GAA trinucleotide repeat expansion in variant Friedreich's ataxia families

Phenotypic variants in Friedreich's ataxia include late onset, preservation of the lower limbs tendon reflexes, and slow progression. We describe clinical and electrophysiological features from three families with Friedreichlike phenotypes. Friedreich's ataxia diagnosis was confirmed by finding two allelic expansions of the GAA trinucleotide repeat at the X25 gene. In family 1 both patients had a late-onset phenotype with preservation of knee and ankle jerks, lack of cardiomyopathy, and preserved H reflex. One of them did not have electrophysiologic evidence of sensory axonal neuropathy. Patients from family 2 showed variability in the age of onset, and 2 out of 3 affected children had hyperactive lower limbs reflexes with preserved H reflex. Disease progression in a patient from family 3 was very slow after onset at the age of 21. The finding of two expanded alleles in these families confirms the wide variability of the clinical spectrum of Friedreich's ataxia.