SMC1A and Cornelia de Lange syndrome: The three genes recognized to cause CdLS include the NIPBL gene on chromosome 5 (approximately 50% of CdLS patients carry this gene mutation) [15, 16], SMC1A gene on chromosome X (approximately 5% of CdLS patients) [17], SMC3 gene on chromosome 10 (there has been only 1 case report of this gene mutation) [18], and RAD21 and HDAC8 mutations as well [19].