Fragile X-associated tremor/ataxia syndrome (FXTAS) is a progressive, late-onset (>50 years) multisystem neurodegenerative disorder, associated with an expansion in the 5ʹuntranslated region of the fragile X mental retardation 1 (FMR1) gene that consists of 55-200 CGG repeats, termed the FMR1 gene premutation. While the prevalence of the premutation is 1 in 150-300 females, and 1 in 400-850 males, the penetrance of FXTAS in male carriers is ~40% compared to less than 20% in females.