FMR1 and fragile X syndrome: An expansion of the CGG repeat in 5′UTR region of the FMR1 gene may cause three different clinical conditions: fragile X syndrome (number of CGG repeats over 200), fragile X-associated primary ovarian insufficiency (FXPOI) and fragile X-associated tremor/ataxia syndrome (FXTAS; in both number of CGG repeats within range 55–200).