Carriers of the fragile X premutation, an allelic variant of the FMR1 gene with 55–200 cytosine-guanine-guanine (CGG) repeats, are at risk of developing a late-onset, progressive neurodegenerative disease—fragile X-associated tremor/ataxia syndrome (FXTAS). Here, FMR1 is linked to fragile X-associated tremor/ataxia syndrome.