What Is Duchenne Muscular Dystrophy?
Muscular dystrophies are a group of diseases that make muscles weaker and less flexible over time. Duchenne muscular dystrophy (DMD) is the most common type. It’s caused by flaws in the gene that controls how the body keeps muscles healthy.
The disease almost always affects boys, and symptoms usually begin early in childhood. Children with DMD have a hard time standing up, walking, and climbing stairs. Many eventually need wheelchairs to get around. They can also have heart and lung problems.
Although there isn't a cure, the outlook for people with DMD is better than it has ever been. Years ago, children with the disease usually didn’t live beyond their teens. Today, they live well into their 30s, and sometimes into their 40s and 50s. There are therapies that can ease symptoms, and researchers are looking for new ones, as well.
DMD is caused by a problem in one of your genes. Genes contain the information your body needs to make proteins, which carry out many different body functions.
If you have DMD, the gene that makes a protein called dystrophin is broken. This protein normally keeps muscles strong and protects them from injury.
The condition is more common in boys because of the way parents pass DMD genes to their children. It’s what scientists call a sex-linked disease because it’s connected to the groups of genes, called chromosomes, that determine if a baby is a boy or a girl.
It’s rare, but sometimes people who don't have a family history of DMD get the disease when their genes get defects on their own.
If your child has DMD, you’ll probably notice the first signs before they turn 6 years old. Muscles in the legs are usually some of the first affected, so they’ll probably start to walk much later than other children their age. Once they can walk, they may fall down often and have trouble climbing stairs or getting up from the floor. After a few years, they might also begin to waddle or walk on their toes.
DMD also can damage the heart, lungs, and other parts of the body. As they get older, your child might have other symptoms, including:
- A curved spine, also called scoliosis
- Shortened, tight muscles in their legs, called contractures
- Problems with learning and memory
- Shortness of breath
- Trouble concentrating
The muscle problems can cause cramps at times, but in general, DMD isn’t painful. Your child will still have control of their bladder and bowels. Although some children with the disorder have learning and behavior problems, DMD doesn’t affect your child’s intelligence.
Getting a Diagnosis
You should let your child’s doctor know about the symptoms you’ve been noticing. They’ll want to know your child’s medical history, then ask questions about their symptoms, like:
- 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 give your child a physical exam, and they may do some tests to rule out other conditions that can cause muscle weakness.
If the doctor suspects DMD, they’ll do some other tests, including:
- Blood tests. The doctor will take a sample of your child’s blood and test it for creatine kinase, an enzyme that your muscles release when they are damaged. A high CK level is a sign that your child could have DMD.
- Gene tests. Doctors can also test the blood sample to look for a change in the dystrophin gene that causes DMD. Girls in the family can get the test to see if they carry this gene.
- Muscle biopsy. Using a needle, the doctor removes a tiny piece of your child’s muscle. They’ll look at it under a microscope to check for low levels of dystrophin, the protein that is missing in people with DMD.
Questions for Your Doctor
If your child has DMD, you’ll want to get as much information about their condition as you can. Think about 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 them feel?
- How can I help them be active?
- What kind of diet should they eat?
There’s no cure for DMD, but there are medicines and other therapies that can ease your child’s symptoms, protect their muscles, and keep their heart and lungs healthy.
Eteplirsen (Exondys 51) has been approved to treat individuals with a specific mutation of the gene that leads to DMD. It is an injection medication. Its most common side effects are balance problems and vomiting. Although the drug increases dystrophin production, which would predict improvement in muscle function, this has not yet been shown.
The oral corticosteroid deflazacort (Emflaza) was approved in 2017 to treat DMD, becoming the first FDA approval of any corticosteroid to treat the condition. Deflazacort has been found to help patients retain muscle strength as well as helping them maintain their ability to walk. Common side effects include puffiness, increased appetite and weight gain.
Steroids such as prednisone slow muscle damage. Children who take this medicine are able to walk for 2 to 5 years longer than they would without it. The drugs also can help your child’s heart and lungs work better.
Because DMD can cause heart problems, it's important for your child to see a heart doctor, called a cardiologist, for checkups once every 2 years until age 10, and once a year after that. Girls and women who carry the gene have a higher risk of heart problems, too. They should see a cardiologist in their late teens or early adult years to check for any problems.
For the small number of DMD patients with the gene mutation exon 45 skipping, the injectable casimersen (Amondys 45) has been appropved. It is the first targeted treatment for this type of mutation and has been shown to help increase the production of dystophin.
A small number of children with DMD may also have a gene mutation that is amenable to exon 53 Skipping. The drug golodirsen (Vyondys 53) has been approved to help increase the amount of dystophin in the muscle fibers.
Some blood pressure medicines may help protect against muscle damage in the heart.
Kids with DMD might need surgery to fix shortened muscles, straighten the spine, or treat a heart or lung problem.
Scientists continue to look for new ways to treat DMD in clinical trials. These trials test new drugs to see if they are safe and if they work. They often are a way for people to try new medicine that isn't available to everyone. Your doctor can tell you if one of these trials might be a good fit for your child.
Taking Care of Your Child
It’s overwhelming to learn that your child has DMD. Remember that the disease doesn’t mean they can’t go to school, play sports, and have fun with friends. If you stick with their treatment plan and know what works for your child, you can help them live an active life.
- Stand and walk as much as possible. Being upright will keep your child’s bones strong and their spine straight. Braces or standing walkers can make it easier for them to stand and get around.
- Eat right. There's no special diet for children with DMD, but healthy foods can prevent weight problems or help with constipation. Work with a dietitian to make sure your child eats the right balance of nutrients and calories each day. You may need to see a specialist if your child has trouble swallowing.
- Stay active. Exercise and stretches can keep your child’s muscles and joints limber and help them feel better. A physical therapist can teach them how to exercise safely without overworking.
- Find support. Other families living with DMD can be great resources for advice and understanding about life with the disease. Find a local support group or explore online discussion boards. It may also help you to talk about your feelings with a psychologist or counselor.
What to Expect
As your child gets older, their muscles will become weaker and they most likely won’t be able to walk. Many boys with DMD will need a wheelchair by the time they are 12 years old to help them get around. Although some kids live only into their teens, the outlook for this condition is much better than it used to be. Today, young adults with DMD can go to college, have careers, marry, and start families.
Scientists are also testing new ways to treat the genes that cause DMD. These treatments might soon improve the outlook for even more for people with DMD. In 2019, the FDA approved golodirsen injection (Vyondys 53,) as the first treatment for DMD in patients with a confirmed mutation amenable to exon 53 skipping and in 2014, officials in Europe approved ataluren (Translarna) as the first drug to treat the genetic cause of DMD. A few other gene therapies may soon be ready for sale in the U.S.