Sir, Xeroderma pigmentosum (XP) and Cockayne syndrome (CS) are rare genodermatoses characterized by hypersensitivity to ultraviolet light. XP is a hereditary autosomal recessive condition, manifested clinically by abnormal photosensitivity of the skin and eyes, pigment anomalies, increased risk of cutaneous neoplasms and, frequently, by progressive neural degeneration (1 ± 3). CS is a rare auto...

Previous work has shown that in cells from the ultravioletsensitive genetic disorder, Cockayne's syndrome, DNA synthe sis fails to recover after ultraviolet irradiation, despite the fact that these cells have no detectable defect in either excision or daughter-strand repair pathways. We now show that Cockayne cells, as well as cells from a number of patients with xeroderma pigmentosum, are sens...

Previous work has shown that in cells from the ultravioletsensitive genetic disorder, Cockayne's syndrome, DNA synthe sis fails to recover after ultraviolet irradiation, despite the fact that these cells have no detectable defect in either excision or daughter-strand repair pathways. We now show that Cockayne cells, as well as cells from a number of patients with xeroderma pigmentosum, are sens...