ZBTB24 and ICF syndrome: Pathogenic variants in four genes have been shown to cause ICF syndrome: DNMT3B (ICF1), ZBTB24 (ICF2), CDCA7 (ICF3), and HELLS (ICF4) (de Greef et al., 2011; Thijssen et al., 2015; Xu et al., 1999).