UV-induced mutations and skin cancer: how important is the link?

Studies with patients having the inherited DNA repair disorders xeroderma pigmentosum (XP), Cockayne syndrome (CS), and sun-sensitive trichothiodystrophy (TTD) have shown that neither the defect in repair nor the consequent elevated frequency of sunlight-induced mutations in the skin is sufficient to account for the classically high incidence of skin cancer in XP patients. The possible ways in which different mutations in the XP(D) gene and deficiencies in the immune system may be involved are discussed.