New Form of Molecular Defect in Xeroderma Pigmentosum

Abstract

XERODERMA pigmentosum is a rare hereditary disease of the human skin. After slight exposure to sunlight the skin develops widespread poikiloderma with spotted dyschromia, telangiectasia and atrophy of the epidermis including multiple hyperplasia and the following malignancies of epidermal and dermal origin: basal cell and squamous cell carcinoma, melanoma, fibroma, sarcoma, histiocytoma, neurofibroma and angioma^1,2. The molecular basis of light sensitivity and accelerated light induced carcinogenesis of xeroderma pigmentosum may involve a decreased tolerance of individual cells to light³. The initial direct damage is not increased, but the ability of cells to tolerate light induced DNA damage is decreased: investigation of cultured fibroblasts of xeroderma pigmentosum patients showed that these cells are unable to repair ultraviolet-induced single-strand DNA lesions³. The molecular defect lies in the initial stage of the repair process, probably at the endonuclease level^4,5.