FMR1 and fragile X-associated tremor/ataxia syndrome: The most severe form of clinical disorder associated with premutation expansions (55–200 CGG repeats) in the 5′ untranslated region of the Fragile X Mental Retardation 1 (FMR1) gene is a late-onset progressive neurodegenerative condition: Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS) (1).