Mutations in five genes belonging to the cohesin pathway, namely SMC1A, SMC3, RAD21, NIPBL and HDAC8, have been identified in Cornelia de Lange syndrome (CdLS, OMIM 122470, 300590, 610759, 300882 and 614701) patients23, 24, 25, 26, 27, 28, a rare developmental disorder characterized by typical facial features, cognitive impairment, growth delay and birth defects including upper extremity anomalies, with a broad variability in phenotypic expression29. Here, SMC3 is linked to Cornelia de Lange syndrome.