How Duchenne Muscular Dystrophy (DMD) Is Inherited

Duchenne muscular dystrophy (DMD) is a rare, incurable condition that typically begins in early childhood and is marked by worsening muscle weakness. The disease results from changes in a gene responsible for producing a vital muscle protein, dystrophin.

Duchenne muscular dystrophy is genetic, and people with a family history of the disease are at high risk of passing it on to their kids.

Read on to learn more about DMD inheritance and the role of genetic testing in diagnosing and treating the disease.

Duchenne muscular dystrophy almost always affects males. Understanding the genetic basis of the disease and the role of chromosomes (long strands of DNA containing hundreds to thousands of genes) helps explain DMD inheritance patterns.

DMD is said to be inherited in an X-linked recessive manner, meaning it is associated with a variant (also known as a mutation) in a gene on the X chromosome that tells the body how to make and use dystrophin.

The X chromosome is one of two so-called sex chromosomes; the other is Y. Males have an X and a Y chromosome while females have two X chromosomes. Children inherit one sex chromosome from each parent.

If a male inherits an X chromosome from either parent with a variant in the so-called Duchenne gene, he will be affected by DMD.

If a female inherits the variant on one of her X chromosomes with a normal gene on the other X chromosome, the X chromosome with the changed gene will undergo “inactivation” and she will not have DMD (or only mild symptoms). But she can be a carrier and pass the gene variant down to her children.

In about a quarter of cases, DMD occurs in people who have no family history of it. In these instances, the variant was not inherited but developed spontaneously in the mother’s egg cells.

Families may not know they have a history of DMD because the genetic variant may have existed for generations without being detected.

If a pregnant woman is a known carrier — or has a first- or second-degree relative who has the disease or is a known carrier — she may want to consider prenatal testing.

These testing methods include:

Noninvasive prenatal testing (NIPT), which analyzes small fragments of placental DNA floating in a pregnant woman’s blood to ascertain genetic variants in a fetus.
Chorionic villus sampling (CVS), in which a doctor removes chorionic villi cells from the placenta for analysis, usually 10 to 13 weeks into the pregnancy.
Amniocentesis, which is usually carried out 15 or 16 weeks into pregnancy. Amniocentesis involves inserting a needle into the uterus to extract a small amount of amniotic fluid, which contains cells shed by the fetus.

Children of parents who have DMD or are known carriers should also be tested, as should children with DMD symptoms. An early diagnosis can help ensure prompt access to treatment and counseling.

Testing can also help determine if a child has DMD or another type of muscular dystrophy. For instance, like DMD, Becker muscular dystrophy (BMD) is an X-linked recessive disorder involving the dystrophin gene, resulting in worsening muscle strength. Becker, however, is less common and less severe than DMD.

Usually, genetic testing of a parent or child requires just a simple blood or saliva sample. Genetic testing, however, may not be routine in some U.S. states.

Parent Project Muscular Dystrophy offers a program called Decode Duchenne that provides free genetic testing to eligible individuals. The application and testing process includes interpretation of results and counseling.

While not all newborns in the United States are screened for DMD, a few states have passed legislation to require it as part of a standard blood testing panel.

A number of possible gene variants can cause the body to make errors in its production of dystrophin. The makeup of the dystrophin gene consists of 79 coding regions called exons, numbered 1 to 79. DMD can occur when a part of one or more of those 79 pieces is missing (known as a gene deletion) or if there is an extra piece called a duplication.

In 2016 the U.S. Food and Drug Administration (FDA) approved the Exondys 51 (eteplirsen) injection, specifically indicated for patients who have a confirmed variant of the dystrophin gene responsible for exon 51 skipping, which affects about 13 percent of people with DMD. This type of therapy encourages the body’s cellular machinery to “skip over” an exon — in this case, exon 51 — thus enabling the production of an intact protein.

In 2023, the FDA approved Elevidys (delandistrogene moxeparvovec-rokl), a gene therapy for children ages 4 to 5 with Duchenne muscular dystrophy. Research has shown that in some patients Elevidys boosts dystrophin production to a level that is reasonably likely to provide real-life benefit.

Given through an intravenous dose, this therapy is designed to deliver a gene that leads to production of a micro-dystrophin, a shortened protein, which contains selected portions of the dystrophin protein present in normal muscle cells.

If a woman is a DMD carrier, she should consider consulting an obstetrician-gynecologist and a genetic counselor before becoming pregnant.

A genetic counselor can guide parents through the medical, psychological, and family implications of a genetic disease. Typically, a board-certified genetic counselor with master’s level training in genetic counseling, or a geneticist (a doctor who specializes in genetics) provides this type of counseling.

A professional can educate parents on the disorder and advise them on who else in their extended family may be impacted.

Genetic counselors can explain exactly what testing results mean, discuss possible follow-up testing, and go over specific therapies that are either approved or in clinical trials.

Scientific trials to find a cure and treatments for DMD are ongoing, and genetic counselors can alert parents who are interested in learning more about these options. (Find out more about scientific investigations looking for patients and carriers at PPMD’s Explore Clinical Trials.)

Genetic counselors are usually trained to provide psychological support as well, as having a child with DMD is emotionally challenging for families. They can also refer parents to longer-term psychological counseling and care.

While a child’s pediatrician or neurologist can provide a referral to a genetic counselor, DuchenneConnect allows participants to join a registry to access services such as genetic counseling and genetic testing, and resources to assist in the understanding and development of new treatment trials in Duchenne muscular dystrophy.

For adults or children who are carriers for DMD, signing up with the Duchenne Registry can help advance research by providing a better understanding of the impact of being a carrier and the significance of different types of genetic changes in DMD inheritance.

In most cases, Duchenne muscular dystrophy (DMD) is inherited; because of unique genetics, DMD inheritance almost always occurs in boys rather than girls.
Genetic testing of adults, children, and fetuses can detect DMD inheritance and help point the way to treatment and counseling.
Genetic therapies may improve strength and decrease debilitating symptoms.

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