Complete FXN deletion in a patient with Friedreich's ataxia

Most patients (98%) with Friedreich's ataxia (FRDA) are homozygous for the GAA repeat expansion in FXN. Only a few compound heterozygous patients with an expanded repeat on one allele and a point mutation or an intragenic FXN deletion on the other allele are described. In a minority of the patients only a heterozygous pattern of the repeat expansion can be detected. Using array analysis after GAA repeat expansion testing, we identified a FRDA patient who is compound heterozygous for an expanded GAA repeat and a complete FXN deletion. Since not only repeat expansions and point mutations, but also large rearrangements can be the underlying cause of FRDA, a quantitative test should also be performed in case a patient shows only one allele with an expanded GAA repeat in FXN.