Genetic testing, often via a blood sample, can confirm a muscular dystrophy diagnosis. It can also identify specific gene mutations to help guide treatment and determine whether or not someone is a carrier for the condition.

Muscular dystrophy (MD) is a group of disorders that cause progressive loss of muscle mass and function.

Most types of MD are due to gene changes called mutations. The mutations responsible for MD interfere with your body’s ability to manufacture the proteins required to maintain healthy muscles.

Genetic testing is a tool healthcare professionals use to help diagnose MD and determine the appropriate treatment. They can also use it to help people with a family history of MD who are concerned about passing the condition on to their children.

This article explores everything you need to know about gene testing for MD.

Genetic testing can help determine if you or your child has a mutation associated with MD. There are a few reasons why a doctor might suggest this kind of test.

Diagnosis

Genetic testing can confirm an MD diagnosis. Doctors typically use it when signs and symptoms such as muscle weakness and problems with coordination are already present, and the results of other diagnostic tests point to MD.

Carrier testing

Several types of MD can be passed on via genetic carriers who don’t have any outward signs of the condition. For example, if you or your partner have a family history of MD, carrier testing can help you determine whether you are at risk of passing the condition on to your children.

Prenatal diagnosis

Healthcare professionals typically recommend prenatal screening tests during pregnancy if there is a chance the fetus might have the genetic mutation for MD. If the fetus has the mutation, they are likely to develop MD at some point after birth.

Treatment

Some targeted therapies for MD are already available, and many more are currently in development. Doctors must rely on genetic testing to be able to prescribe these types of treatments because they target specific mutations.

Genetic types of muscular dystrophy

Most types of MD are due to genetic mutations passed on from parents to children. In rare cases, genetic mutations occur spontaneously or without a clear pattern of inheritance.

The following table lists the genes responsible for some of the most common types of muscular dystrophy.

Type of muscular dystrophyGene(s)
Duchenne muscular dystrophy (DMD)dystrophin
Becker muscular dystrophy (BMD)dystrophin
Congenital muscular dystrophy (CMD)laminin-alpha 2 (LAMA2) and others
Myotonic muscular dystrophydystrophia myotonica protein kinase (DMPK)
Limb-girdle muscular dystrophycalpain-3 (CAPN3) and others
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Most genetic tests require you or your child to provide a DNA sample via your bodily fluids. Sometimes, you can take a saliva sample at home using a test kit. Other times, you may provide a blood sample in a healthcare setting.

Prenatal genetic testing requires a sample of the amniotic fluid, a process called amniocentesis, or the placenta, a process called chorionic villus sampling.

You’ll provide a DNA sample which will undergo analysis in a lab. If a specific MD mutation is known to run in your family, the lab technicians will look for that mutation.

If the mutation isn’t known, the analysis will first look for larger mutations, including deletions and duplications. If nothing is found, your doctor might suggest another genetic test to look for smaller mutations.

Your doctor will receive the results of your or your child’s genetic test and will contact you to discuss the next steps.

  • If the test revealed a genetic mutation linked to MD, you or your child likely has MD.
  • If the test did not reveal a genetic mutation linked to MD, your doctor may want to run additional tests to understand what is causing the symptoms. There is a small chance that MD is still the cause, even if no genetic mutation was found.

Genetic testing is just one part of the diagnosis process for MD. Some other common tests include:

How accurate is genetic testing for muscular dystrophy?

The accuracy of genetic tests varies a lot. It depends on the type of test and the purpose.

For example, a result indicating an MD mutation is unlikely to be wrong in someone who already has symptoms and other tests to support an MD diagnosis.

In addition, genetic tests that focus on a known mutation that runs in your family are more likely to produce an accurate result.

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Muscular dystrophy can be passed on from one generation to the next in several ways:

  • Autosomal dominant inheritance: Only one parent needs to have the genetic mutation for the child to develop the condition. Some rarer forms of MD, including facioscapulohumeral MD and myotonic MD, are passed on this way.
  • Autosomal recessive inheritance: Both parents need to provide the mutation for the child to develop the condition. Most types of CMD are passed on in an autosomal recessive fashion.
  • X-linked inheritance: DMD and BMD are X-linked disorders. That means they are passed on via a mutation on the X chromosome from biological mothers (who are carriers but do not have the condition) to their male children.

Your risk of inheriting MD depends on the type.

DMD is the most common type, mostly affecting people assigned male at birth. BMD is also more common in males as it is also an X-linked condition.

People with XY chromosomes are more likely than those with XX chromosomes to have the condition. This is because they don’t have a second copy of the X chromosome, so inheriting one copy with the DMD mutation will cause the condition.

MD types that are autosomal (not X-linked) do not seem to affect one sex disproportionately.

Because some genetic mutations may be more common in specific populations, people of certain races or ethnicities may be more likely to inherit MD.

According to the Centers for Disease Control and Prevention (CDC), DMD and BMD are much more common in Hispanic people and non-Hispanic white people than in Black people.

See below for some common questions about genetic tests for MD.

How long does genetic testing for muscular dystrophy take?

It can take several weeks to receive the results of a genetic test. Your doctor will let you know when your results are ready.

Which parent carries the muscular dystrophy gene?

The most common types of MD are X-linked, which means they are passed on from biological mothers to their male offspring via the X chromosome.

How likely is my child to have muscular dystrophy if I’m a carrier?

The likelihood of a child inheriting MD depends on the type since there are different patterns of inheritance. In DMD, the male child of a female carrier has a 50% chance of inheriting the disorder.

Can you get muscular dystrophy if your parents don’t have it?

Yes, one or more of your parents can carry a genetic mutation linked to MD without showing symptoms themselves.

Doctors use genetic testing to diagnose MD, an inherited disorder that causes progressive muscle weakness. DMD and BMD are two of the most common types.

A genetic test requires a sample of your DNA from blood, saliva, or another fluid. Your doctor can help you learn more about the testing process and what to expect.