Koolen-de Vries syndrome – National Case Series with clinical and molecular characterization

Introduction: Koolen-de Vries Syndrome (KdVS) is a rare genetic condition, caused by a 17q21.31 microdeletion, or a pathogenic variant in KANSL1 gene. The clinical picture includes developmental delay (DD)/intellectual disability (ID) with expressive language particularly impaired, dysmorphisms, neonatal hypotonia, and friendly behaviour. Aim: To characterize at the molecular and clinical levels all patients in Portugal diagnosed with KdVS.