Beckwith–Wiedemann syndrome (BWS, OMIM no. 130650) is an overgrowth condition caused by epigenetic or genetic alterations in the imprinted H19/IGF2-KCNQ1/CDKN1C locus, spanning nearly 1 Mb in 11p15.5.1 The two major causes of BWS are increased IGF2 expression or decreased CDKN1C expression. Here, KCNQ1 is linked to Beckwith-Wiedemann syndrome.