FMR1 and fragile X-associated tremor/ataxia syndrome: Furthermore, PM alleles are associated with a significant elevation of FMR1 mRNA levels [11, 12] and it has been shown that carriers of the FMR1 premutation are at risk of developing fragile X-associated tremor/ataxia syndrome (FXTAS), a late-onset neurodegenerative disorder usually affecting males over 50 years of age [13].