Classification and evaluation of photodermatoses

Photodermatoses can be classified into five general categories: 1) idiopathic photodermatoses, including polymorphic light eruption (PMLE), actinic prurigo, hyroa vacciniforme, chronic actinic dermatitis, and solar urticaria; 2) photodermatoses which are secondary to exogenous agents, including phototoxic and photoallergic reactions; 3) photodermatoses secondary to endogenous agents, mainly the porphyrias; 4) photoexacerbated dermatoses, including autoimmune disease, infectious conditions, and nutritional deficiencies; and 5) genodermatoses. The initial step in evaluating a photosensitive patient is based on a directed personal and family history. The morphology of the eruption, phototests, and in some patients, photopatch tests are essential in focusing the diagnosis. Skin biopsies and laboratory investigations, such as antinuclear antibody (ANA) panels and porphyrin profiles, may be required to further confirm the diagnosis.