Genetic Diagnosis in Friedreich Ataxia

Genetic testing is diagnostic in more than 98% of individuals. In more than 95% of abnormal alleles, the mutation is expansion of naturally occurring GAA repeat in first intron (non-coding region) of the frataxin or FRDA gene. GAA repeats: 3-33 – normal; 34-65 – premutation; 66-1700 – abnormal. Less than 5% of abnormal alleles have point mutations in the coding or regulatory regions of the gene. GAA repeat expansion sizes correlate with measures of disease severity; disease-range expansions diminish but do not eliminate frataxin expression. Genetic testing should be performed by an accredited laboratory. GeneTests Web site, a publicly funded medical genetics information resource developed for physicians, other healthcare providers, and researchers, available at no cost. GeneTests hosts an international database of genetic testing laboratories.