These include Cornelia de Lange Syndrome (CdLS, caused by mutations in NIPBL, Smc1A, Smc3, Rad21 or HDAC8 (refs 2, 3, 4, 5)), Roberts Syndrome (RBS, caused by ESCO2 mutations6, 7) and Warsaw Breakage Syndrome (WABS, caused by DDX11 mutations8). The gene discussed is ESCO2; the disease is Warsaw breakage syndrome.