"My child has been diagnosed with Duchenne muscular dystrophy, and I want to learn about how genetics plays a role in the disease."
Genetics is the study of heredity, the process by which parents pass certain genes to their children. Many characteristics are determined by genes, including physical appearance, natural talents, and the likelihood of getting certain diseases.
Genetic testing is important because it is used to confirm the majority of Duchenne diagnoses and can help identify the specific type of mutation that is causing a child’s Duchenne muscular dystrophy.
There are several types of dystrophin gene mutations that cause Duchenne:
- Deletion mutations
- Duplication mutations
- Small mutations
There are disease management strategies being developed that depend on the mutation type. Therefore, knowing the mutation type can affect which strategies are appropriate for a child.
Genetic testing can be done with a simple blood test.
Genetic testing is a 2-part process:
- First, the blood sample is analyzed to determine the presence of a deletion or duplication mutation in the dystrophin gene. This first test can tell what kind of genetic mutation is the cause of Duchenne in about 75% of cases
- If no deletion or duplication mutation is identified during the first part of the process, a second genetic test consisting of full gene sequencing can reveal the specific small mutation that is the genetic cause of a child’s Duchenne
Full gene sequencing is the only way to know if a person has a small mutation, such as nonsense mutation Duchenne muscular dystrophy.
The results of genetic testing provide specific information about the change in the DNA or mutation that is causing Duchenne.
Whether 1 or 2 genetic tests are required to detect the specific mutation that is causing Duchenne, it is important to fully understand the specific mutation because knowing it could affect how the disease is managed. Disease management strategies that depend on the specific mutation type are in development.
Genetic testing, including full gene sequencing, if needed, is important. Knowing the exact mutation might help determine the appropriate disease management strategies.
It is important for a family to speak with a genetic counselor. While it is possible for a family with no history of Duchenne to have a child with the disease, Duchenne often runs in a family.
Duchenne is inherited in an X-linked pattern, meaning that a gene that may contain a mutation causing a disease is on the X chromosome. Every person has 23 pairs of chromosomes; each carries the genes that make us who we are. One of these pairs of chromosomes determines gender. A boy inherits an X chromosome from his mother and a Y chromosome from his father, while a girl gets two X chromosomes, one from each parent.
If a mother has the mutation that causes Duchenne on one of her X chromosomes, she is called a carrier. That means there is a chance she can pass the genetic mutation on to her children. Because boys only have one X chromosome, if they receive the genetic mutation, they will have Duchenne. If a girl inherits the genetic mutation, however, she will be a carrier like her mother. Girls are less likely than boys to be affected by Duchenne because their unaffected X chromosome helps protect against developing the disease. There is a small chance, however, that girls may experience symptoms of Duchenne.
X = X chromosome
X = Affected X chromosome
Y = Y chromosome
A genetic counselor provides support and education for families throughout the genetic testing process. A genetic counselor can help a family understand what the information means to them and whether other female relatives should be tested to determine if they are also carriers.
If your child has not yet had genetic testing, or requires gene sequencing to identify a specific mutation, visit Decode Duchenne.
New disease management strategies are being developed to treat specific mutations in the dystrophin gene. A genetic counselor can help interpret the results of a genetic test to determine which disease management strategies may be appropriate for that person.