Long-term survival and preservation of natural killer cell activity in a xeroderma pigmentosum patient with spontaneous regression and multiple deposits of malignant melanoma.

A 67-year-old man with xeroderma pigmentosum (XP) originally presented with malignant melanoma at the age of 28 years. This recurred 22 years later and subsequently numerous primary and secondary melanomas developed on the skin, several of which underwent spontaneous regression. Despite a marked lymphopenia, the proportion of natural killer cells was elevated and it is proposed that this led to the regression of the melanomas. Skin-derived fibroblasts from the patient were more sensitive to UVC (D10 approximately 3 J/m-2) than those from normal individuals (D10 approximately 15 J/m-2). The fibroblast culture was shown to be defective in excision repair with less than 10% of residual activity compared with controls. No assignment to a complementation group has yet been made. There was an elevated frequency of mutants resistant to 6-thioguanine in the circulating T lymphocytes.