Xeroderma pigmentosum patients from Germany: Clinical symptoms and DNA repair characteristics

Abstract

Dermatologic, ophthalmologic, and neurologic examinations were carried out on 33 patients with clinical symptoms of xeroderma pigmentosum (XP). Complementation groups were determined for 23 patients. Types of tumors and complementation group were found to be related in the following way: In the XP variant groups basaliomas were the most frequently occurring malignant tumors, whereas in the D group pigmentary tumors, such as melanotic precanceroses and melanomas prevailed; in the A and the C group, spinaliomas seem to be the most frequent malignomas. The DNA repair activity was measured using colony-forming ability and unscheduled DNA synthesis. Colony-forming ability was quantitated as a function of 12 different UV doses and expressed in terms of D₀. Unscheduled DNA synthesis was determined autoradiographically by establishing dose-response curves, which analyzed by the characteristic value of linear regression. G₀, defined as the linear increase in the mean number of silver grains per nucleus when the UV dose is multiplied by the factor of e (i. e., 2.72), was derived from the slopes of the regression lines. The repair capability of XP fibroblast lines was classified on the basis of D₀ and G₀.