Friedreich ataxia (FRDA) is an autosomal recessive disorder characterized by neurodegeneration and cardiomyopathy, and is the most common inherited ataxia. About 98% of individuals with FRDA are homozygous for an expansion of a GA A trinucleotide repeat sequence within the first intron of the FXN gene. The remaining individuals are compound heterozygotes for a GAA expansion and a point mutation. Pathogenic GAA expansion alleles are in the size range of 60 to >1300 repeats. The presence of a GAA repeat expansion results in the inhibition of FXN gene expression, reduced levels of full-length FXN transcript, and an insufficiency of the mitochondrial protein frataxin (1–4). Overall, an inverse correlation has been found between the size of the smaller GAA expansion and transcript levels, the amount of residual frataxin produced, and the age of onset of disease symptoms (5–9).