FXN and Friedreich ataxia: In FRDA patients, GAA1 and GAA2 correlated inversely with frataxin levels (p<0.0001, R2 = 0.4632; P<0.001, R2 = 0.3886; Figure 2A–B), whereas age at onset correlated directly with frataxin levels (p<0.001, R2 = 0.3577; Figure 2C).