Friedreich ataxia (FRDA OMIM #229300) is a slowly progressive ataxia that is inherited in an autosomal recessive manner. Ninety-six percent of affected individuals have a homozygous GAA triplet-repeat expansion (between 200 and 900 copies, normal is 7-20 copies) in the first intron of the FRDA gene (OMIM # 606829) while the remaining four percent of affected individuals are compound heterozygotes with a GAA expansion in one allele and another gene mutation in the other allele.

Our collection of FRDA cell lines came from fifty individuals, twenty-six of whom are affected with FRDA. There are sixteen affected females and ten affected males ranging in age from thirteen to fifty-three years. The twenty-four unaffected individuals have relatives that are affected with FRDA. Of the twenty-six affected individuals, twenty-five have known GAA repeat sizes and all are homozygous for the GAA expansion. Of the twenty-four unaffected individuals, there are twenty-two known carriers with documented GAA repeat sizes.