Gain-of-function mutations affecting the highly conserved 279th amino acid within analogous proliferating cell nuclear antigen (PCNA) domains of the CDKN1C gene have been reported in IMAGe syndrome and familial SRS (p.Arg279Pro, p.Arg279Ser, p.Arg279Leu) (15). Here, CDKN1C is linked to Silver-Russell syndrome.