Duchenne muscular dystrophy (DMD) in children

Muscular dystrophies are a group of disorders that make muscles weaker and less flexible over time. Duchenne muscular dystrophy (DMD) is the most common type. It is caused by defects in a gene that controls how the body maintains healthy muscles.

The disease almost always affects boys, and symptoms usually appear in early childhood. Children with DMD have difficulty standing, walking, and climbing stairs. Many end up needing wheelchairs to get around. They may also have heart and lung problems.

Although there is no cure, the outlook for people with DMD is better than ever. A few years ago, children with this disease usually did not survive into adolescence. Today they live up to 30, and sometimes up to 40 and 50 years. There are treatments that can relieve symptoms, and researchers are also looking for new ones.

Causes

DMD is caused by a problem in one of your genes. Genes contain the information your body needs to make proteins that perform many different bodily functions.

If you have DMD, the gene that makes a protein called dystrophin is broken. This protein usually maintains muscle strength and protects it from injury.

The disease is more common in boys due to the fact that parents pass on the genes for DMD to their children. This is what scientists call a sex-linked disease because it is linked to groups of genes called chromosomes that determine whether a child will be a boy or a girl.

It's rare, but sometimes people who don't have a family history of DMD get sick when their genes themselves are defective.

Symptoms

If your child has DMD, you will most likely notice the first signs before age 6. The leg muscles are usually among the first to be affected, so they are likely to start walking much later than other children their age. Once they are able to walk, they may fall frequently and have difficulty climbing stairs or getting up off the ground. After a few years, they may also begin to waddle or walk on tiptoe.

DMD can also affect the heart, lungs, and other parts of the body. As your child gets older, other symptoms may appear, including:

A curved spine, also called scoliosis
Shortened, tight muscles in their legs, called contractures
Headaches
Problems with learning and memory
Shortness of breath
Sleepiness
Trouble concentrating

Muscle problems can sometimes cause cramps, but DMD is usually not painful. Your child will always have control of his bladder and bowels. Although some children with the condition have learning and behavioral problems, DMD does not affect your child's intelligence.

Geting a diagnosis

You should tell your child's doctor about any symptoms you notice. They will want to know your child's medical history and then ask about their symptoms, such as:

How old was your child when they started walking?
How well do they do things like run, climb stairs, or get up from the floor?
How long have you noticed these problems?
Does anyone else in your family have muscular dystrophy? If so, what kind?
Do they have any trouble breathing?
How well do they pay attention or remember things?

The doctor will perform a physical exam on your child and may run tests to rule out other conditions that may be causing muscle weakness.

If a doctor suspects DMD, they will do other tests, including:

Blood tests. The doctor will take a sample of your child's blood and test it for the presence of creatine kinase, an enzyme your muscles release when they are damaged. High levels of creatine kinase are a sign that your child may have DMD.
Genetic testing. Doctors may also test a blood sample to look for the change in the dystrophin gene that causes DMD. Daughters in the family may be tested to see if they carry the gene.
Muscle biopsy. Using a needle, the doctor takes a small piece of muscle from the child. They will examine it under a microscope to check for low levels of dystrophin, a protein that people with DMD lack.

Questions for the doctor

If your child has DMD, you need to get as much information as possible about their condition. Consider asking:

What does this mean for my child?
Do they need to see any other doctors?
What kind of treatments are there?
How will they make him feel?
How can I help him be active?
What kind of diet should they eat?

Treatment

There is no cure for DMD, but there are medications and other treatments that can relieve your child's symptoms, protect their muscles, and keep their heart and lungs healthy.

Eteplirsen (Exondys 51) is approved for the treatment of DMD. It is an injectable drug that helps treat people with a specific gene mutation that leads to Duchenne muscular dystrophy. The most common side effects are balance problems and vomiting. Although the drug increases dystrophin production, which may predict improvement in muscle function, this has yet to be demonstrated.

The oral corticosteroid deflazacort (Emflaza) was approved in 2017 for the treatment of DMD. Deflazacort has been found to help patients maintain muscle strength as well as the ability to walk. Common side effects include swelling, increased appetite, and weight gain.

Steroids such as prednisone slow down muscle damage. Children taking this drug can walk 2 to 5 years longer than without it. Medicines can also help your child's heart and lungs work better.

Because DMD can cause heart problems, it's important that your child sees a cardiologist for a checkup every 2 years up to age 10 and once a year thereafter. Girls and women who carry this gene also have a higher risk of heart problems. They should see a cardiologist in their teens or early adulthood to check for any problems.

A small number of children with DMD dystrophy may also have a genetic mutation that results in exon 53 skipping. The drug holodirsen (Vyondys 53) is approved to increase the amount of dystophine in muscle fibers.

Some blood pressure medications can help protect against damage to the heart muscle.

Children with DMD may need surgery to repair shortened muscles, straighten the spine, or treat heart or lung problems.

Scientists continue to look for new ways to treat DMD in clinical trials. These trials test new drugs to make sure they are safe and work. They are often a way to try new drugs that are not available to everyone. Your doctor can tell you if any of these tests are right for your child.

Caring for your child

It is very difficult to know that your child has DMD. Remember that being sick doesn't mean they can't go to school, play sports, and have fun with friends. If you stick to their treatment plan and know what works for your child, you can help them stay active.

Get up and walk as much as you can. In a standing position, your child's bones will be strong and the spine will be straight. Braces or a walker can make it easier for him to stand and walk.
Eat well. There is no special diet for children with DMD, but eating healthy can prevent weight problems or help with constipation. Work with a registered dietitian to make sure your child is eating the right balance of nutrients and calories every day. You may need to see a specialist if your child has trouble swallowing.
Stay active. Exercise and stretching can keep your child's muscles and joints flexible and help them feel better. A physical therapist can teach him how to exercise safely without overworking himself.
Find support. Other families living with DMD can be great sources of advice and insight on how to live with the disease. Find a local support group or explore online discussion forums. It can also help you talk about your feelings with a psychologist or counselor.

What to expect

As your child gets older, his muscles weaken and he probably won't be able to walk. Many boys with DMD will need a wheelchair by age 12 to get around. While some children only survive into adolescence, the outlook for this disease is much better than it used to be. Today, young people with DMD can go to college, pursue careers, marry, and start families.