[Actinic prurigo].

Actinic prurigo is a rare idiopathic photodermatosis, which shares some features with atopic dermatitis, polymorphous light eruption, hydroa vacciniforme and persistent light reaction. It is, however, recognized as a distinct entity. Among American Indians a familial variant is observed. Characteristic features are a chronic course with sustained exacerbations, which are seasonal at first, but later perennial. The disorder may improve in adulthood. The typical clinical features are urticarial plaques a few hours after UV exposure, and a persistent eczematous, prurigo-like rash distributed over skin areas exposed to light but sometimes extending even into photoprotected areas. Therapy is extremely difficult and unrewarding. In the present paper the entity is defined and three typical cases are presented.