For Healthcare Professionals

Clinicians who suspect a diagnosis of FA should confirm this through genetic testing from a certified clinical grade laboratory. It is important to note that many genetic tests for FA are repeat expansion analyses of the first intron of the FXN gene, and thus can only detect abnormal GAA repeat expansions, not the less common point mutations, insertions, or deletions found in about 4% of affected individuals. If genetic testing for a patient with suspected FA returns with a repeat expansion detected on only one allele, further testing that sequences the whole FXN gene may be warranted.

Genetic testing should be performed by an accredited laboratory. The NIH Genetic Testing Registry is a publicly funded medical genetics information resource developed for physicians, other healthcare providers, and researchers, available at no cost. You can search this registry for CLIA approved laboratories.

Repeat Expansion Lengths

The length of the GAA repeat expansion determines whether someone is affected by FA:

• 3-33 – unaffected
• 34-65 – premutation
• 66-1700 – diagnostic for FA when biallelic or compound heterozygous with a point mutation, deletion, or insertion on the other allele.

Longer GAA repeat expansions correlate with earlier disease, increased severity of symptoms, and earlier death.

FA is an autosomal recessive disease with prevalence in Europe, North America, South America, North Africa, the Middle East, South Asia, and Australasia. FA is very rare in sub-Saharan African populations and the Far East. The prevalence is highest and best characterized in those of European origin, ~ 1 in 50,000, and a carrier frequency of 1 in 90 individuals.

Carrier testing is recommended for anyone with a positive family history of Friedreich ataxia and for partners of known carriers. Pre-symptomatic testing for at-risk siblings or relatives is available, however, genetic counseling is strongly recommended to assist individuals/families in considering the risks versus benefits of testing a genetic condition with one recently approved treatment that is not available yet globally. Visit the FA Clinical Care Guidelines to learn more about best practices for genetic counseling and testing.