<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A rare genetic syndrome caused by mutations in the NSD1 gene. It is characterized by excessive physical growth early in life, mild mental retardation, and delayed cognitive and social development. Children affected by this syndrome are tall with larger than normal heads.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>