Cornelia de Lange syndrome (CdLS) is an autosomal dominant or X-linked rare genetic disorder caused by mutations in one among at least seven different genes: NIPBL, SMC1A, SMC3, RAD21, HDAC8, BRD4 and ANKRD11 (CdLS1, OMIM #122470; CdLS2, #300590; CdLS3, #610759; CdLS4, #614701; CdLS5, #300882 CdLS6, #620568; *611192). The gene discussed is RAD21; the disease is Cornelia de Lange syndrome.