A novel deletion-insertion mutation identified in exon 3 of FXN in two siblings with a severe Friedreich ataxia phenotype.

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disease most commonly caused by a GAA trinucleotide repeat expansion in the first intron of FXN, which reduces expression of the mitochondrial protein frataxin. Approximately 98% of individuals with FRDA are homozygous for GAA expansions, with the remaining 2% compound heterozygotes for a GAA expansion and a point mutation within FXN. Two siblings with early onset of symptoms experienced rapid loss of ambulation by 8 and 10 years.