CDKN1C and IMAGe syndrome: IMAGe syndrome is usually caused by heterozygous missense variants in the key negative cell cycle regulator, cyclin‐dependent kinase inhibitor 1C (CDKN1C).41 These changes are localized to the PCNA‐binding domain and cause a gain‐of‐function and growth repression (Figure 2A).41, 42, 43, 44 The mechanism is unclear but may involve decreased degradation of CDKN1C, allowing prolonged cell cycle repression and delayed S‐phase progression.