GAA TRINUCLEOTIDE REPEAT EXPANSION IN VARIANT FRIEDREICHS ATAXIA FAMILIES

Phenotypic variants in Friedreich's ataxia include late onset, preserv ation of the tower limbs tendon reflexes, and slow progression. We des cribe clinical and electrophysiological features from three families w ith Friedreichlike phenotypes. Friedreich's ataxia diagnosis was confi rmed 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, an d preserved H reflex. One of them did not have electrophysiologic evid ence of sensory axonal neuropathy. Patients from family 2 showed varia bility in the age of onset, and 2 out of 3 affected children had hyper active lower limbs reflexes with preserved H reflex. Disease progressi on 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. (C) 1997 John Wiley & Sons, Inc.