Hydroa vacciniforme. Diagnosis by repetitive ultraviolet-A phototesting.

Hydroa vacciniforme is a rare disorder manifested in early childhood by recurrent photoinduced vesicles that heal with scarring. We report a case in which repetitive exposures to artificial ultraviolet light in the A range reproduced the clinical findings induced by natural sunlight. Phototesting may be viewed as an important diagnostic aid, as the induction of lesions clinically identical to hydroa vacciniforme can provide a reliable criterion for the diagnosis.