This syndrome is transmitted as a dominant x-linked trait, with incomplete penetrance 80% in males, 30% in females. It is caused by an amplification of the repeated CGG in the non-transcribed region towards 5' of the FMR1 gene promoter located at the FRAXA locus of the chromosome X, in Xq27,3.
Este síndrome se transmite como un rasgo dominante ligado al X con penetrancia incompleta 80% en hombres y 30% en mujeres y es causado por una amplificación del repetido CGG, en la región no transcrita hacia 5' del promotor del gen FMR1 ubicado en el locus FRAXA del cromosoma X, en Xq27,3.