Muscular Dystrophy

Overview

Muscular dystrophy is a group of diseases that cause progressive weakness and loss of muscle mass. In muscular dystrophy, abnormal genes (mutations) interfere with the production of proteins needed to form healthy muscle.

There are many kinds of muscular dystrophy. Symptoms of the most common variety begin in childhood, mostly in boys. Other types don't surface until adulthood.

There's no cure for muscular dystrophy. But medications and therapy can help manage symptoms and slow the course of the disease.

Symptoms

The main sign of muscular dystrophy is progressive muscle weakness. Specific signs and symptoms begin at different ages and in different muscle groups, depending on the type of muscular dystrophy.

Duchenne type muscular dystrophy

This is the most common form. Although girls can be carriers and mildly affected, it's much more common in boys.

Signs and symptoms, which typically appear in early childhood, might include:

• Frequent falls
• Difficulty rising from a lying or sitting position
• Trouble running and jumping
• Waddling gait
• Walking on the toes
• Large calf muscles
• Muscle pain and stiffness
• Learning disabilities
• Delayed growth

Becker muscular dystrophy

Signs and symptoms are similar to those of Duchenne muscular dystrophy, but tend to be milder and progress more slowly. Symptoms generally begin in the teens but might not occur until the mid-20s or later.

Other types of muscular dystrophy

Some types of muscular dystrophy are defined by a specific feature or by where in the body symptoms begin. Examples include:

• Myotonic. This is characterized by an inability to relax muscles following contractions. Facial and neck muscles are usually the first to be affected. People with this form typically have long, thin faces; drooping eyelids; and swanlike necks.
• Facioscapulohumeral (FSHD). Muscle weakness typically begins in the face, hip and shoulders. The shoulder blades might stick out like wings when arms are raised. Onset usually occurs in the teenage years but can begin in childhood or as late as age 50.
• Congenital. This type affects boys and girls and is apparent at birth or before age 2. Some forms progress slowly and cause only mild disability, while others progress rapidly and cause severe impairment.
• Limb-girdle. Hip and shoulder muscles are usually affected first. People with this type of muscular dystrophy might have difficulty lifting the front part of the foot and so might trip frequently. Onset usually begins in childhood or the teenage years.

When to see a doctor

Seek medical advice if you notice signs of muscle weakness — such as increased clumsiness and falling — in you or your child.

Causes

Certain genes are involved in making proteins that protect muscle fibers. Muscular dystrophy occurs when one of these genes is defective.

Each form of muscular dystrophy is caused by a genetic mutation particular to that type of the disease. Most of these mutations are inherited.

Risk factors

Muscular dystrophy occurs in both sexes and in all ages and races. However, the most common variety, Duchenne, usually occurs in young boys. People with a family history of muscular dystrophy are at higher risk of developing the disease or passing it on to their children.

Complications

The complications of progressive muscle weakness include:

• Trouble walking. Some people with muscular dystrophy eventually need to use a wheelchair.
• Trouble using arms. Daily activities can become more difficult if the muscles of the arms and shoulders are affected.
• Shortening of muscles or tendons around joints (contractures). Contractures can further limit mobility.
• Breathing problems. Progressive weakness can affect the muscles associated with breathing. People with muscular dystrophy might eventually need to use a breathing assistance device (ventilator), initially at night but possibly also during the day.
• Curved spine (scoliosis). Weakened muscles might be unable to hold the spine straight.
• Heart problems. Muscular dystrophy can reduce the efficiency of the heart muscle.
• Swallowing problems. If the muscles involved with swallowing are affected, nutritional problems and aspiration pneumonia can develop. Feeding tubes might be an option.

Diagnosis

Your doctor is likely to start with a medical history and physical examination.

After that, your doctor might recommend:

• Enzyme tests. Damaged muscles release enzymes, such as creatine kinase (CK), into your blood. In a person who hasn't had a traumatic injury, high blood levels of creatine kinase (CK) suggest a muscle disease.
• Genetic testing. Blood samples can be examined for mutations in some of the genes that cause types of muscular dystrophy.
• Muscle biopsy. A small piece of muscle can be removed through an incision or with a hollow needle. Analysis of the tissue sample can distinguish muscular dystrophies from other muscle diseases.
• Heart-monitoring tests (electrocardiography and echocardiogram). These tests are used to check heart function, especially in people diagnosed with myotonic muscular dystrophy.
• Lung-monitoring tests. These tests are used to check lung function.
• Electromyography. An electrode needle is inserted into the muscle to be tested. Electrical activity is measured as you relax and as you gently tighten the muscle. Changes in the pattern of electrical activity can confirm a muscle disease.

Treatment

Although there's no cure for any form of muscular dystrophy, treatment for some forms of the disease can help extend the time a person with the disease can remain mobile and help with heart and lung muscle strength. Trials of new therapies are ongoing.

People with muscular dystrophy should be monitored throughout their lives. Their care team should include a neurologist with expertise in neuromuscular diseases, a physical medicine and rehabilitation specialist, and physical and occupational therapists.

Some people might also need a lung specialist (pulmonologist), a heart specialist (cardiologist, a sleep specialist, a specialist in the endocrine system (endocrinologist), an orthopedic surgeon and other specialists.

Treatment options include medications, physical and occupational therapy, and surgical and other procedures. Ongoing assessments of walking, swallowing, breathing and hand function enable the treatment team to adjust treatments as the disease progresses.

Medications

Your doctor might recommend:

• Corticosteroids, such as prednisone and deflazacort (Emflaza), which can help muscle strength and delay the progression of certain types of muscular dystrophy. But prolonged use of these types of drugs can cause weight gain and weakened bones, increasing fracture risk.

• Newer drugs include eteplirsen (Exondys 51), the first medication to be approved by the Food and Drug Administration (FDA) specifically to treat some people with Duchenne muscular dystrophy. It was conditionally approved in 2016.

  In 2019, the Food and Drug Administration (FDA) approved golodirsen (Vyondys 53) for treatment of some people with Duchenne dystrophy who have a certain genetic mutation.

• Heart medications, such as angiotensin-converting enzyme (ACE) inhibitors or beta blockers, if muscular dystrophy damages the heart.

Therapy

Several types of therapy and assistive devices can improve the quality and sometimes the length of life in people who have muscular dystrophy. Examples include:

• Range-of-motion and stretching exercises. Muscular dystrophy can restrict the flexibility and mobility of joints. Limbs often draw inward and become fixed in that position. Range-of-motion exercises can help to keep joints as flexible as possible.
• Exercise. Low-impact aerobic exercise, such as walking and swimming, can help maintain strength, mobility and general health. Some types of strengthening exercises also might be helpful. But it's important to talk to your doctor first because some types of exercise might be harmful.
• Braces. Braces can help keep muscles and tendons stretched and flexible, slowing the progression of contractures. Braces can also aid mobility and function by providing support for weakened muscles.
• Mobility aids. Canes, walkers and wheelchairs can help maintain mobility and independence.
• Breathing assistance. As respiratory muscles weaken, a sleep apnea device might help improve oxygen delivery during the night. Some people with severe muscular dystrophy need to use a machine that forces air in and out of their lungs (ventilator).

Surgery

Surgery might be needed to correct contractures or a spinal curvature that could eventually make breathing more difficult. Heart function may be improved with a pacemaker or other cardiac device.

Preventing respiratory infections

Respiratory infections can become a problem in muscular dystrophy. So, it's important to be vaccinated for pneumonia and to keep up to date with influenza shots. Try to avoid contact with children or adults who have an obvious infection.

Coping and support

A diagnosis of muscular dystrophy can be extremely challenging. To help you cope, find someone to talk with. You might feel comfortable discussing your feelings with a friend or family member, or you might prefer meeting with a formal support group.

If your child has muscular dystrophy, ask your doctor about ways to discuss this progressive condition with your child.

Preparing for your appointment

You might be referred to a doctor who specializes in the diagnosis and treatment of muscular dystrophy.

What you can do

• Write down your or your child's signs and symptoms and when they began.
• Bring photos or video recordings to show the doctor the symptoms that concern you.
• Write down key medical information, including other conditions.
• Make a list of all medications, vitamins and supplements you or your child takes, including doses.
• Tell your doctor whether anyone in your family has been diagnosed with muscular dystrophy.

Questions to ask your or your child's doctor

• What's the most likely cause of these signs and symptoms?
• What tests are needed?
• What are the possible complications of this condition?
• What treatments do you recommend?
• What is the long-term outlook?
• Do you recommend that our family meet with a genetic counselor?

Don't hesitate to ask other questions during your appointment.

What to expect from your doctor

Your doctor is likely to ask you questions, such as:

• Are the symptoms getting worse?
• What, if anything, relieves them?
• What, if anything, makes them worse?
• Do you plan on having more children?