Epidemiological Study of Xeroderma Pigmentosum in Japan: Genotype-Phenotype Relationship

Abstract

Xeroderma pigmentosum (XP) is a rare autosomal recessive hereditary disease caused by the deficiency of repairing DNA damage caused by ultraviolet radiation and some other compounds. Patients with XP display pigmentary change and numerous skin cancers in sun-exposed body sites, and some patients show exaggerated severe sunburn upon minimum sun exposure and neurological symptoms. We have conducted the nationwide survey for XP since 1980 as a research project supported for the intractable disease initiated by the Japanese Ministry of Health, Labour and Welfare. The frequency of each complementation group in Japan is considerably different from that in Western countries; in Japan, XP complementation group A is the most frequent, followed by variant type. Regarding skin cancers in XP, basal cell carcinoma was the most frequent cancer that patients with XP developed, followed by squamous cell carcinoma and malignant melanoma. The frequency of these skin cancers in patients with XP-A has decreased in these 20 years, and ages of onset of developing skin cancers are much older than those previously observed, which is greatly attributed to the education of sun protection for the patients with XP and their parents and guardians for these 20 years. In order to encourage the patients and their parents to perform appropriate sun protection for the prevention from skin cancers, definite diagnosis but not possible diagnosis is crucial. In addition, diagnosing at younger ages is important. On the other hand, the effective therapy for neurologic XP has not been established yet, and this needs to be done urgently.