Xeroderma pigmentosum complementation group F: Report of a case and review of Japanese patients

Xeroderma pigmentosum (XP) is an autosomal recessive genetic disorder characterized by extraordinary sensitivity to sunlight, resulting in cutaneous malignant tumors. Among XP, XP‐F presents relatively uniquely in Japanese. To clarify the characteristics of this group, we describe a case of XP‐F and review Japanese cases previously reported. A 50‐year‐old Japanese woman was referred to us with multiple, variously sized, light‐ or dark‐brown macules on the face and sunlight‐exposed extremities. She had experienced bulla formation with approximately 10 min of sunlight exposure during her elementary school years. Her parents had been first cousins, and her mother and sister had photosensitivity. She showed no neurological or developmental abnormalities. Ultraviolet (UV) irradiation testing revealed normal levels for minimal erythema dose with UV‐A and UV‐B. Sensitivity to UV‐C and DNA repair ability in the patient's fibroblasts were indicated between that in normal individuals and that in an XP‐A patient. Complementation assay revealed that transfection of the XPF gene led most efficient DNA repair compared with the other XP genes. Therefore, the patient was diagnosed with XP‐F. Twenty‐three cases of Japanese patients (six males, 17 females) with XP‐F have been reported, including the present case. Our review suggested a relatively high prevalence of 50% (11/22) for cutaneous malignant tumors. A significant difference was evident in the mean age at first medical consultation between patients with cutaneous malignant tumors (53.6 years) and patients without such tumors (30.8 years). This suggests that cutaneous malignant tumors could occur in the age range of 30–50 years in XP‐F patients.