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Diagnostic Services

Genetics Lab


Friedreich Ataxia Mutation Analysis

Friedreich ataxia (FA) is a slowly progressive ataxia with typical onset between age 10-25 years. It is characterized by depressed tendon reflexes, speech disturbance (dysarthria), muscle weakness, visual disturbance due to optic nerve atrophy and spasticity. Individuals with FA often have diabetes mellitus and/or cardiomyopathy. For about 25% of affected individuals, the age of onset is later and progression of the disease is much slower than usual.

FA is caused by a GAA expansion in the Frataxin gene. Normal GAA repeat length is 5-33 GAA repeats. 34-65 uninterrupted GAA repeats are mutable normal alleles. They do not cause disease, but may expand during transmission to the next generation and become disease-causing alleles. Disease-causing alleles have 66-1700 repeats.

96% of affected individuals are homozygous for a triplet repeat expansion. About 4% of affected individuals will have a GAA expansion on one allele and a point mutation on the other allele.

Test Name: Friedreich Ataxia (GAA expansion only)
Test Code:
Test Description:
Molecular analysis of the Frataxin gene for GAA repeat length.
The test is indicated for:
-Individuals with a suspected diagnosis of Friedreich ataxia
-Individuals with a family history of FA who want carrier testing
-Individuals in the general population who want carrier testing
Related Tests:
Clinical Links: Friedreich Ataxia GeneReview
Mon - Fri
Turnaround Time:
1-2 weeks
Reference Range:
Interpretive report provided
Consent Form:
Sample Requirements: Type
Whole Blood: 1-3 ml EDTA (purple) or ACD (yellow) tube.
DNA: 5-10ug extracted DNA

Keep specimen at room temperature. Do not spin.

Ship overnight at room temperature.
Samples Received:
Mon - Fri 8:00am - 5:00pm
Special Considerations:
Point mutations are not detected by this method.
Please e-mail Lab Client Services ( or call at 206-987-2617 with any billing questions
CPT Code:
Please e-mail Lab Client Services ( or call at 206-987-2617 with any billing questions