The same year, at five years old, he was diagnosed with Koolen-de Vries syndrome due to heterozygous de novo mutation, c.611dupG, causing an amino acid change p.Met205TyrfsX9 variant in the lysine acetyltransferase 8 regulatory non-specific lethal complex subunit 1 (KANSL1) gene. The gene discussed is KANSL1; the disease is Koolen-de Vries syndrome.