Spinocerebellar ataxia 27 (SCA27) has recently been associated with long GAA expansions in the first intron of the FGF14 (fibroblast growth factor 14) gene. The aim of our study was to determine the presence of pathogenic GAA expansions in the FGF14 gene in Slovenian patients with unexplained ataxia. In our study, we included 103 patients with genetically unexplained ataxia. For genetic testing, we used polymerase chain reaction (PCR) and confirmed the presence of GAA repeats with Sanger sequencing analysis. In the first phase, we used PCR to determine the repeat length, which was successful in 101 (98 %) patients. With patients who showed fragments larger than the normal GAA repeat range on at least one allele, we performed additional sequencing analysis. We identified heterozygous pathogenic expansions longer than 300 repeats in five patients (4,9 %), confirming the presence of GAA-FGF14 ataxia in these patients. In two patients (2,0 %), we detected alleles with repeats in the reduced penetrance range (between 250 and 300 GAA repeats). In total, GAA repeat expansions were the likely cause of ataxia in seven (6,9 %) Slovenian patients with unexplained ataxia, which is comparable to the prevalence reported in other populations. Our study confirms that pathogenic GAA expansions in the FGF14 gene are also present in the Slovenian patients with ataxia. The diagnostic methods used proved to be reliable and effective in detecting these mutations, significantly contributing to the improvement of genetic diagnostics and the understanding of the molecular basis of ataxia.
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