The Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene, located on the X chromosome (Xq27.3), contains a polymorphic CGG repeat on its 5’ untranslated region (UTR) implicated in three disorders depending on the repeat number: Fragile X Syndrome (FXS; OMIM #300624) when CGGs > 200, and Fragile X-associated Tremor/Ataxia Syndrome (FXTAS; OMIM #300623) and Fragile X-associated Primary Ovarian Insufficiency (FXPOI; OMIM #311360) [1–3] in the premutation range 55 < CGG < 200. The gene discussed is FMR1; the disease is fragile X-associated tremor/ataxia syndrome.