Although patients with mild symptoms of atypical Cockayne syndrome (CS) have been described, there has not been a report of a patient with CS whose only clinical manifestation was cutaneous photosensitivity. Cells from patients with CS show UV sensitivity, reduced recovery of RNA synthesis, but normal UV-induced unscheduled DNA synthesis. On the other hand, the patients with UV-sensitive syndrome have only cutaneous photosensitivity and skin freckles, whereas those cells respond to UV radiation in a similar fashion to the CS cells. We describe a patient with CS who showed only photosensitivity without typical clinical manifestations of CS, but his cells showed UV sensitivity, reduced recovery of RNA synthesis, and normal unscheduled DNA synthesis after UV radiation similar to CS cells. Furthermore, the patient was assigned to complementation group B of CS on the basis of the results of complementation analysis. The present report suggests that CS has a wider spectrum than that considered previously. (J Am Acad Dermatol 1998;39:565-70.)