Duchenne muscular dystrophy (DMD) inheritance: What to know
Duchenne muscular dystrophy (DMD) occurs as a result of genetic changes on the X chromosome. If someone has a gene change that can cause DMD, their children may inherit that change.
DMD is a progressive condition that causes muscle fibers to break down and weaken. People with DMD develop muscle weakness that can lead to life threatening complications such as cardiomyopathy (heart muscle disease) and breathing difficulties.
DMD results from changes in the DMD gene that stop a person’s body from making enough functional dystrophin. Dystrophin is a protein that helps stabilize muscle fibers. It is functional when it works properly.
Various gene changes can cause DMD. Medical professionals may also refer to these changes as gene mutations or alterations.
A person’s chances of having a child with DMD depend on whether they or the child’s other parent has any copies of the DMD gene with a change that can cause the condition. Understanding the chances of having a child with DMD can help people make informed choices and plan for their family’s future.
DMD is an X-linked recessive trait. It results from changes in the DMD gene, on the Xp21.2 area of the X chromosome.
People who are male are more likely to develop X-linked recessive conditions, including DMD, than those who are female.
Males typically have an XY genotype, which means they have only one copy of the X chromosome. They develop DMD if their X chromosome has a gene change that causes the condition.
Females have a lower chance of developing DMD because they typically have two copies of the X chromosome. They are likely to develop DMD only if both copies of the X chromosome have gene changes that can cause the condition.
If someone who is female has a DMD gene change on only one of their X chromosomes, they will not develop DMD but will be a carrier of the gene for the condition. The unaffected DMD gene on their second X chromosome helps prevent DMD from developing.
Carriers usually experience no symptoms or only mild symptoms of DMD. However, they can pass the gene to their children, who may develop the condition.
This is the typical inheritance pattern for DMD, but some cases do not fit this pattern.
Some people have de novo gene changes that cause DMD. These are new gene changes that occur spontaneously — a person does not inherit them from either parent.
Also, some people are intersex or have other differences in development that may affect their chances of inheriting a DMD gene change, developing the condition, or passing it to a child.
Most male children who have DMD inherit the condition from their mother, or their XX parent.
Males typically have one X chromosome and one Y chromosome. They inherit the X chromosome from their mother, or XX parent, and they inherit the Y chromosome from their father, or XY parent. If the X chromosome they inherit from their mother has a DMD gene change that causes the condition, they will develop DMD.
Female children rarely develop DMD. However, those who do develop it inherit the DMD gene change from both parents.
Female children typically have two X chromosomes. They inherit one X chromosome from each parent. They usually experience DMD symptoms only if both of their X chromosomes have gene changes that cause the condition.
Some people develop DMD without inheriting it from either parent. In these people, DMD occurs as a result of de novo gene changes, which are spontaneous or new gene changes.
A carrier is someone who has a copy of a gene change that is linked to a health condition but has no symptoms or only minimal symptoms of the condition. They may pass the affected gene to any children they have, and those children will have a chance of developing the condition.
A person with XY chromosomes cannot be a carrier for DMD. If they have a copy of a DMD gene change, they will develop the condition. If they do not have a DMD gene change that causes the condition, they will not develop it.
A person with XX chromosomes can be a carrier for DMD. They will be a carrier if only one of their X chromosomes has a DMD gene change that causes the condition.
While carriers typically do not develop DMD, some may experience symptoms such as increased muscle fatigue and cramps. Carriers also have an increased risk of heart problems.
Some carriers have no signs of DMD and do not know they carry the gene that can cause it.
A person might want to ask their family members whether they have any known relatives with DMD. They should inform their doctor if they have a family history of DMD symptoms.
A doctor may order genetic tests or refer a person to a genetic counselor to find out whether they have any gene changes that can cause DMD. A genetic counselor can help a person understand how any gene changes may affect them and any children they might have.
Having DMD is not the same thing as being a DMD carrier. A person’s chances of having a child with DMD will vary if they or the child’s other parent has DMD rather than being a carrier.
A doctor or genetic counselor can help a person understand their chances of having a child with DMD. A person may want to ask their doctor for a referral to a genetic counselor or search for one online through the National Society of Genetic Counselors.
Yes, it is possible for a child to develop DMD even if neither parent has DMD or is a carrier.
This may happen if the child has a de novo gene change that causes DMD. This is a new gene change that the child did not inherit from either parent. This type of change occurs spontaneously in an egg cell, sperm cell, or embryo.
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A doctor may recommend DMD testing if a child has a known family history of DMD or develops symptoms of DMD, such as muscle weakness that worsens over time.
Heart changes and breathing challenges are
Finding out whether a child has DMD can allow parents or caregivers to seek out treatment earlier. It is also important to identify the specific gene change the child has. Multiple gene changes can cause DMD, and some treatments work better than others for certain gene changes.
Treatment may help people with DMD have a higher quality of life for longer.
DMD is a genetic condition that can pass from parents to children.
It is an X-linked recessive trait that affects males more often than females.
Male children develop DMD if they inherit a single copy of the X chromosome with a DMD gene change that causes the condition. Females rarely develop DMD but may experience the condition only if they have two copies of the X chromosome with DMD gene changes.
Some females are carriers of the DMD gene change. This occurs if they have only one copy of an X chromosome with a DMD gene change. Carriers usually develop few or no symptoms but may pass the gene to their children.
A person can develop DMD without inheriting a DMD gene change from a parent. This can happen if the person has de novo gene changes, or new gene changes that occur spontaneously.
A person who has DMD or has a family history of the condition can talk with their doctor to learn about the chances that their children will have DMD. Their doctor may refer them to a genetic counselor for testing and support.