Environmental factors, such as skin exposure to ultraviolet (UV) radiation from sunlight and other sources [3], and genetic factors, including inherited mutations in cyclin-dependent kinase inhibitor 2A (CDKN2A), cyclin-dependent kinase 4 (CDK4), xeroderma pigmentosum (XP), and melanocortin 1 receptor (MC1R) [2,4], are frequently identified as factors related to CM. The gene discussed is CDK4; the disease is xeroderma pigmentosum.