The KANSL1 haploinsufficiency syndrome, also referred to as Koolen De Vries syndrome (KdVS, MIM 610443) is a multisystem disorder characterized by intellectual disability (ID), hypotonia, distinct facial traits, including long face, upslanting palpebral fissures, sparse eyebrows, long and prominent nose with bulbous nasal tip, long philtrum and everted lower lip. This evidence concerns the gene KANSL1 and Koolen-de Vries syndrome.