RAD23B and xeroderma pigmentosum: Additionally, sagging was also associated with the “nucleotide excision repair” pathway, pointing out several genes, namely DDB1 and RAD23B, which are both involved in XP (Kapetanaki et al., 2006; Petruseva et al., 2009), and ERCC8 associated with the Cokayne syndrome (Ridley et al., 2005), another disease characterized by sun hypersensitivity and progeroid appearance, but without an association with skin cancer.