KL and fragile X-associated tremor/ataxia syndrome: The present study aimed to investigate the allele frequency of APOε and KLOTHO gene variants (KL-VS) in 245 premutation males over 50 years with and without FXTAS and to investigate the potential role of the allelic variants of these two genes in the pathogenesis of FXTAS, as well their role in the cognitive decline observed in aging premutation carriers.