The genetics of DMD: What it means for your family

Last updated March 3, 2025, by Lindsey Shapiro, PhD
Fact-checked by Patrícia Silva, PhD

Most cases of Duchenne muscular dystrophy (DMD) — a genetic condition characterized by progressive muscle weakness and wasting — result from a parent passing down a disease-causing mutation to a child, usually from mother to son. While girls rarely develop DMD, they can carry mutations that are passed down to their own children.

As an inherited disease, a DMD diagnosis for one person can impact many other family members. Knowing that you carry a DMD-causing mutation may affect your choices surrounding family planning and reproduction.

Understanding DMD genetics and when genetic testing is necessary will help you make the best choices for yourself and your family. While these decisions can be complex, there is support available: A genetic counselor can help you understand genetic testing results and their implications so that you can make the most informed decision possible.

The role of genetics in DMD

DMD is a genetic condition caused by mutations in the DMD gene, which lead to a complete or near complete lack of the dystrophin protein. Dystrophin is important for protecting muscle cells against damage, and its loss in DMD causes symptoms of progressive muscle weakness and wasting.

Thousands of different disease-causing mutations have been identified in the DMD gene. While each affects the genetic code in different ways, they all eventually result in having less functional dystrophin than what’s needed to keep muscle cells healthy.

DMD gene mutations that lead to essentially having no dystrophin are associated with DMD disease.

DMD affects about 1 in 3,500 male newborns worldwide. Because of how the disease is inherited — through the X chromosome — it rarely affects females. But girls can carry disease-causing mutations that are passed down to their future children.

How is DMD inherited

The DMD gene is located on the X chromosome, one of the two sex chromosomes. Males have one X chromosome they inherit from their mother and a Y chromosome from their father. Females, meanwhile, have two X chromosomes, one inherited from each biological parent.

DMD often runs in families with an X-linked recessive inheritance pattern, which explains why the disease is nearly always seen in males.

Males who inherit a DMD-causing mutation on their single X chromosome inherited from their mother will have the disease.
Both X chromosomes in a female need to have a disease-causing mutation to develop DMD. If a mutation is only present on one of the X chromosomes, the healthy version on the other chromosome will usually cancel out any potential effects.

This difference explains why it’s very uncommon for girls to develop DMD — that happens only if both parents pass down a disease-causing mutation.

Women who carry a disease-causing mutation on one copy of their DMD gene are known as carriers. Carriers do not have DMD and the vast majority don’t experience any serious health effects. They can, however, experience mild symptoms such as muscle weakness or cramping, and may be at an elevated risk of heart issues.

A carrier can also pass down the DMD-causing mutation to her biological children.

If a carrier has a son, there is a 50% chance the son will inherit the mutated X chromosome and have DMD.
Assuming the father does not have DMD, there is a 50% chance that a daughter born to a carrier will also be a carrier.

If a man with DMD has children with a woman who is not a carrier, the male children will not inherit DMD, because men only give a Y chromosome to their sons. There will, however, be a 50% chance that a daughter will be a carrier.

Should a man with DMD and a woman who is a carrier have children, there’s a 50% chance that a son will have the disease. Any daughter will be a carrier of DMD-causing mutations and each one would have a 50% chance of having DMD.

In some cases, a son may be born with DMD even when there’s no family history of the disease. This may be because the mutation has been unknowingly passed down in female family members for generations.

However, it is also possible for DMD mutations to occur spontaneously, a process called de novo mutations. De novo is a Latin phrase meaning anew, or from the beginning. This happens in about one-third of people with DMD.

How genetic testing works

Genetic testing is the definitive test for identifying whether a person has DMD or is a carrier. It involves analyzing a person’s DNA — usually from a small blood or saliva sample — to identify disease-causing mutations in the DMD gene.

There are different types of genetic testing, and your doctor will choose one based on your family’s specific situation. If there is a known mutation that runs in your family, your doctor will typically choose a test that looks for that specific mutation. Otherwise, the clinician will likely order tests that more broadly screen the DMD gene for any mutations.

There are several reasons why someone may consider genetic testing for DMD, including:

to confirm a diagnosis in a child who is showing possible signs of DMD by ruling out conditions that may have overlapping symptoms
to establish or rule out carrier status in girls and women who are at risk based on their family history
as part of prenatal testing to evaluate whether a developing fetus is positive for DMD or related disease-causing mutations.

In any case, families should always talk with a genetic counselor before having genetic testing. Genetic counselors are trained professionals who can explain DMD inheritance in addition to offering guidance about the process and the possible implications of the test results.

Family planning and reproductive options

A DMD diagnosis should be discussed with a genetic counselor, who can advise if anyone else should be tested and what it means for future reproductive decisions for anyone affected.

For a mother whose son has been diagnosed with DMD, genetic testing can show whether she is a carrier or if the son has a de novo mutation. If she tests positive as a carrier, she should discuss the option of genetic testing with her other children. Sons who are in their teens or older and are not showing signs of the disease may not need testing.

If a mother tests negative for being a carrier, there is a rare risk that she has germline mosaicism, which means some of her egg cells have a mutation but not the blood cells that were tested. In such cases, the woman’s children may still want to consider being tested.

Women who ultimately test positive as carriers will know that there is a 50% chance any son will have DMD and a 50% chance any daughter will be a carrier.

If you test positive as a DMD carrier, you have many reproductive options to consider, including:

natural pregnancy with the possibility that your child might have DMD
natural pregnancy with prenatal genetic testing
preimplantation genetic diagnosis, known as PGD
egg or sperm donation
adoption.

With PGD, parents will begin the process of in vitro fertilization, known as IVF, in which the mother’s egg is fertilized with the father’s sperm in the laboratory. The embryo is then implanted into the mother’s uterus. Before the implantation, cells from the embryo can be genetically tested for DMD mutations, and only embryos that test negative will be implanted.

Women who are carriers may also choose to use a donor egg so they don’t pass on the mutation to their children. Likewise, men with DMD can use donor sperm so that they don’t pass on a mutation to their daughters.

A newer technology called sperm sorting can differentiate between X chromosome-containing sperm and Y chromosome-containing sperm. The selection of X-containing sperm increases the chance of having a daughter and reduces the chances of a son who has DMD. This technology is not approved in the U.S., but is available in other countries.

When considering any reproductive options, it is important to talk with your healthcare providers and a genetic counselor. Your team will help you understand all of your options and guide you in making the best decision for yourself and your family. They’ll also be able to refer you to specialists, including experts in reproductive medicine.

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