KANSL1 and Down syndrome: KANSL1 (KAT8 regulatory NSL complex, subunit 1) haploinsufficiency syndrome, also referred to as Koolen–De Vries syndrome (OMIM 610443), is characterized by highly typical facial features, including long and prominent philtrum, pear-shaped nose, everted lower lip and sparse eyebrows, mild-to-moderate intellectual disability, hypotonia and friendly behavior.