Photosensitivity disorders of the skin are conditions in which an abnormal cutaneous response occurs after exposure to ultraviolet radiation or visible light. The major categories of photosensitivity disorders are idiopathic photodermatoses, photodermatoses due to exogenous or endogenous agents, photoexacerbated dermatoses, and photosensitive genodermatoses, and will be reviewed here (table 1).
An overview of photosensitivity, including photobiology, patient evaluation, and photoprotection, is discussed separately. Polymorphous light eruption, which is a type of idiopathic photodermatosis, is also discussed separately. (See "Overview of cutaneous photosensitivity: Photobiology, patient evaluation, and photoprotection" and "Polymorphous light eruption".)
THE IDIOPATHIC PHOTODERMATOSES
The idiopathic photodermatoses are a group of photosensitivity disorders whose pathogenesis remains unclear. Many of these disorders have features suggesting that they are immunologically mediated.
The idiopathic photodermatoses include polymorphous light eruption, actinic prurigo, hydroa vacciniforme, chronic actinic dermatitis, and solar urticaria (table 1).
Polymorphous light eruption — Polymorphous light eruption (PMLE) is the most common idiopathic photodermatosis and is sometimes colloquially called "sun poisoning" or “sun allergy.” PMLE and juvenile spring eruption, a PMLE variant, are reviewed separately. (See "Polymorphous light eruption".)