Fragile X-associated tremor/ataxia syndrome (FXTAS, OMIM# 300623) is a late-onset neurodegenerative disorder that appears in adult FMR1 (Fragile X Messenger Ribonucleoprotein 1) premutation carriers (55–200 CGGs). The gene discussed is FMR1; the disease is fragile X-associated tremor/ataxia syndrome.