ERCC4 and Down syndrome: Prime examples are Cockayne syndrome (CS; affected proteins: CSB, CSA), XPF-ERCC1 syndrome (XFE; affected proteins: XPF, ERCC1) or trichothiodystrophy (TTD; affected proteins: XPB, XPD, TTDA) that are caused by defects in the transcription-coupled subpathway of nucleotide excision repair (TC-NER) [6],[7].