• Duchenne muscular dystrophy (DMD) is caused by genetic changes that are often, but not always, passed from parent to child.
• Genetic testing is usually necessary to diagnose DMD.
• Genetic testing can help you understand whether certain treatments may be useful and provide information about whether family members also have DMD-causing genetic mutations.

Duchenne muscular dystrophy is caused by a gene mutation (change) that affects how a person’s muscles work. The mutation is often hereditary, passed down from parent to child. However, the mutation can also occur randomly, and many children with DMD don’t have family members with the condition.

Genetic testing is often part of the process of DMD diagnosis. These tests can determine whether a person has gene changes that could cause DMD for themselves, their children, or their grandchildren.

How Do Genes Cause DMD?

DMD is caused by mutations in the dystrophin gene. This gene instructs your body on how to produce a protein called dystrophin, which helps hold muscle cells in place. It also allows your muscles — including the muscles in your heart — to move properly without being damaged.

DMD develops when the dystrophin gene contains errors that prevent cells from making normal dystrophin protein. So far, researchers have found more than 2,000 mutations that lead to DMD and a related condition, Becker muscular dystrophy (BMD). These mutations often cause deletions — part of the dystrophin gene is erased — although some cause other types of changes.

In a child with DMD, their muscle cells can’t make enough normal dystrophin protein. When they move their muscles, their cells are left unprotected. The muscles then develop tears or can’t attach to the surrounding tissue as well as they should. Over time, the injured muscle cells die and are replaced with fat or scar tissue. This is why people with DMD lose muscle over time.

Is DMD Inherited?

DMD is often caused by gene mutations that are passed down within families. These changes — also called germline or inherited mutations — are present in all of a child’s cells at birth. If you have inherited mutations, you can also pass them down to any children you may have.

In about 2 out of 3 cases, DMD develops because of a mutation in the mother’s genes. In many cases, prospective mothers don’t know that they’re a carrier of this gene until they have a child with the condition. If you’re a carrier, know that you didn’t do anything to cause the gene change, and there’s no way to prevent it from occurring or being passed down.

About 1 out of 3 cases of DMD is caused by mutations that develop randomly in the mother’s egg cell or early on in the pregnancy. Called acquired or somatic mutations, they happen in a single cell and affect only that cell and any cells created by the original cell. A person won’t pass somatic mutations down to their children.

Your doctor can help you understand whether your child’s DMD was caused by an inherited or somatic mutation, and how this affects the risk of developing DMD for other family members.

What You Should Understand About Genetic Testing for DMD

Genetic testing looks for gene changes that may be causing DMD. These simple blood tests can have many benefits for you and your family.

1. Genetic Testing Helps Diagnose DMD

Genetic testing is the best way to diagnose DMD. It provides clear information about a child’s health and helps you understand which treatments may improve symptoms. Genetic testing is typically paired with other tests that can help your doctor understand whether your child’s muscles or nerves are working properly.

Your child’s doctor may recommend genetic testing if your child displays initial symptoms of DMD, such as:

• Muscle weakness that seems to be getting worse
• Muscle loss
• Difficulty walking or going up stairs
• Frequent falling
• Walking on the tips of their toes

Genetic testing can also help tell the difference between DMD and Becker muscular dystrophy. Mutations that disrupt the dystrophin gene more severely typically lead to DMD, while mutations that cause more minor changes often cause BMD. BMD causes similar symptoms to DMD, but the symptoms tend to be less severe and appear later on in childhood.

2. Genetic Testing May Be Useful for Females

DMD very rarely develops in females. This is because the gene is X-linked — and it affects males and females differently.

Chromosomes are the long pieces of DNA that contain our genes. Humans have two sex chromosomes. Males generally have an X chromosome and a Y chromosome, whereas females usually have two X chromosomes. The dystrophin gene is found on the X chromosome. This means that males typically have only one copy of the dystrophin gene. When it contains mutations, they will develop DMD.

When a female has an abnormal dystrophin gene on one X chromosome, they generally have a normal gene on the other X chromosome. This means that their cells will likely still make enough dystrophin protein and they won’t develop DMD. In rare cases, however, a female with a mutation may experience muscle or heart symptoms.

Mothers with one abnormal copy of the dystrophin gene are known as carriers. They have a 50 percent chance of passing the mutation on to their children.

If you are a female who has a family member with DMD, it may help to undergo genetic testing. This can inform you about whether you are at risk for experiencing heart problems or having a child with DMD.

3. Genetic Testing May Help Your Doctor Recommend Treatments

Some DMD treatments are specifically designed to help people who have certain mutations. Based on the results of genetic testing, you or your child may be able to use specific gene therapy or be eligible for a certain clinical trial.

Ask your doctor for more information about which types of treatments may help, depending on the cause of your child’s DMD.

4. Genetic Testing Won’t Help You Understand Disease Severity

Gene tests tell you whether your child has DMD, but they can’t estimate your child’s prognosis (outlook) or determine how quickly the condition will progress. DMD tends to look different for everyone — it may lead to slightly different symptoms or cause symptoms to worsen at different rates, even between two people with the exact same gene change.

5. Multiple Genetic Tests May Be Needed

Often, genetic testing for DMD involves a test called multiplex ligation-dependent probe amplification (MLPA). It can detect 7 out of 10 possible mutations that cause DMD. If MLPA doesn’t find any mutations but DMD seems likely, your doctor may recommend other tests such as gene sequencing that can also help detect mutations.

In the rare case that a sequencing test can’t detect a mutation, your doctor may suggest a muscle biopsy. For a muscle biopsy, doctors take a sample of muscle tissue and then a laboratory checks it for the presence of dystrophin protein. However, most people don’t need to undergo muscle biopsies.

6. Genetic Counseling Can Help You Learn More

When it comes to figuring out what genetic testing results mean, you’re not on your own. Genetic testing is typically paired with genetic counseling.

During this process, you meet with a genetic counselor, who can help you understand your results. They can explain which mutations are present in your child’s cells and what effect this may have on their health.

Based on the results, a genetic counselor can also help you understand whether genetic testing may be beneficial for other people in your family. Knowing whether you have a gene mutation that causes DMD helps you be more informed about your health and the health of any potential future children.

How To Get Your Child Tested for Muscular Dystrophy

If your child’s doctor thinks that they may have DMD symptoms, they’ll likely recommend genetic testing. They can tell you where to go to have your child’s blood drawn for a test or refer you to another doctor or health practice that provides this service.

Free genetic testing for DMD and Becker muscular dystrophy can be accessed through Parent Project Muscular Dystrophy. This advocacy organization provides this service for families who live in the U.S. or Canada.

Find Your Team

On myDMDcenter, the site for people with Duchenne muscular dystrophy and their loved ones, people come together to gain a new understanding of DMD and share their stories with others who understand life with DMD.

Have you or a loved one undergone genetic testing for DMD? Share your experiences in the comments below.