a healthy weight is an important way to reduce added stress on muscles and to prevent certain health conditions, such as respiratory problems.
- Low-impact physical activity like swimming can help improve muscle strength and overall well-being.
- Getting restful sleep. If finding a comfortable position to sleep becomes an issue, there are certain beds, pads, and mattresses that can help improve comfort, and in turn can improve the quality of sleep.
Those with MD and their families may also benefit from getting involved with support groups and local organizations.
Muscular Dystrophy Treatments
There is no cure for muscular dystrophy (MD). However, there are treatments that can help with the symptoms and prevent complications. They include physical, respiratory, occupational, and speech therapy, orthopedic devices, assistive technology, corrective surgery, and medications.
Some patients may need assisted ventilation to treat respiratory muscle weakness and a pacemaker for cardiac abnormalities.
Some medications that can slow or control the symptoms of MD include:
- corticosteroids to increase muscle strength, increase respiratory function, and to slow muscle degeneration
- anticonvulsants to control seizures and some muscle activity
- immunosuppressants to delay some damage to dying muscle cells
- antibiotics to treat respiratory infections
Muscular Dystrophy Other Treatments
The National Institute of Neurological Disorders and Stroke (NINDS) supports a broad program of research studies on muscular dystrophy. The goals of these studies are to understand muscular dystrophy and to develop techniques to diagnose, treat, prevent, and ultimately cure the disorder.