POLH and xeroderma pigmentosum: To date, eight genes have been identified to be associated with autosomal recessive XP (Fassihi et al., 2016), including XPA (Salob, Webb, & Atherton, 1992), ERCC3 (XPB) (Lehmann, 1982), XPC (Li, Bales, Peterson, & Legerski, 1993), ERCC2 (XPD) (Frederick, Amirkhan, Schultz, & Friedberg, 1994) DDB2 (XPE) (Nichols, Ong & Linn, 1996), ERCC4 (XPF) (Fujiwara et al., 1985), ERCC5 (XPG) (Keijzer et al., 1979), and POLH (XPV) (Masutani et al., 1999).