Skip to content
Friedreich's Ataxia News logo
  • Forums
  • About FA
    What is FA?
    Causes
    Symptoms
    • Cardiomyopathy
    Diagnosis
    Treatments
    • Approved treatment: Skyclarys
    • Experimental Treatments
    • Non-drug Treatments
  • News
  • Columns
    Defining Yourself — Jean Walsh
    My Darling Disability
    — Kendall Harvey
    Little Victories — Matthew Lafleur
    Recalibrating – Elizabeth Hamilton
    Archived Columns
    • No Good Excuse — Sean Baumstark
    • Hope from Home — Katie Griffith
    • An Unexpected Journey — David Riley
    • Practical Guide to Life with FA — Christina Cordaro
  • FA education
    Videos: Start strong, stay steady
    My FA diagnosis story
    Growing up with FA
    Talking to your child about FA
    Assistive equipment, aids, and adaptations
    Guidance for parents of children with FA
    FA treatment options
    Exercise and physiotherapy
    Living with FA
    FA support and resources
    FA and mental health
    Essential travel tips
    Speech therapy
    AAC devices
    Occupational therapy
    FA and diet
    Late-onset FA
    Aging with FA
  • Find a physician
  • For professionals
  • Advocacy partners
  • What can we help you find today?

    • Forums

Choosing the right genetic testing for Friedreich's ataxia

Sub Subramony, MD, discusses the types of genetic testing that are most effective when diagnosing a potential Friedreich’s ataxia case, and the science behind them.

About Sub Subramony, MD

Sub Subramony, MD, is a board-certified neurologist and neuromuscular medicine specialist at the Norman Fixel Institute for Neurological Diseases at University of Florida Health. He also serves as a professor in the University of Florida Department of Neurology with a joint appointment in pediatrics. His area of focus is genetic neuromuscular diseases, including Friedreich’s ataxia.

Transcript

Friedreich’s ataxia, of course, is detected by a targeted approach to DNA analysis for the Friedreich’s mutation. Friedreich’s ataxia is caused by an unusual mutation, which is an expansion of a triplet-repeat GAA in the frataxin gene.

The reason I bring this up is the fact that this type of repeat expansion is not detected by commonly used sequencing methodology. Increasingly for detection of many genetic diseases, the DNA is subjected to a sequencing methodology using appropriate equipment.

And this kind of sequencing technology simply looks at all the molecules that make up your gene, make up the DNA of interest. But this technology is useful because it can actually assess a large number of genes, like a couple hundred genes, or the entire coding portion of the gene, which is called the exome sequencing.

But those kind of technologies will not detect Friedreich’s ataxia. You need a different technology, such as Southern blot and PCR.

So unless you specifically ask for Friedreich’s ataxia and you just go for a sequencing technology, thinking that, “I can try to look at a large number of genes with one test,” you’re gonna miss Friedreich’s ataxia.

Now, about 96 or 97% of patients with Friedreich’s ataxia have this repeated — repeat — expansion called the GAA expansion on both copies of the frataxin gene. That is the maternal and paternal copy. But in about 3-4%, only one copy is expanded and the other copy then has a conventional mutation, which can be detected by sequencing technology. So the trick here is, of course, if you have a patient that looks as if he or she has Friedreich’s ataxia and your test detects only one expanded allele, the other allele will have to be sequenced.

So basically, what you start out with is looking for the GAA expansion in both alleles. And then if that’s positive, you have your diagnosis. If only one allele is expanded and your patient looks as if he or she has Friedreich’s ataxia, the other allele is subjected to a sequencing methodology to look for a conventional mutation. And many of the laboratories that offer Friedreich’s testing automatically will do this for you.

Our FA medical advisor

Dr. David LynchDavid Lynch, MD, PhD, is the director of the Friedreich’s Ataxia Program at Children’s Hospital of Philadelphia.

Meet the expert

Newsletter driver

Envelope icon

Subscribe to our newsletter

Get regular updates to your inbox.

This field is for validation purposes and should be left unchanged.

Bionews, Inc.

3 W Garden St
Suite 700
Pensacola, FL 32502
Website: bionews.com
Email: [email protected]
Phone: 1-800-936-1363

  • About Us
  • Leadership
  • Our Culture
  • Editorial Policy
  • Advertising Policy
  • Corrections Policy
  • Terms of Service
  • Privacy Policy
  • Careers
  • Contact Us
Disclaimer

This site is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

Copyright © 2013-2025 All rights reserved.