Xeroderma Pigmentosum

Abstract

Xeroderma pigmentosum is a hereditary disease clinically manifested primarily on sun-exposed skin, which develops abnormal pigmentation and malignant tumors. Mental retardation, areflexia, and other neurological abnormalities are seen in some patients. Only one biochemical defect has been found: cells from various tissues repair ultraviolet-induced deoxyribonucleic acid (DNA) damage slowly, compared with normal cells. Cell fusion studies show that genetic complementation can occur between fibroblasts from certain pairs of patients, thus overcoming the DNA-repair defect in each member of the pair and demonstrating the heterogeneity of the genetic lesion. The patients at NIH who have slow DNA repair comprise four distinct complementation groups, indicating that at least four mutations can cause defective DNA repair.