Genetic Testing for Periodic Paralysis

Periodic paralysis is a genetic disorder, which means that people who have the disorder have a mutation in their genes.

This mutation causes muscle cells to incorrectly use things like sodium, potassium, etc that need to go in and out of the cells. Because these muscle cells aren’t working correctly, the muscles aren’t able to move very much. This is what’s called a paralysis attack.

Many people who have periodic paralysis don’t know that they have it. They are confused by their unexpected attacks of paralysis and muscle weakness. Doctors often don’t know how to diagnose periodic paralysis because they have never heard of it, so some periodic paralysis sufferers don’t get diagnosed for years — or at all.

If you or a loved one are experiencing symptoms that may be periodic paralysis, but you aren’t sure, you might want to consider a genetic test. Since it is a genetic disorder, a genetic test might detect it. Genetic tests have their pros and cons, so read below to learn the details of what you can expect from a genetic test.

How is a genetic test performed?

 

Step 1– In The Doctor’s Office

  • Your doctor or genetic counselor will talk to you about the test, what it may or may not tell you, insurance coverage, and risks of insurance discrimination.
  • You may have to sign a consent form depending on the lab performing the test.
  • Your doctor or nurse will get a sample from you. Samples are usually saliva, fluid around the baby during pregnancy
  • You may be asked to give another sample if the first sample does not work.
  • The sample is sent to the lab.

 

Step 2– Preparing your DNA

  • The lab will get your DNA from the sample to test.
  • To find the cause of a disease, the lab can use different ways to look at all or part of your DNA. The way the lab looks at your DNA will depend on the type of genetic test your doctor ordered.

 

Step 3– Sequencing your DNA

  • Sequencing tests read your DNA and look for variants (changes) in the DNA.
  • Sequencing tests can give detailed information about:< >Specific genes and DNA variants (targeted sequence capture) All of the genes that make proteins in a person (whole-exome sequencing) All of the DNA in your genome (whole genome sequencing). The human genome is made of DNA and contains all of a person’s genetic information (like a set of books). The lab may put all or part of your DNA on a machine called a DNA sequencer.
  • The DNA sequencer reads your DNA and collects data known as short “reads.” Each “read” represents a very tiny part of your total DNA sequence (each read is like a page in a book).

 

Step 4– Analyzing your DNA

  • Computers are used to put all of the pieces (reads) of your DNA together (like putting the pages of the book in the right order).
  • Computers are used to compare your DNA to all of the DNA in the human body (the human reference genome).
  • The lab gets a report from the computers, which lists any variants in your DNA.
    • We all have DNA changes (variants) VUS
    • Some DNA variants cause disease (like a word spelled wrong); other variants do not cause disease (like a word with different spellings: grey and gray).
    • We do not know what every DNA variant means at this time. (70% of periodic paralysis mutations are known) A negative test DOES NOT MEAN YOU DO NOT HAVE PERIODIC PARALYSIS. YOUR MUTATION IS JUST NOT KNOWN YET!

 

Step 5– Interpreting your DNA

  • A team of experts talks about and analyzes your results. Doctors, scientists, genetic counselors, and computer experts are all on the team (like a group of people sitting down to read and talk about a book).
  • To decide which variant causes the disease you are interested in, the team looks at your results (your list of variants), your symptoms, and your family history.
  • The team may or may not be able to find the cause of the disease you are interested in.
  • If the team finds the cause of the disease, they confirm the result with a different test.
  • Some reasons why the team may not be able to find the cause of the disease can be:
    • Some parts of the DNA cannot be sequenced.
    • Not enough is known about the disease at this time.
    • The test that was performed did not look at the part of your DNA that is causing the disease, and a different test needs to be ordered.
    • The team was not given enough information about your symptoms or family history to interpret the results.

 

Step 6– Receiving your results

  • The lab will give the written results back to your doctor or genetic counselor. Results of clinical tests will go in your medical record. Research study results do not go in your medical record.
  • Your doctor and/or genetic counselor will tell you the results and answer your questions.
  • Your doctor may need to perform more medical or genetic testing based on the results of your test.
  • The amount of time to get your test results can vary.
  • Always get a complete copy of your results and share them at Ask the Experts if your mutation comes back as a VUS

Where To Get A Genetic Test for Periodic Paralysis

No-charge Periodic Paralysis Gene Panel Testing Program

Strongbridge Biopharma® (now Xeris Biopharma™️) has partnered with Invitae to offer a periodic paralysis gene panel test for those who have episodic muscle weakness or temporary paralysis provoked by common triggers for primary hyperkalemic or hypokalemic periodic paralysis. 

The PPA endorses Strongbridge as our preferred resource for genetic testing of periodic paralysis. However, we provide other options as we become aware of them. We like our members to have choices. If you know of a lab that you trust and would like us to add it to the list, please send us a message.

Dante Labs – Genetic Testing in Europe

Their vision is to make advanced genomics accessible to everyone. This is why they pioneered the genomics-as-a-service concept, implementing it in their new European sequencing center. By leveraging advanced data analysis algorithms and new DNA sequencing techniques, they can offer personalized reports and continuous updates. Click here to learn more about Dante Labs.

We hope this article helped you shed some light on periodic paralysis genetic testing. While genetic testing isn’t a completely perfect way to detect periodic paralysis, it is still an important method. Feel free to contact us with any questions, and we’ll do our best to help you.

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