The same applies for mutations in the down-stream NER factors XPB, XPD, XPF, ERCC1 and XPG that cause combined XP/CS, or severe developmental/degenerative multisystem disorders such as COFS and XFE that share multiple features with severe CS forms [35], [48]–[51]. The gene discussed is ERCC5; the disease is xeroderma pigmentosum.