Disseminated superficial actinic porokeratosis: experimental induction and exacerbation of skin lesions.

A 55-year-old woman with disseminated superficial actinic porokeratosis (DSAP) had lesions on sun-exposed skin areas that were exacerbated during the summer months and involuted in winter. This is the third report in which induction and exacerbation of DSAP lesions were achieved by irradiation with artificial ultraviolet light sources. Our data show that UVB plus UVA is more effective in inducing new or exacerbating preexisting skin lesions than either wavelength alone. We believe that testing with the appropriate ultraviolet light sources is a practical means to differentiate between DSAP and disseminated superficial porokeratosis.