ERCC4 and xeroderma pigmentosum: Xeroderma pigmentosum (XP) is a group of multisystemic autosomal recessive conditions secondary to deficits in DNA repair systems.1-3 XP can result from variants in any of eight genes, thus defining eight complementation groups: XPA (XPA, OMIM number: 611153), XPB (ERCC3, OMIM number: 133510), XPC (XPC, OMIM number: 613208), XPD (ERCC2, OMIM number: 126340), XPE (DDB2, OMIM number: 600811), XPF (ERCC4, OMIM number 133520), XPG (ERCC5, OMIM number: 133530) and XP variant or XPV (POLH, OMIM number: 603968).