Recently, the role played by the Y chromosome in sexual development has been recognized in brain development too; the two X–Y homologous gene pair, PCDH11X/Y and NLGN4X/Y, are emerging as two important families of genes, protocadherins and neuroligins, involved in neurodevelopmental disorders (schizophrenia, autism, intellectual disability, and epilepsy) although the clinical evidence is still rare [3]. The gene discussed is PCDH11X; the disease is Intellectual disability.