FRIEDREICHS ATAXIA WITH RETAINED TENDON REFLEXES - MOLECULAR-GENETICS, CLINICAL NEUROPHYSIOLOGY, AND MAGNETIC-RESONANCE-IMAGING

Lower limb areflexia is generally regarded as an essential criterion f or the diagnosis of Friedreich's ataxia (FRDA). We describe a family w ith a recessive form of early-onset ataxia in which one member had a p henotype typical of FRDA whereas another, with retained tendon reflexe s in the lower limbs, did not have electrophysiologic evidence of the usual severe afferent axonal neuropathy of FRDA. In contrast, somatose nsory evoked potentials, eye-movement recordings, and MRI of the head and cervical cord provided results highly suggestive of FRDA in both p atients. We performed genetic linkage analysis in this family, using m arkers tightly linked to the FRDA locus on chromosome 9. Inheritance o f identical paternal and maternal genotypes by the affected members, b ut not by their unaffected siblings, provided supporting evidence that this disorder may result from mutation within the FRDA gene or is tig htly linked to the investigated loci on chromosome 9.