Xeroderma pigmentosum (XP) is characterized by sun sensitivity, ocular involvement, and greater than 1000-fold increased risk of cutaneous and ocular neoplasms. About 30% of affected individuals have neurologic manifestations, including acquired microcephaly and cognitive impairment. Multiple genes are associated with XP including XPA, ERCC3 (XPB), XPC, ERCC2 (XPD), DDB2 (XPE), ERCC4 (XPF), ERCC5 (XPG), and POLH (XP-V). XP is inherited in an autosomal recessive manner.