The coexistence of photosensitive psoriasis with chronic actinic dermatitis

Desired response to phototherapy vs photoaggravation in psoriasis: what makes the difference?

Psoriasis commonly responds beneficially to UV radiation from natural sunlight or artificial sources. Therapeutic mechanisms include the proapoptotic and immunomodulating effects of UV, affecting many cells and involving a variety of pro- and anti-inflammatory cytokines, downregulating the Th17/IL-23 response with simultaneous induction of regulatory immune cells. However, exposure to UV radiation in a subset of psoriasis patients leads to exacerbation of the disease. We herein shed light on the predisposing factors of photosensitive psoriasis, including genetics (such as HLA-Cw*0602 or CARD14), gender and coexisting photodermatoses such as polymorphic light eruption (PLE) in the context of potential molecular mechanisms behind therapeutic photoresponsiveness or photoaggravation. UV-induced damage/pathogen-associated molecular patterns, damage to self-coding RNA (signalling through Toll-like receptors), certain antimicrobial peptides and/or inflammasome activation may induce innate immunity, leading to psoriasis at the site of UV exposure when there is concomitant, predisposing resistance against UV-induced suppression of the adaptive immune response (like in PLE) that otherwise would act to reduce psoriasis.

Psoriasis of the face and flexures

Facial and flexural psoriasis may impair the quality of life of psoriatic patients considerably. For the adequate management of psoriasis it is important to pay attention to lesions at these sensitive sites, which require an approach different to that for lesions on other sites in several respects. An extensive literature search was carried out to collect evidence-based data on facial and flexural psoriasis with respect to epidemiology, clinical aspects, pathogenetic factors and various treatments. Subsequently, a panel of experts, the Copenhagen Psoriasis Working Group (CPWG), discussed these aspects and several recommendations were formulated reconciling the evidence-based data. Facial psoriasis occurs in 17-46% of psoriatics and flexural psoriasis is experienced by 6.8-36% of patients with psoriasis. Therefore, psoriasis at these sites cannot be regarded as a rare manifestation. Facial psoriasis is a prognostic marker indicating a poor prognosis of psoriasis. Facial and flexural psoriasis cannot be regarded as distinct disease entities but rather as site variations. The clinical features of facial psoriasis suggest that there are three subtypes: hairline psoriasis, sebo-psoriasis and true facial psoriasis. Otitis externa and ocular manifestations should not be neglected. Evidence that microbiological factors may be relevant to facial and flexural psoriasis is virtually absent. For facial psoriasis the response to UV radiation is variable. At least 5% of psoriatics have photosensitive psoriasis. In these patients photosensitive diseases such as lupus erythematodes and polymorphic light eruption have to be excluded. Based on the literature assessment and working group discussions the CPWG concluded the following. (1) Low-potency topical corticosteroids, vitamin D3 analogues and calcineurin inhibitors are first choice treatments in facial and flexural psoriasis. Evidence for the efficacy of the first two modalities is at level 3 while it is at level 1 for the third one. An individualized approach is indicated; for example, in case of corticosteroid side effects in the past the other two modalities should be selected and in unstable psoriasis prone to irritation, monotherapy with vitamin D3 analogues should be avoided. (2) Antimicrobial treatments are not indicated for facial and flexural psoriasis. (3) Dithranol and tar treatment are not indicated as first-line treatment but only if the first-line options fail. (4) In case topical therapies are not effective, phototherapy and systemic treatments are indicated. (5) For future drug development the combination of vitamin D3 analogues with low strength corticosteroids is recommended.