Identical mutation associated with distinct clinical phenotypes of Friedreich’s ataxia: case report

Friedreich’s ataxia is an autosomal recessive disease and the most frequent inherited ataxia. The disease is characterized byexpression of the unstable GAA trinucleotide repeat expansion located in the fi rst intron of the FXN gene on chromosome 9. Clinically,it is presented by progressive gait and limb ataxia, absent refl exes with positive Babinski, and cardiomyopathy with no diff erenceregarding race and gender. Our patients are teenage siblings in whom analysis of DNA confi rmed both alleles with full mutationin the FXN gene that codes for frataxin. Even though both siblings have full mutation and are both in the same age group, theirclinical presentation and course of the disease are rather diff erent. The sister has almost all typical neurologic signs of Friedreich’sataxia with progressive course despite supportive therapy. The brother shows only hypertrophic cardiomyopathy with no neurologicor skeletal disturbances so far. It is possible that other factors may also play an important role in the clinical presentation andcourse of Friedreich’s ataxia. The cases of our patients prove that it is not advisable to foresee the clinical course based solely on thenumber of repeats.

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