Sensitivity to ultraviolet radiation in a dominantly inherited form of xeroderma pigmentosum

An Australian family is described in which a mild form of xeroderma pigmentosum (XP) is inherited as an autosomal dominant trait. Studies of lymphoblastoid cells and fibroblasts from affected persons demonstrated cellular sensitivity to ultraviolet (UV) light as judged by diminished clonogenicity and higher frequencies of UV induced chromosome aberrations compared to normal controls. After UV irradiation of dominant XP cells, replicative DNA synthesis was depressed to a greater extent than normal and the level of UV induced DNA repair synthesis was lower than that in normal cells. The level of sister chromatid exchanges and the numbers of 6-thioguanine resistant mutants induced by UV irradiation were equal to those found in normal controls. Although two subjects in the family had skin cancers, this dominant form of XP is not apparently associated with high risk, or large numbers, of skin cancers in affected persons.