Immunopathogenesis and management of polymorphic light eruption

Tofacitinib: A Treatment Option for Recalcitrant Polymorphic Light Eruption and Its Mechanistic Rationale

Background: Polymorphous light eruption is largely characterized by a delayed-type (type IV) hypersensitivity reaction to 1 or more undefined endogenous ultraviolet-induced skin antigens. Objectives: To evaluate the efficacy of tofacitinib in refractory cases of polymorphous light eruption. Methods: Seven patients who had failed multiple systemic treatments or relapsed within 2 weeks of existing systemic agents with concomitant photoprotection were offered tofacitinib after written consent. Results: Initiation of tofacitinib led to a marked reduction of itching (mean ± SD 3.1 ± 1.12 days) followed by clinical resolution (mean ± SD 2.6 ± 1.1 weeks). The duration of therapy ranged from 1 to 3 months (mean ± SD 2 ± 0.63 months), and 4 of 7 patients had a recurrence in 5.5 weeks and were again initiated on tofacitinib with a prompt response. Conclusion: Tofacitinib inhibits Janus kinase (JAK)1 and JAK3 thus it can abrogate the effects of the predominant cytokine milieu of polymorphic light eruption (PMLE) and thus reduce the expression of aberrant inflammatory T lymphocyte expression in PMLE.

Eradication of skin microbiota restores cytokine production and release in polymorphic light eruption

Polymorphic light eruption (PLE) has been mechanistically linked to cytokine abnormalities. Emerging preclinical evidence posits the skin microbiome as a critical modulator of ultraviolet (UV)-induced cytokine expression, thereby influencing subsequent immune responses. This intricate relationship remains underexplored in the context of PLE. Hence, we investigated the differential responses between disinfected and non-disinfected skin following both single and repetitive exposures to solar-simulated UV radiation in patients with PLE. An experimental, half-body pilot study was conducted involving six PLE patients and 15 healthy controls. Participants' skin was exposed to single and multiple doses of solar-simulated UV radiation, both in disinfected and in non-disinfected skin areas. The co-primary outcomes were PLE score and cytokine expression in blister fluid analysed through OLINK proteomic profiling. Secondary outcomes were erythema, pigmentation, induction of apoptotic cells in vacuum-generated suction blisters, and density of infiltrate in skin biopsies of PLE patients. Among the 71 cytokines analysed, baseline expression levels of 20 specific cytokines-integral to processes such as apoptosis, inflammation, immune cell recruitment, cellular growth, and differentiation-were significantly impaired in PLE patients compared with healthy controls. Notably, skin disinfection reversed the observed cytokine imbalances following a single UV exposure at the minimal erythema dose (MED) level and exhibited even more pronounced effects after multiple UV exposures. However, no significant differences were evident in PLE score, erythema, pigmentation, or rates of apoptotic cell induction upon UV radiation. These findings provide evidence for UV-driven cytokine regulation by the skin microbiota and imply microbiome involvement in the PLE immune response.

Summer and spring elbow rashes is a variant of polymorphous light eruption: confirmation by photoprovocation and histopathology in a series of five cases

Background

Summer and spring eruptions on the elbows are a variant of polymorphous light eruption described on clinical and histopathological grounds; however, to our knowledge, they have not been confirmed by photobiological studies.

Objective

Based on photobiological studies, this study aimed to demonstrate the involvement of ultraviolet-A (UVA) radiation in this variant of polymorphous light eruption occurring exclusively on the elbows.

Methods

A series of five patients with polymorphous light eruption lesions on the elbows were included in our study. All patients underwent phototesting and photoprovocation of the skin lesions after exposure to a UVA light source [Philips UVA HPA lamp (400 W)]. All patients underwent punch biopsy and histopathological and immunohistochemical studies with anti-CD123.

Results

In all the cases, UVA irradiation caused the appearance of skin lesions on the elbows with characteristic polymorphous light eruption. Histological data showed edema in the superficial dermis and a perivascular lymphocytic infiltrate compatible with polymorphous light eruption. Immunohistochemical staining for CD1-23 showed negative results.

Conclusions

For the first time, photobiological photoprovocation studies demonstrated that repeated exposure to UVA radiation leads to the generation of skin lesions on the elbows, which are clinically and histologically consistent with summer and spring eruptions, confirming that elbow rash is a variant of polymorphous light eruption.

Clinical Applications of Polypodium leucotomos (Fernblock®): An Update

Exposure to sun radiation leads to higher risk of sunburn, pigmentation, immunosuppression, photoaging and skin cancer. In addition to ultraviolet radiation (UVR), recent research indicates that infrared radiation (IR) and visible light (VIS) can play an important role in the pathogenesis of some of these processes. Detrimental effects associated with sun exposure are well known, but new studies have shown that DNA damage continues to occur long after exposure to solar radiation has ended. Regarding photoprotection strategies, natural substances are emerging for topical and oral photoprotection. In this sense, Fernblock^®, a standardized aqueous extract of the fern Polypodium Leucotomos (PLE), has been widely administered both topically and orally with a strong safety profile. Thus, this extract has been used extensively in clinical practice, including as a complement to photodynamic therapy (PDT) for treating actinic keratoses (AKs) and field cancerization. It has also been used to treat skin diseases such as photodermatoses, photoaggravated inflammatory conditions and pigmentary disorders. This review examines the most recent developments in the clinical application of Fernblock^® and assesses how newly investigated action mechanisms may influence its clinical use.

Photodermatoses: what's new

PURPOSE OF REVIEW

The purpose of this review is to summarize and highlight the recent literature in photodermatoses. In the past year, there have been many developments in this heterogeneous group of conditions.

RECENT FINDINGS

This review is divided by photodermatoses type, which include idiopathic photodermatoses, photodermatoses secondary to exogenous agents, photodermatoses secondary to endogenous agents (the porphyrias), and genodermatoses. The idiopathic photodermatoses section focuses on case series and reports highlighting new disease presentations or further disease characterization and new treatment strategies for these disorders. The second section discusses a unique case and has a brief update on photoallergens. Clinical, diagnostic, and treatment updates for porphyrias are discussed in Section 3. For genodermatoses, we discuss complications and neoplastic risk of xeroderma pigmentosum and a few highlights from other rare disorders. Finally, we conclude with a brief overview of photoprotection updates, from assessing sun-damaged skin to the most effective photoprotective agents.

SUMMARY

Up-to-date information will help providers identify and manage this rare group of disorders.