[Cockayne Syndrome].

Cockayne syndrome (CS) is an autosomal recessive disorder characterized by severe photosensitive genodermatosis that is associated with premature aging caused by defects in the UV-induced DNA damage repair system, particularly the transcription-coupled nucleotide excision repair. The clinical features of CS include photosensitivity, a characteristic senile face, significant developmental abnormalities, such as short stature, underweight, and microcephaly, progressive cachexia, severe visual impairment, and sensorineural deafness. CS is clinically classified into type I (classical type), type II (congenital or severe type) and type III (late-onset or adult-onset type). Additionally, there exists a rare form of xerodema pigmentosum-Cockayne syndrome (XP/CS) complex. The incidence of CS is 2.7 in 1,000,000 individuals in Japan and 90% of the cases are type I. Unlike XP, in CS, skin cancer is not known to occur in areas of skin exposed to sunlight. However, we observed a case where solar keratosis developed in adult-onset CS patients (CS type III) with a pathological mutation in the CSB gene. In XP/CS, patients easily develop skin cancer from early childhood in areas of the skin exposed to sunlight.