ERCC1 and COFS syndrome: A limited number of patients with mutations in ERCC4/XPF display late-onset neurological symptoms with or without skin cancers (29, 30), although only exceptional cases with rare variants show early onset devastating symptoms observed in CS, FA, XPCSFA, cerebro-oculo-facio-skeletal syndrome (COFS), and XFE progeroid syndrome, because the ERCC1-XPF endonuclease is essential for development (15, 31, , , –35).