ABSTRACT
Polymorphous light eruption (PLE) is a common, recurrent, acquired sunlight-induced disorder of delayed onset. The “polymorphous” designates the inter-individual variation in the clinical appearance of the disease. PLE, hydroa vacciniforme, and actinic prurigo belong to the group of so-called idiopathic photodermatoses. The term denotes skin diseases that occur in otherwise healthy individuals from exposure to natural or artificial light without the intervention of an exogenous photosensitizer. The Ultraviolet (UV)-induced immunosuppression is a consistent finding in normal skin and it was speculated that this process might protect the skin from UV-induced photoallergens. Thus, susceptibility of individuals to PLE could arise from a failure of normal UV-induced immunosuppression. The complex interrelationships between factors such as these have clearly contributed significantly to the conflicting nature of reports concerning the most effective wavelengths for PLE induction. Variation in the proportions of UVA and UVB present in terrestrial sunlight may also explain certain clinical characteristics of PLE.
