FMR1 and fragile X syndrome: FXDs occur in individuals with a CGG repeat expansion in the 5′ untranslated region of FMR1 [62], and they include Fragile X syndrome (FXS) (>200 CGG repeats, referred to as “full mutation”) [63], Fragile-X-associated tremor/ataxia syndrome (FXTAS) (55–200 CGG repeats, referred to as “premutation”), and Fragile-X-associated primary ovarian insufficiency (FXPOI) (premutation) [62].