Loss-of-function mutations of p57Kip2 have been identified in BWS patients [44], and gain-of-function mutations in the Proliferating cell nuclear antigen (PCNA)-binding domain of p57Kip2 have been identified in growth retardation syndromes such as SRS and IMAGe syndrome [46–48]. The gene discussed is CDKN1C; the disease is Beckwith-Wiedemann syndrome.