Duchenne muscular dystrophy (DMD) follows an X-linked inheritance pattern. The condition most often affects males, while females may be carriers of the genetic change that causes it.
If you have DMD, your body does not make enough of a protein called dystrophin. The lack of dystrophin in your body leads to reduced muscle function over time.
DMD is inherited, or passed from parents to children through genetics. People with DMD are born with a gene mutation (change) that interrupts or prevents the production of dystrophin.
Let’s take a closer look at how this inheritance generally occurs for people with DMD.
Chromosomes are structures in human cells. They
Females typically have two X chromosomes, while males typically have one X chromosome and one Y chromosome.
The gene for dystrophin production is passed down on the X chromosome. If you’re female, you have one copy of this gene on each chromosome. This means that if you inherited one copy with the DMD mutation, you usually have another copy that can act as a backup.
If you’re male, you have just one copy of the dystrophin gene, which means you don’t have a backup. This is why DMD is much more common in males. Females can experience some symptoms of DMD, but the symptoms are usually not as severe as those in males.
In some rare cases, someone who is female might have two copies of the gene that doesn’t make enough dystrophin. They might lack a second X chromosome, or the second X chromosome might have damage or differences that affect dystrophin production.
You can inherit the gene for DMD from your mother or your father. But that might not mean you have DMD — it may take one more generation for someone in your family to develop DMD.
If you’re male and have DMD, you’ll pass your one X chromosome to any female children you have, and they will become carriers of the gene. But if you have male children, they will inherit only the Y chromosome from you and will not inherit the DMD gene.
If you’re female and carry the DMD gene on one of your X chromosomes, you have a 50% chance of passing the gene to each of your children. Each child will inherit one of your two X chromosomes.
Because your male children will have only one copy of the X chromosome, they’ll have a 50% chance of inheriting DMD. Female children will have a 50% chance of becoming carriers of the gene.
A carrier is someone who has a mutation on the dystrophin-producing gene on an X chromosome. You can find out if you’re a carrier through genetic counseling and genetic testing.
A genetic counselor can identify people in your family who might be carriers. Genetic testing uses a sample of saliva or blood.
Multiple types of mutations on the dystrophin-producing gene can cause DMD. Knowing the type of mutation makes a difference when you choose a genetic test.
If you already know the mutation, the test will check for that specific mutation. If you don’t, you can do comprehensive genetic testing to find carriers in your family.
If you’re male and have DMD, you cannot pass your X chromosome to your male children, but you will pass it to your female children. It’s unlikely that your female children will have DMD, but your male grandchildren will have a 50% chance of developing DMD.
If you’re female and are a carrier of the DMD gene, your male children will have a 50% chance of having DMD, and your female children will have a 50% chance of becoming a carrier.
Although DMD is usually part of a known inheritance pattern in families, the condition can also occur spontaneously. This means a baby can be born with DMD even though there is no known history of DMD in the family.
This can happen when one of the mother’s egg cells has a new genetic mutation that she passes on to her child. Alternatively, a genetic mutation might have occurred in the egg or sperm before the mother was born, making her an unknowing carrier of the gene.
It’s also possible that the gene for DMD has been passed down for generations within a family but that no one has yet been affected or received a proper diagnosis.
Doctors diagnose DMD using a combination of tests, such as:
- Serum creatine kinase (CK): High levels of CK in the blood peak at about
2 years of age and decrease as DMD progresses. Carriers can also have high levels of CK, and levels typically peak between 8 and 12 years of age. - Muscle biopsy: Samples of specific leg muscles can show signs of changes due to DMD.
- Genetic testing: Genetic tests check for the absence of the dystrophin-producing gene.
Doctors might also order tests to check your heart function, such as an echocardiogram or electrocardiogram, or electromyography, which checks for changes in muscle and nerve function that DMD can cause.
Early testing can lead to a quicker diagnosis of DMD. This means treatment can start sooner to potentially slow the progression of the disease. Emerging treatments such as gene therapy may be most effective earlier in the course of DMD.
A 2023 study of treatment goals for people with DMD found that those goals often shifted as the condition progressed.
The researchers concluded that treatments should continue to focus on helping people keep up their daily functions and recreational activities and that, in the long term, treatments should be individualized to help people manage social and emotional challenges.
Another 2023 study, based on data from the years 2000 through 2015, showed that the time from early symptoms to DMD diagnosis was 2.2 years. This timing was unchanged from previous data from 1982 through 2000.
The genetic mutation for Duchenne muscular dystrophy (DMD) can be passed down by either parent. Usually, females who inherit the gene become carriers, while males develop DMD.
Early testing can help families get an earlier start on treatment to reach individual goals, such as maintaining daily functioning, recreation, and social and emotional health.