Phenotypic variability in friedreich ataxia: Role of the associated GAA triplet repeat expansion

Laura Montermini, Andrea Richter, Kenneth Morgan, Cristina M. Justice, Dominique Julien, Barbara Castellotti, Jocelyne Mercier, Josée Poirier, Fiorentino Capozzoli, Jean Pierre Bouchard, Bernard Lemieux, Jean Mathieu, Michel Vanasse, Marie Hélene Seni, Gail Graham, Frederick Andermann, Eva Andermann, Serge B. Melançon, Bronya J B Keats, Stefano Di DonatoMassimo Pandolfo

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Abstract

We studied genotype-phenotype correlations in a group of 100 patients with typical Friedreich ataxia (FRDA), and in three groups of patients with atypical clinical presentations, including 44 Acadian FRDA, 8 late-onset FRDA (LOFA), and 6 FRDA with retained reflexes (FARR). All patients, except 3 with typical FRDA, carried two copies of the FRDA-associated GAA triplet repeat expansion. Overall, the phenotypic spectrum of FRDA appeared to be wider than defined by the currently used diagnostic criteria. Our study indicated the existence of several sources of variability in FRDA. Patients with larger GAA expansions tended to have earlier onset and were more likely to show additional manifestations of the disease. Mitotic instability of the expanded GAA repeats may partially account for the limited degree of correlation between expansion sizes as determined in lymphocytes and clinical parameters. Some clinical variants associated with specific FRDA haplotypes, such as Acadian FRDA and FARR, turned out to be unrelated to expansion sizes. No polymorphism in the frataxin coding sequence could be associated with these clinical variants.

Original languageEnglish
Pages (from-to)675-682
Number of pages8
JournalAnnals of Neurology
Volume41
Issue number5
DOIs
Publication statusPublished - May 1997

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ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Montermini, L., Richter, A., Morgan, K., Justice, C. M., Julien, D., Castellotti, B., Mercier, J., Poirier, J., Capozzoli, F., Bouchard, J. P., Lemieux, B., Mathieu, J., Vanasse, M., Seni, M. H., Graham, G., Andermann, F., Andermann, E., Melançon, S. B., Keats, B. J. B., ... Pandolfo, M. (1997). Phenotypic variability in friedreich ataxia: Role of the associated GAA triplet repeat expansion. Annals of Neurology, 41(5), 675-682. https://doi.org/10.1002/ana.410410518