AbstractA case of xeroderma pigmentosum group D in a 36‐year‐old woman (XP85TO) is reported. The patient had severe photosensitivity from age 4, and developed multiple basal cell epitheliomas and solar keratoses but exhibited no apparent neurological defects. A skin phototest by monochromatic ultraviolet light revealed a delayed peak of erythema 48 h after irradiation and lowered minimal erythemal doses. Unscheduled DNA synthesis induced in XP85TO cells was 36.0% in dermal fibroblasts and 32.6% in epidermal keratinocytes compared with normal cells. The XP85TO cells were sensitive to ultraviolet killing (n=1.0, D0=0.80J/m2). In complementation analysis, XP85TO cells did not complement with xeroderma pigmentosum group D cells. These results indicate that patient XP85TO had xeroderma pigmentosum group D.The Japanese group D patients including XP85TO case showed delayed onset of skin malignant tumors and neurological abnormalities, compared with the group D patients in Europe and the United States. These findings suggest a possible ethnic variation of the clinical phenotype, despite the similar repair defect and ultraviolet hypersensitiv