Cockayne syndrome in two adult siblings.

Although survival beyond the second decade is unusual in patients who have Cockayne syndrome, we describe two brothers with the syndrome who are 42 and 55 years of age. Their cultured skin fibroblasts showed extreme UV sensitivity but had almost normal UV-induced unscheduled DNA synthesis. The patients were classified as genetic complementation group B after study of the recovery of RNA synthesis after UV irradiation of fused cells. Clinical phototesting revealed a reduced threshold for UVB erythema.