Cultured skin fibroblasts derived from three patients with disseminated superficial actinic porokeratosis (DSAP) are hypersensitive to the lethal effects of X-radiation but not to those of ultraviolet (UV) light.

Disseminated superficial actinic porokeratosis (DSAP), skin lesions of which are known to be induced by ultraviolet (UV) light, does not develop into skin cancer as frequently as other types of porokeratosis (PK). To establish the cellular basis of this characteristic of DSAP, we examined the colony-forming ability of UVC light- or X-ray-irradiated cultured fibroblasts derived from DSAP patients' skin. Sensitivity to the lethal effects of UV light was not significantly different between 3 DSAP and 5 control cell strains. In contrast, DSAP cell strains were significantly hypersensitive to the lethal effects of X-radiation, although the sensitivity was less than that of cell strains from other types of PK patients. The results indicate that the actinic character of DSAP is not reflected in the cellular response to the lethal effects of UV light, but suggest that DSAP shares X-ray sensitivity, which is probably associated with the cancer-prone nature of PK.