FMR1 and fragile X-associated tremor/ataxia syndrome: The prevalence of the FMR1 premutation causing FXTAS is 1 in ~290 women and 1 in ~850 men (Hunter et al., 2014), but the penetrance is around 40% in men and 8–16% in women aged over fifty (Jacquemont et al., 2004; Coffey et al., 2008; Rodriguez-Revenga et al., 2009).