Why do some Friedreich's ataxia patients retain tendon reflexes? A clinical, neurophysiological and molecular study

Among 101 patients homozygous for GAA expansion within the X25 gene, 11 fro m 8 families had Friedreich's ataxia with retained reflexes in the lower li mbs (FARR). These patients had a lower occurrence of decreased vibration se nse, pes cavus, and echocardiographic signs of left ventricular hypertrophy than the 90 FA patients with areflexia. The mean age at onset was signific antly later (26.6 +/- 11.4 vs. :14.2 +/- 6.9 years), and the mean size of t he smaller allele was significantly less (408 +/- 252 vs. 719 +/- 184 GAA t riplets) in FARR patients. The neurophysiological findings were consistent with milder peripheral neuropathy and milder impairment of the somatosensor y pathways in FARR patients.