XIST and Kabuki syndrome: The presence of the XIST gene on the ring chromosome is correlated with its inactivation while the absence of XIST region prevents the abnormal X chromosome from inactivation, leading to a functional disomy of regions of chromosome X associated with a more severe phenotype with mental retardation and facial features resembling those of the monogenic Kabuki syndrome (in particular the suggestive eversion of the lateral part of the lower lid was noted) [12–14].