More recently, <i>SMC1A</i> truncating variants have been described as the cause of a neurodevelopmental disorder with early-childhood onset drug-resistant epilepsy with seizures that occur in clusters, similar to that seen in <i>PCDH19</i>-related epilepsy, but without the classical features of CdLS. This evidence concerns the gene PCDH19 and Cornelia de Lange syndrome.