<h4>Background</h4>Hackman-Di Donato syndrome (Online Mendelian Inheritance in Man no. 301,039), caused by mutations of the NKAP gene, located in Xq24, is a rare genetic disorder characterized by a Marfanoid phenotype, intellectual disability, and abnormalities of the musculoskeletal system. This evidence concerns the gene NKAP and Intellectual disability.