Genetic Testing for Duchenne Muscular Dystrophy

This article was updated in June 2025 by Andrea Enguita Marruedo, PhD (Medical Content Writer at myTomorrows) to include new insights and reflect the progress made in genetic testing for Duchenne Muscular Dystrophy since it was first published in 2022.

This blog is designed to provide information about the genetic causes of Duchenne Muscular Dystrophy (DMD) and the role of genetic testing in diagnosing the condition. It covers the different genetic mutations that can lead to Duchenne Muscular Dystrophy, how the condition is inherited, what genetic testing is, and the types of tests available—including options during pregnancy. It is intended for those living with Duchenne Muscular Dystrophy, their families, caregivers, and anyone seeking to understand how genetic testing works and how it can support early diagnosis and treatment planning.

What is Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a genetic condition caused by different mutations (changes in the DNA) within the dystrophin gene, which is located on the X chromosome. This gene is responsible for producing the dystrophin protein, which plays an important role in keeping muscle cells intact. It acts like a shock absorber in muscle cells, helping to protect muscle fibers from getting damaged during contractions. Without enough dystrophin, muscles gradually become damaged and weaker.^​​1

Duchenne Muscular Dystrophy mostly affects males, but in rare cases, females can be affected too. In Europe and North America, about 6 in every 100,000 people are living with the condition.¹

Looking for more information about what causes Duchenne, how it’s diagnosed, and the signs to look for? Read our blog ‘Living with Duchenne Muscular Dystrophy: Treatments and Care Essentials’.

What types of dystrophin gene mutations cause Duchenne?

Duchenne Muscular Dystrophy can result from different mutations within the dystrophin gene, which is made up of 79 sections called exons. Having so many exons makes it one of the largest genes in the human body. Due to its large size, a wide range of mutations can occur along different parts of the gene. The most common types of dystrophin gene mutations that cause Duchenne include:

• Deletions (60-70% of the cases): In this type of mutation, one or more exons are missing. ^{2, 3, 4}
• Large duplications (10% of the cases): This occurs when one or more exons within the gene are duplicated, leading to extra copies of those segments. ^{2, 3, 4}
• Point mutations (20-30% of the cases): These are smaller changes in the gene that do not involve an entire gene section or exon. The most common form is a ‘nonsense variant’, which creates a “stop signal”, prematurely ending the production of dystrophin.^{2, 3, 4}

Depending on the specific mutation and how it affects dystrophin production, some of these changes can lead to a milder condition called Becker Muscular Dystrophy (BMD) instead of Duchenne. In Becker Muscular Dystrophy, the body still produces some dystrophin— just in a shorter, less effective form — so muscle weakening happens more slowly and is generally less severe.

If you want to know more about Becker Muscular Dystrophy, visit our blog ‘Navigating Becker Muscular Dystrophy: Symptoms, Diagnosis, and Treatment Options’.

Why does Duchenne Muscular Dystrophy mainly affect males?

Duchenne Muscular Dystrophy mostly affects males because the dystrophin gene is located on the X chromosome —one of the chromosomes that determines a person’s biological sex.

Humans have 23 pairs of chromosomes (46 in total), with one set inherited from each parent. These chromosomes carry genes, which means most genes come in pairs—one copy from each parent. ^{5, 6, 7} However, sex chromosomes are an exception:

• Females have two X chromosomes (XX)
• Males have one X and one Y chromosome (XY)

Because males have only one X chromosome, they have only one copy of the genes located on it — such as the dystrophin gene — while females have two copies. ^{5, 7}

Males will develop Duchenne Muscular Dystrophy if their X chromosome carries the mutation, as they lack a second X chromosome to compensate. Females have two X chromosomes, so if only one carries the mutation, the other usually provides enough dystrophin to prevent the disease. However, they can still pass the mutation on to their children (as “carriers”).^{1, 5, 8} Only around 10%-20% of female carriers of Duchenne Muscular Dystrophy exhibit symptoms of the disease, and these are typically milder than those observed in males, with a few exceptions.^{8, 9, 10}

How do people get Duchenne Muscular Dystrophy?

Duchenne Muscular Dystrophy is commonly inherited (passed down from a parent) (passed down from a parent). However, about one-third of cases result from spontaneous mutations in the dystrophin gene, meaning there is no family history of the condition. ^{11, 12, 13}

Inherited

In most cases, Duchenne Muscular Dystrophy is passed down from a mother who is a carrier of the condition. This means she has one X chromosome with a mutation in the dystrophin gene, and one X chromosome without this mutation. Each of her children has a 50/50 chance of inheriting either X.

If the father is unaffected and the mother is a carrier of Duchenne Muscular Dystrophy:

• Each son has a 50% chance of inheriting the mutation and developing Duchenne Muscular Dystrophy ^{1, 8, 14}
• Each daughter has a 50% chance of inheriting the mutation and becoming a carrier. ^{1, 8, 14}

While this is highly unlikely due to the condition’s impact on mobility and life expectancy, in very rare cases a man with Duchenne may become a father. If the father is affected and the mother is unaffected and not a carrier:

• All daughters will get his X chromosome with the mutation and become carriers. ^{1, 8, 14}
• All sons will get his Y chromosome, so they won’t inherit Duchenne. ^{1, 8, 14}

If the father is affected and the mother is a carrier:

• All daughters will inherit the X chromosome with the mutation from their father. Each daughter then has a 50% chance of inheriting the affected X chromosome from the mother and developing Duchenne, or a 50% chance of inheriting the unaffected X and becoming a carrier.
• Each son will inherit the Y chromosome from the father (which does not carry the mutation). Sons have a 50% chance of inheriting the affected X chromosome from the mother and developing Duchenne, or a 50% chance of inheriting the unaffected X chromosome and not developing Duchenne.

Spontaneous cases (no family history)

These mutations happen randomly on the dystrophin gene, often very early after the egg is fertilized—before the baby even begins to develop. Because of this, the mutation ends up in every cell of the child’s body. ^{15, 16} Even though there’s no family history, once a child has this new mutation, it can be passed on to future generations. ^{1, 8, 14}

What is genetic testing for Duchenne Muscular Dystrophy?

Genetic testing, also known as DNA testing, is a type of medical test that looks for mutations in a person’s DNA.[17], [18] For Duchenne Muscular Dystrophy, genetic testing examines the dystrophin gene to detect the presence of a mutation and determine its specific type and location.¹, ^{19, 20} It is usually performed on a blood or saliva sample and is currently the most accurate and widely accepted way to diagnose Duchenne. ^{1, 21}

Genetic testing for Duchenne Muscular Dystrophy can:

• Confirm a Duchenne diagnosis and help rule out other similar conditions, such as Becker Muscular Dystrophy, which involves a different kind of mutation in the same gene. ^{19, 20}
• Help predict how the disease might progress, depending on the type and location of the mutation. ^{19, 20}
• Guide treatment decisions, especially since many current and upcoming therapies are “mutation-specific”, meaning they only work for people with certain types of mutations. Knowing the exact mutation is also necessary to access certain treatments or to join clinical trials for therapies that target specific mutations. ^{19, 20}
• Support wider testing within families. Once a mutation is identified in one family member, others can be tested to see if they carry the same genetic change. Genetic testing for Duchenne Muscular Dystrophy provides the most accurate way to identify carriers. ¹⁹

Types of Duchenne genetic tests

There are several types of DNA genetic tests used to diagnose Duchenne Muscular Dystrophy. The type of test a doctor recommends often depends on whether a specific mutation in the dystrophin gene has already been identified in the family.

If a known mutation exists in the family

When a specific mutation has already been identified in a family member, the doctor may request familial mutation testing. This test looks only for that exact mutation, making it faster and easier than testing the entire gene. The exact testing method used depends on the type of mutation that was previously found in other members of the family. ¹⁹

If the mutation has not yet been identified

In cases where no mutation has yet been identified, a step-by-step approach is usually followed:

1. Testing for large deletions and duplications: These tests are typically performed first as these types of mutations are the most common in Duchenne Muscular Dystrophy. The most common methods include multiplex ligation-dependent probe amplification (MLPA) and genomic hybridization (CGH array testing).^{19, 22, 23}
2. Testing for small mutations: If no deletions or duplications are found, the doctor may request to perform a technique called Sanger gene sequencing, which looks for smaller changes and point mutations in the gene. ¹⁹

A newer technology, called Next Generation sequencing, can detect deletions, duplications, and smaller point mutations in one single test. ^{19, 22, 23} While currently not yet available everywhere, it is increasingly being offered in specialized laboratories with access to advanced sequencing technology. ¹⁹

In a small number of cases (about 1–5%), no mutation is found even after thorough genetic testing with MLPA, CGH array testing, Sanger sequencing, or Next Generation Sequencing. ^{19, 24} This doesn’t always rule out Duchenne, and further testing may be needed to confirm the diagnosis. Follow-up tests may include:

• Muscle biopsy: A small sample of muscle tissue may be taken to directly measure the amount of dystrophin protein present in the muscle. In general, no dystrophin typically suggests Duchenne Muscular Dystrophy, while reduced levels of dystrophin often suggest Becker Muscular Dystrophy. ¹⁹
• RNA testing: These tests examine how well the instructions in the dystrophin gene are being “read” by the body to produce dystrophin protein. Normally, before the protein is made, the body first copies the gene into a molecule called messenger RNA. This messenger RNA carries the instructions to the part of the cell where proteins are built, so dystrophin can be produced. If earlier genetic tests do not find a mutation, this test can help show whether there’s a problem in this step of the process. In other words, while DNA testing looks at the genetic blueprint, RNA testing looks at whether that blueprint is being used correctly. ^{19, 24}

Can Duchenne be diagnosed during pregnancy?

For families with a history of Duchenne, prenatal genetic testing can assess whether a fetus carries the dystrophin gene mutation that causes the condition. ^{21, 25} Two main procedures are currently used to diagnose Duchenne during pregnancy:

• Chorionic villus sampling (CVS): This procedure is usually performed after 11 weeks of pregnancy. It involves collecting a small sample of tissue from the placenta, which contains fetal cells (cells from the developing baby). These cells are then tested for the specific Duchenne mutation present in the family.
• Amniocentesis: This test is typically carried out after 15–16 weeks of pregnancy. It involves collecting a sample of amniotic fluid—the protective fluid surrounding the fetus. This fluid also contains fetal cells that can be analyzed for the Duchenne gene mutation. ^{21, 25}

Both procedures are generally considered safe but carry a small risk of miscarriage (the unintentional loss of a pregnancy), estimated to be between 0.25% and 1%. ^{25, 26, 27}

Non-invasive prenatal diagnosis

A newer approach called non-invasive prenatal diagnosis (NIPD) is currently being developed for genetic conditions like Duchenne Muscular Dystrophy. This method involves collecting a simple blood sample from the mother, which contains small DNA fragments of the fetus that naturally circulate in her bloodstream. These fragments can be analyzed to detect a specific Duchenne gene mutation. [21], [26], [29] Because NIPD does not require a sample from the uterus, it avoids the small risk of miscarriage associated with invasive procedures like chorionic villus sampling (CVS) or amniocentesis. Early research suggests that NIPD has a high level of accuracy when the specific familial mutation is known. However, NIPD is not currently considered an emerging technology for Duchenne diagnosis. It is not yet part of standard prenatal screening, and further research is ongoing to better understand its accuracy, availability, and potential for wider clinical use. ^{21,26, 28}

Limitations of Prenatal Genetic Testing

Prenatal genetic testing can have certain limitations. In some cases, results may be inconclusive, misleading, or unexpected. A normal result does not guarantee the baby will be free from all health conditions—it only confirms the absence of the specific muscular dystrophy mutation identified within the family. Furthermore, prenatal diagnosis can only be performed if there is a confirmed and clearly defined genetic diagnosis within the family. ^{21, 29}

Conclusions

Duchenne Muscular Dystrophy (DMD) is a genetic condition caused by mutations in the dystrophin gene. Genetic testing helps confirm a Duchenne diagnosis, identify the type of dystrophin mutation causing the condition and guide treatment decisions. There are several types of genetic tests. If a known Duchenne mutation runs in the family, familial mutation testing can check for that exact genetic change. If no mutation has been identified yet, testing usually follows a step-by-step process: first looking for large deletions or duplications, then checking for smaller mutations. A newer test called Next Generation Sequencing (NGS) can detect all these mutation types in a single test, although it is available only in a few specialized laboratories. In some cases, if no mutation is found, additional tests—such as a muscle biopsy or RNA analysis—may be needed. For families with a known Duchenne mutation, prenatal testing during pregnancy (via chorionic villus sampling or amniocentesis) can check whether the baby has inherited a specific Duchenne mutation. A newer, non-invasive method called non-invasive prenatal diagnosis (NIPD), which uses a blood sample from the mother, is also being developed for conditions like Duchenne.

At myTomorrows, we have a team of Patient Navigators, who are multi-lingual professionals with a medical background, who can help you to explore your treatment options and support you through your journey.

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