Etiology of hydroa vacciniforme is not known. Skin lesions occur on sun-exposed skin, such as the face, ears, and hands, and may be accompanied by a mild keratoconjunctivitis, photophobia, and constitutional symptoms. In Scotland, for example, the reported prevalence is 0.34 cases per 100,000 people. No mortality is associated with typical hydroa vacciniforme. Females have a higher incidence of HV than males and report earlier onset.
Affected males have a longer course of disease.
Cases of HV in infants and the elderly also have been described. Imaging studies are not routinely ordered as part of the work-up of hydroa vacciniforme. Early lesions reveal an epidermal, multilocular vesicle with reticular degeneration. A dense, perivascular, lymphohistiocytic infiltrate with vessel hemorrhage and thrombosis may occur in the dermis. Late lesions show epidermal and dermal necrosis with a surrounding, chronic, inflammatory infiltrate.