Polymorphous Light Eruption Differential Diagnoses

Updated: Jan 22, 2020
  • Author: Saud A Alobaida, MBBS, FRCPC; Chief Editor: Dirk M Elston, MD  more...
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DDx

Diagnostic Considerations

Some physicians regard actinic prurigo (AP) as a distinct photodermatosis, and other physicians consider it an insidiously developing, markedly excoriated variant of polymorphous light eruption (PMLE). AP is characterized by a high incidence of atopy and familial predisposition. It is likely to involve covered skin.

Chronic actinic dermatitis is a term that encompasses several syndromes previously considered separate entities (ie, actinic reticuloid, persistent light reactivity, photosensitive eczema, photosensitivity dermatitis)’ however, now they are considered variants of the same condition. Clinically, lesions are usually more eczematous and infiltrated than in PMLE and involve mostly exposed skin, but they may generalize to erythroderma. The actinic reticuloid form of chronic actinic dermatitis has a histologic pattern that resembles cutaneous lymphoma, with CD8+ cells predominating. The minimal erythema dose (MED) to UVB, and sometimes UVA, is reduced.

Solar urticaria represents an immediate hypersensitivity response to UV radiation. Characteristic whealing may be accompanied by systemic symptoms of faintness, nausea, and bronchospasm.

A novel condition resembling PMLE and effecting the face and body has been reported under the name “prolonged exposure dermatosis.” It has clinical and histologic findings similar to PMLE, and it has been reported to occur during a winter wilderness expedition. [41] Its clinical basis needs more explication.

A 2010 study by Gronhagen et al reported on the importance of differentiating systemic lupus and cutaneous lupus erythematosus from PMLE. [42] In this study, 23% of 260 systemic lupus erythematosus patients had cutaneous lupus erythematosus, and a history of PMLE was found in 42%. The history of PMLE can proceed the typical eruption of cutaneous lupus erythematosus.

Differential Diagnoses