Actinic prurigo is a photodermatosis that involves the skin, lips, and conjunctival mucosa mainly found in native and admixed populations of Latin America. Usually, it is diagnosed during childhood following extended solar exposure. It has a chronic course where pruriginous papules, nodules, and excoriated plaques on photoexposed skin areas are clearly evident. This morphology usually is accompanied by ocular pseudopterygium and cheilitis.
There is a lack of knowledge regarding its pathophysiology, but current histological and research findings suggest that it is an ongoing type IV hypersensitivity reaction with still unknown other immunopathogenic processes. They include the involvement of HLA-DR4 genes and the infiltration of CD4 lymphocytes, eosinophils, mast cells, and a serum increase of IgE.
Clinical manifestations are usually sufficient to diagnose this condition; however, phototesting can help diagnose undetermined or less severe cases. Although the presence of lymphoid follicles in the mucosa is not a frequent finding, its presence highly suggests a diagnosis of actinic prurigo.
Treatment includes intensive photoprotection, anti-inflammatories, and immunomodulators.