Understand Test Results

Understanding genetic testing for Duchenne.

The latest genetic testing methods can identify specific mutations in the dystrophin gene. Identifying your child’s mutation will allow your doctor to determine amenability to EXONDYS 51. Patients with Duchenne who receive EXONDYS 51 must have a genetic test that shows a mutation in the dystrophin gene that can be treated by skipping exon 51.


Meet Ricky, age 19
Deletion of exons 45-50

Getting familiar with genetic test reports.

After your child provides a blood or saliva sample, your doctor will send your child’s genetic sample to a lab to run the genetic test report. Each lab’s report looks a little different. Here are some of the key pieces of information you should be looking for as you read the genetic test report with your child's doctor:


  1. A Duchenne diagnosis.

    The genetic test report will identify if there are any mutations in the dystrophin, or DMD, gene that would confirm a Duchenne diagnosis.

    What to look for: A confirmation that there is a mutation on the dystrophin, or DMD, gene. You might see terms like “Positive result,” “Mutation detected,” “Pathogenic variant detected,” or similar terms.

  2. The type of mutation.

    The test will provide information on the type of mutation in the dystrophin gene. There are three types of mutations:

    • Large deletions: One or more exons are missing. This is the most common type and includes the ones targeted by EXONDYS 51.
    • Large duplications: One or more exons are copied.
    • Other changes: Small changes in the gene that do not include an entire exon.

    What to look for: An indication that the type of mutation is a “deletion.”

  3. The missing exons.

    Your child’s doctor or genetic counselor will determine amenability to exon 51 skipping based on which exons are missing. If the genetic test report mentions deletions, it will also identify the “genomic region” or simply add a range of missing exons (e.g., 48-50).

    What to look for: A number or number range stating which exons make up the deletion.

Icon Alert

Not all genetic tests are created equal. While testing technology has advanced steadily over the last few years, older methods are still in use that may not yield the most accurate results. Ask your child’s doctor to ensure that the lab used for genetic testing employs the latest methods.

Discuss test results with your child's doctor or genetic counselor.

Whether your child has had a recent test, or you want to reexamine an older one, make sure to review the results with your child's doctor or genetic counselor as soon as possible to determine amenability to EXONDYS 51. In your conversation, you may want to ask:


  • Did the test confirm Duchenne muscular dystrophy?
  • What’s the type of genetic mutation?
  • Does my child’s deletion show amenability to exon 51 skipping?
  • Is EXONDYS 51 the right treatment option for us?

Create a customized Doctor Discussion Guide.

Answer a few simple questions and we’ll create a printable guide for your child’s next doctor visit, with helpful information about what to ask during the appointment.

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Related FAQs

What is a genetic mutation?

A mutation is a change in a person's DNA. Mutations range in size from a small (a single rung on a ladder) to a large segment of DNA. Every mutation causes a different effect on our bodies. Learn more about the role of genetics in Duchenne.

What does “amenable” mean?

Amenability describes the potential for your child to be treated with exon-skipping therapy. EXONDYS 51 is only for those whose Duchenne muscular dystrophy is the result of a genetic mutation amenable to exon 51 skipping. Find out more about genetic testing for Duchenne.

Why is a Duchenne diagnosis important?

Because Duchenne is a progressive disease, it’s important for your child's doctor to confirm a diagnosis and identify the specific genetic mutation to guide your child's care and treatment. More about the steps to diagnosis.



WHAT IS EXONDYS 51 (eteplirsen)?

EXONDYS 51 is used to treat Duchenne muscular dystrophy (DMD) in patients who have a confirmed mutation in the dystrophin gene that can be treated by skipping exon 51. EXONDYS 51 was approved under accelerated approval. Accelerated approval allows for drugs to be approved based on a marker that is considered reasonably likely to predict a clinical benefit. EXONDYS 51 treatment increased the marker, dystrophin, in skeletal muscle in some patients. Verification of a clinical benefit may be needed for EXONDYS 51 to continue to be approved.

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Allergic reactions, including wheezing, chest pain, cough, rapid heart rate, and hives have occurred in patients who were treated with EXONDYS 51. Seek immediate medical care if signs and symptoms of allergic reactions occur.

Side effects that happened at least 25% more often in 8 patients treated with EXONDYS 51 by intravenous infusion than in 4 patients treated with an inactive intravenous infusion were problems with balance (38%, 0%), vomiting (38%, 0%), and skin irritation (25%, 0%). The most common side effects were problems with balance and vomiting.

The most common side effects seen in greater than 10% of patients receiving EXONDYS 51 (N=163) in other clinical trials were headache, cough, rash, and vomiting. 

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit www.fda.gov/medwatch or call 1-800-FDA-1088. You may also report side effects to Sarepta Therapeutics at 1-888-SAREPTA (1-888-727-3782).

Please see the full Prescribing Information for EXONDYS 51 (eteplirsen).