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

Duchenne muscular dystrophy is the most common form of muscular dystrophy. It’s caused by a gene mutation that affects how a person’s heart and skeletal muscles work. According to Cleveland Clinic, the mutation is often hereditary, passed down from mother to child. Someone with a family history of DMD has a higher risk of developing it. 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 tells your body how to produce a protein called dystrophin, which helps hold muscle fibers in place. It also allows your muscles — including your heart muscle — 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 — erasure of part of the dystrophin — although there are some other types of changes.

In people with DMD, the muscle cells can’t make enough normal dystrophin protein. When the child moves 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. Progressive muscle weakness is one of the main symptoms of DMD, especially if you notice it in your child’s legs and pelvis.

How 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 your children.

The Cleveland Clinic reports that about 2 out of 3 cases of DMD are caused by a mutation inherited from the mother’s genes. Prenatal testing can sometimes lead to a diagnosis of DMD early in the pregnancy. However, 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, it’s not your fault. You didn’t do anything to cause the gene change, and there’s no way to prevent it from occurring or being passed down.

Prenatal testing can sometimes lead to a diagnosis of DMD early in a pregnancy.

Duchenne.com, a medical resource for doctors and families affected by DMD, notes that about 1 out of 3 cases of DMD is caused by mutations that develop randomly in the mother’s egg cell. Called de novo germline mutations, they occur in a reproductive cell (egg or sperm) before conception and are passed to the offspring, affecting all of the child’s cells. A person won’t pass acquired mutations down to their children.

Your doctor can help you understand whether your child’s DMD was caused by an inherited or acquired 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. Here are six important facts about genetic testing for DMD.

1. Genetic Testing Helps Diagnose DMD

Genetic testing is the best way to diagnose DMD. A genetic diagnosis 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 and nerves are working properly.

Your child’s health care provider may recommend genetic testing if your child shows initial symptoms of DMD, such as:

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

Genetic testing is the best way to diagnose DMD.

Genetic testing may also help tell the difference between DMD and BMD. 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

According to the journal Sleep Science, severe DMD very rarely develops in females. It also affects males and females differently. This is because the gene is X-linked and recessive. But what does this mean and how is DMD passed from parents to offspring?

Chromosomes are the long pieces of DNA that contain our genes. Most humans have two sex chromosomes. According to Pfizer, males generally get an X chromosome from their mother and a Y chromosome from their father, whereas females generally get two X chromosomes, one from each parent.

The dystrophin gene is found on the X chromosome. Cedars-Sinai notes that because males usually only have one X chromosome, they typically have just one copy of the dystrophin gene. If it contains mutations, they will develop DMD.

Muscular Dystrophy Association (MDA) has found that 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. 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, per MDA.

MDA recommends that if you are a female who has a family member with DMD, it may help to undergo genetic testing to see if you have abnormalities in the DMD gene. This can tell you whether you’re at risk for cardiomyopathy (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 DMD treatments may help, depending on the cause of your child’s condition.

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

Dystrophin gene tests can tell you whether your child has DMD, but they can’t estimate your child’s prognosis (outlook) or determine how quickly their DMD 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 same gene change.

Because DMD is a neuromuscular disease, if genetic testing identifies abnormalities in the DMD gene, your child’s health care provider may refer you to a doctor specializing in neurology. An expert can help you better understand this rare genetic disorder and what to expect in your child’s future.

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 or deletion testing that can also help detect mutations.

One genetic test for DMD can detect 7 out of 10 possible gene mutations that cause DMD.

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 to see if it has 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 child’s genetic testing results. They can explain which mutations are 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 health care provider 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 a doctor or health practice that provides this service.

Free genetic testing for DMD and BMD 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? Do you have the DMD gene? Share your experiences in the comments below.