Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by an expansion of the CGG trinucleotide repeats (more than 200, termed full mutation, FM) in the 5′ untranslated region of the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene on the Xq27.3 chromosome region [1,2]. The gene discussed is FMR1; the disease is fragile X syndrome.