Xeroderma pigmentosum and pigmented xerodermoid.

Xeroderma pigmentosum (XP) is a rare hereditary disease in which the skin is extremely sensitive to sunlight. After a slight exposure to sunlight the skin develops widespread poikiloderma including multiple hyperplasia and malignancies of epidermal and dermal origin. We could confirm Cleaver's results in finding dark repair replication very much reduced, not only in cultured fibroblasts, but also in epidermal cells and lymphocytes. Our investigation is based on three solitary cases of autosomal recessive inheritance. Working in this field, we found a condition similar to XP induced by excessive sun exposure of the skin over decades with manifestations after 30 years of age. We therefore term it "pigmented xerodermoid". Repair replication in epidermal cells seems to be normal. In our two cases we found a strong and almost total depression of DNA synthesis after application of low doses of UV light, while in normal skin the premitotic DNA synthesis is only reduced to a degree which is a function of irradiated energy.