Muscular dystrophy (MD) is a group of over 30 inherited conditions that cause progressive weakness and loss of muscle mass. While there is no cure for MD, treatments can help manage symptoms and slow progression.
Genetic changes cause MD. These mutations change how the body produces and maintains healthy muscle tissue.
MD is more prevalent in males than females. The most common form, Duchenne muscular dystrophy (DMD), affects approximately 1 in 3,500 male births. Although it typically affects young children, other variations can appear in adulthood.
Currently, there is no cure for MD. Physical therapy and certain medications can slow its progression and improve a person’s quality of life. Researchers are working on developing gene therapies that may provide hope for people with certain types of MD.
Read more to learn about the different types of MD, what causes it, and how people can manage it.
What is muscular dystrophy?
MD is a group of over 30 conditions that lead to muscle weakness and degeneration. As the condition progresses, it becomes harder to move. It can affect breathing and heart function, which can be life threatening.
Depending on the type and severity of a person’s MD, the effects can be mild, progressing slowly over an average life span. In other cases, it can be aggressive, progressing quickly and shortening a person’s life.
There is currently no way to prevent or reverse MD. However, different kinds of therapy and drug treatment can improve a person’s quality of life and delay the progression of symptoms.
Symptoms
Although there are many types of MD, DMD is the most common. This section will cover DMD’s symptoms, but the symptoms of each kind of MD can differ.
Early symptoms can include:
- a waddling gait
- pain and stiffness in the muscles
- difficulty running and jumping
- walking on the toes
- difficulty sitting up or standing
- learning disabilities, such as developing speech later than usual
- frequent falls
As the disease progresses, the following symptoms become more likely:
- inability to walk
- a shortening of muscles and tendons, further limiting movement
- breathing problems that may require assisted breathing
- curvature of the spine if the muscles are not strong enough to support its structure
- weakening of the heart muscles, leading to cardiac problems
- difficulty swallowing, with a risk of aspiration pneumonia
Treatment
Currently, there is no cure for MD. Medications and various therapies can slow the progression of the condition and improve a person’s mobility.
Drugs
Various medications can treat MD. A doctor may prescribe:
- corticosteroids
- anticonvulsants
- immunosuppressants
If a person has DMD, they may receive injections of drugs that target certain genes. People with DMD have a mutation in the gene that produces dystrophin, a protein that protects and builds muscle tissue. Individuals with specific gene mutations may be eligible for this gene therapy, and researchers are working to develop new gene therapies that can halt or reverse muscle loss.
Physical therapy
The following therapies may help an individual living with MD:
- Physical therapy: Mobility and stretching exercises can help combat the tightening of muscles and tendons, also known as contractures. Standard low impact aerobic exercises like walking and swimming can also help slow the progression of symptoms.
- Breathing assistance: As the muscles used for breathing become weaker, a person may need devices to help them breathe while they sleep. In severe cases, they may need to use a ventilator.
- Mobility aids: Canes, wheelchairs, and walkers can help a person stay mobile.
- Braces: These keep muscles and tendons stretched, slowing their shortening.
Recent research
Although experts do not yet have a cure for MD, ongoing research into various therapies may provide hope.
Gene replacement therapy
Researchers have found the specific gene involved in MD. Therefore, a replacement geneTrusted Source to create missing dystrophin protein may help treat people with MD.
However, there are challenges with this approach, including the potential for the immune system to reject a new protein and the large size of the dystrophin gene. There are also difficulties in delivering the new gene directly to the skeletal muscle.
Drugs to delay muscle wasting
Rather than target the genes causing MD, some researchers are attempting to slow the progressive muscle wasting.
In normal conditions, muscles can repair themselves. Research into controlling or increasing these repairs could benefit some people with MD.
Stem cell research
Researchers are analyzing the possibility of using muscle stem cells to treat MD. Current projects are looking at the most useful type of cells to use and ways that doctors could deliver them to skeletal muscle.
Myoblast transplantation
During the early stages of MD, a type of stem cell called myoblasts repair and replace faulty muscle fibers. Once the myoblasts wear out, the muscles slowly turn into connective tissue.
Some studies have attempted to insert modified myoblast cells into muscles to take over from the exhausted natural myoblasts.
Types
Although the most common type of MD is DMD, there are several different types. These can occur at different stages of life, and they progress at different rates. Types of MD include:
- DMD: Caused by mutations in the dystrophin gene, symptoms of this normally start before age 3. It causes progressive muscle loss, and most children with the condition use a wheelchair by age 12.
- Becker (BMD): Dystrophin gene mutations also cause BMD. It is similar to DMD, but progresses more slowly and appears later.
- Myotonic (MMD or Steinert’s disease): This is the most common adult-onset form, and it usually appears between 20–30. It prevents muscles from relaxing once they contract and often begins with the face and neck muscles.
- Congenital (CMD): This type appears from birth to age 2 and affects all genders. Some forms progress slowly, while others can move rapidly and cause significant disability.
- Limb-girdle (LGMD): This MD begins in childhood or the teenage years. Individuals with the limb-girdle MD might have trouble raising the front part of the foot, making tripping a common problem.
- Oculopharyngeal (OPMD): This usually appears after age 40. It affects the eyelids, throat, and face first, then the shoulders and pelvis.
Causes
Genetic changes cause MD, and each type is due to a different set of mutations. However, all the mutations prevent the body from producing dystrophin, a protein essential for building and repairing muscles.
Although dystrophin makes up a small percent of the total proteins in muscles, it is an essential molecule for their normal function. It glues various parts of muscle tissue together and links them to the sarcolemma, or the outer membrane.
If dystrophin is absent or deformed, this process does not work correctly. This weakens the muscles and can damage the muscle cells.
In DMD, dystrophin is almost entirely absent. Conversely, in BMD, dystrophin is smaller or in short supply.
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Diagnosis
Doctors can use various tests to diagnose MD:
- Enzyme assay: Damaged muscles produce creatine kinase (CK). Elevated levels of CK without other types of muscle damage could suggest MD.
- Genetic testing: Doctors can screen for the genetic mutations that occur in MD.
- Heart monitoring: Electrocardiography and echocardiograms can detect changes in the muscle of the heart. This is especially useful for diagnosing myotonic MD.
- Lung monitoring: Checking lung function can provide additional information.
- Electromyography: A doctor places a needle into the muscle to measure electrical activity. The results can show signs of muscle disease.
- Biopsy: Removing a portion of the muscle and examining it under a microscope can show signs of MD.
Outlook
The life expectancy of people with MD depends on the type and symptom severity.
In the past, people with DMD typically did not live beyond their 20s. However, new treatment options are increasing the average lifespan.
Currently, the average life expectancy for people with DMD is 31 years, but this depends on if the individual has mechanical ventilatory support as the disease progresses. Life expectancy has improved with medical advances, and many people with DMD can expect to age 40 and beyond.