Pathogenesis of solar urticaria: Classic perspectives and emerging concepts

Successful serial plasmapheresis for solar urticaria, a case report and literature review

BACKGROUND/PURPOSE

Amidst the emergence of new therapeutic options, traditional therapeutic plasmapheresis (TPE) used in diseases involving a toxic substance in the plasma, remains a viable alternative for cases of recalcitrant solar urticaria (SU). We emphasize the importance of documenting successful experience with repeated plasmapheresis to increase awareness amongst physicians and dermatologists regarding this effective treatment option.

MATERIAL AND METHOD

We reported a case of recalcitrant SU that had not responded to a combination of H1-antihistamines, immunosuppressants, omalizumab and intravenous immunoglobulin. We introduced serial TPE, which involved two consecutive days of procedures for each course was introduced. We detailed the regimen and highlighted the clinical and objective benefits observed with multiple treatments. Additionally, we compared this to other plasmapheresis regimens and their treatment responses previously reported for solar urticaria.

RESULTS

Our patient underwent serial TPE, totaling 42 procedures over five years. Following the last TPE session, phototesting showed a sustained prolongation of minimal urticating doses (MUDS), which exceeded the maximum tested doses across nearly all ultraviolet (UV) and visible light ranges, with the exception of the two short ultraviolet B (UVB) wavelengths. MUDs increased to 25 from 6 mj/cm2 at 307.5± 5nm, and to 500 from 15 mj/cm2 at 320 ± 10nm, before the initial TPE. In our review, we included five articles covering eight SU patients who received TPE. Of these, the five patients with positive intradermal tests responded particularly well immediately after treatment. However, the condition relapsed within two weeks in one patient and within two months in another. In contrast, the other three patients with negative intradermal tests, showed no significant benefits from the treatment. No serious side effects from TPE were reported amongst the patients.

CONCLUSIONS

This review underscores the efficacy of serial plasmapheresis procedures in treating refractory cases of SU, high3lighting the robust results observed.

Chronic Inducible Urticaria

Chronic inducible urticaria (CIndU) is characterized by the appearance of hives (urticaria) and/or angioedema in response to specific triggers or stimuli. For accurate diagnosis, anamnesis-driven specific, and if available, standardized trigger testings, as well as patient reported outcomes, should be applied. The currently recommended treatment algorithm is the same as for chronic spontaneous urticaria but is largely off-label for CIndU. New, and possibly more disease-specific, treatment options are needed for CIndU patients, who are often severely impacted by their disease. Several clinical trials are currently ongoing.

New insights into chronic inducible urticaria

PURPOSE OF REVIEW

Chronic inducible urticaria (CIndU) is a group of long-persisting and challenging to manage diseases, characterized by recurrent wheals and angioedema induced by definite triggers. In this review, we address recent findings on CIndU pathogenesis, diagnosis as well as its treatment, and we discuss novel potential targets that may lead to the development of more effective therapies for CIndU patients.

RECENT ADVANCES

Meaningful advances in the understanding of its pathogenesis have been reported in the last decades. Novel CIndU-specific patient-reported outcome measures enable a closer and better evaluation of patients. CIndU is a hard-to-treat disease that highly impairs quality of life (QoL) of affected patients. Provocation tests allow to diagnose CIndU subtypes. The only licensed and recommended treatment for CIndU are second generation non-sedating H1-antihistamines, which lack efficacy in many cases. Omalizumab off-label use has been assessed in all types of CIndU with overall good outcomes. Promising emerging therapies currently assessed in chronic spontaneous urticaria are paving the path for novel treatments for CIndU.

'Omalizumab changed my life': a patient perspective on solar urticaria

This patient perspective on solar urticaria demonstrates some of the key clinical characteristics and impact of solar urticaria, as well as a first-hand account of the transformative potential of omalizumab therapy. The clinicians’ comment reviews clinical features and aspects of diagnosis and management.

[Solar urticaria and polymorphous light eruption]

Solar urticaria is a rare idiopathic photodermatosis. According to the current knowledge its pathogenesis is most likely based on an allergic type I reaction to an autoantigen activated by ultraviolet (UV) radiation or visible light. As many of the patients suffer from severe forms of the disease, it may therefore severely impair the quality of life of those affected. In contrast, polymorphous light eruption is a very common disease, which, according to the current data, can be interpreted as a type IV allergic reaction to a photoallergen induced by UV radiation. As the skin lesions heal despite continued sun exposure, the patients' quality of life is generally not significantly impaired. These two clinically and pathogenetically very different light dermatoses have shared diagnostics by means of light provocation and an important therapeutic option (light hardening). Herein, we present an overview of the clinical picture, pathogenesis, diagnosis and available treatment options for the above-mentioned diseases.

Solar urticaria involves rapid mast cell STAT3 activation and neutrophil recruitment, with FcεRI as an upstream regulator

BACKGROUND

Solar urticaria is a rare photodermatosis characterized by rapid-onset sunlight-induced urticaria, but its pathophysiology is not well understood.

OBJECTIVE

We sought to define cutaneous cellular and molecular events in the evolution of solar urticaria following its initiation by solar-simulated UV radiation (SSR) and compare with healthy controls (HC).

METHODS

Cutaneous biopsy specimens were taken from unexposed skin and skin exposed to a single low (physiologic) dose of SSR at 30 minutes, 3 hours, and 24 hours after exposure in 6 patients with solar urticaria and 6 HC. Biopsy specimens were assessed by immunohistochemistry and bulk RNA-sequencing analysis.

RESULTS

In solar urticaria specimens, there was enrichment of several innate immune pathways, with striking early involvement of neutrophils, which was not observed in HC. Multiple proinflammatory cytokine and chemokine genes were upregulated (including IL20, IL6, and CXCL8) or identified as upstream regulators (including TNF, IL-1β, and IFN-γ). IgE and FcεRI were identified as upstream regulators, and phosphorylated signal transducer and activator of transcription 3 expression in mast cells was increased in solar urticaria at 30 minutes and 3 hours after SSR exposure, suggesting a mechanism of mast cell activation. Clinical resolution of solar urticaria by 24 hours mirrored resolution of inflammatory gene signature profiles. Comparison with available datasets of chronic spontaneous urticaria showed transcriptomic similarities relating to immune activation, but several transcripts were identified solely in solar urticaria, including CXCL8 and CSF2/3.

CONCLUSIONS

Solar urticaria is characterized by rapid signal transducer and activator of transcription 3 activation in mast cells and involvement of multiple chemotactic and innate inflammatory pathways, with FcεRI engagement indicated as an early event.

Immunopathogenesis of urticaria: a clinical perspective on histamine and cytokine involvement

BACKGROUND

Urticaria is a clinical condition characterized by the appearance of wheals (hives), angioedema, or both. Over the last several decades, a better understanding of the mechanisms at play in the immunopathogenesis of urticaria has underscored the existence of numerous urticaria subtypes. Separating the different kinds of urticaria explicitly helps find the best detection method for the management of this skin disorder. Subtypes of urticaria also include both spontaneous and physical types. The conventional ones include spontaneous urticaria, constituting both acute and chronic urticaria. Therefore, a broad and effective therapy is essential for the diagnosis and treatment of urticaria.

METHODS

To understand the immunopathogenesis of urticaria, various databases, including PubMed, Scopus, and Web of Science, were used to retrieve original articles and reviews related to urticaria. While information on several clinical trials were obtained from clinicaltrials.gov database.

RESULTS

This article highlights the immunopathogenesis involved in the intricate interaction between cellular infiltration, immune reactions, coagulation cascades, and autoantibodies that underlie urticaria's pathophysiology.

CONCLUSION

The recent progress in understanding urticaria can help to understand the intricate characteristics in the immunopathogenesis of urticaria and could play a beneficial role in the management of urticaria.

Extracorporeal Photopheresis in Dermatological Diseases

Extracorporeal photopheresis (ECP) is an apheresis procedure that is conventionally used as a first-line treatment for cutaneous and leukemic subtypes of T-cell lymphoma, such as Sezary's syndrome and mycosis fungoides. Over the past three decades, its immunotherapeutic properties have been tested on a variety of autoimmune conditions, including many dermatologic diseases. There is ample evidence of ECP's ability to modify leukocytes and alter cytokine production for certain dermatologic diseases that have been refractory to first-line treatments, such as atopic dermatitis. However, the evidence on the efficacy of ECP for the treatment of these dermatologic diseases is unclear and/or lacks sufficient evidence. The purpose of this paper is to review the literature on the utilization and clinical efficacy of ECP in the treatment of several [autoimmune] dermatologic diseases and discuss its applications, guidelines, recommendations, and future implementation for dermatologic diseases.

Solar Urticaria: An Ambispective Study in a Long-term Follow-up Cohort with Emphasis on Therapeutic Predictors and Outcomes

Solar urticaria is a rare photodermatosis with several unknown pathogenic, clinical and therapeutic aspects. This study analysed the clinical and therapeutic features of a long-term follow-up solar urticaria cohort, with a focus on omalizumab management and outcomes, and characterized omalizumab response with the use of the high-affinity immunoglobulin E (IgE) receptor (FcεRI) and the Urticaria Control Test. An observational, unicentric, ambispective study was conducted from 2007 to 2023. Solar urticaria was diagnosed in 41 patients with a median follow-up of 60 months. Thirteen patients were prescribed omalizumab, with a median treatment time of 48 months. A significant decrease in FcεRI baseline levels and subsequent median increase in Urticaria Control Test was evidenced after omalizumab prescription in all patients. Drug survival at 48 months was at 88.9%. Omalizumab stepping-down protocol led to sustained omalizumab discontinuation in only 1 patient. Median basal Urticaria Control Test was lower (p < 0.01) in patients who were prescribed omalizumab and in patients without remission. This study contributes to our knowledge of omalizumab outcomes in real-life clinical practice and highlights the pathogenic importance of IgE-mediated pathways in solar urticaria, where FcεRI emerges as a possible biomarker of omalizumab response.

Recent updates in urticaria

Urticaria is a skin-condition characterized by sudden-onset pruritic wheals with/without angioedema. Urticaria can be acute or chronic. Chronic urticaria may be spontaneous or inducible, based on absence/presence of specific triggers. Chronic spontaneous urticaria is most frequent (∼80%). Urticaria is primarily a mast-cell mediated histaminergic-disorder. Recently, other inflammatory cells and pro-inflammatory cytokines have been implicated. Deeper understanding has unmasked two endotypes - IgE-mediated type I autoimmunity/autoallergy and IgG-mediated type IIb autoimmunity. Current treatment recommendation involving second-generation H1-antihistamines, omalizumab and cyclosporine is effective in 60-80% patients. So, newer treatment options are being explored based on emerging targets. Despite being non-lethal, urticaria considerably impairs patient's quality-of-life and may be associated with extra-cutaneous comorbidities. Several "patient reported outcome measures" have been proposed to evaluate disease-activity, impact and control, for effective treatment modulation till complete disease control. This review discusses the current understanding about urticaria and its future directions, to facilitate optimum evidenced-based care.

Urticaria

Urticaria is an inflammatory skin disorder that affects up to 20% of the world population at some point during their life. It presents with wheals, angioedema or both due to activation and degranulation of skin mast cells and the release of histamine and other mediators. Most cases of urticaria are acute urticaria, which lasts ≤6 weeks and can be associated with infections or intake of drugs or foods. Chronic urticaria (CU) is either spontaneous or inducible, lasts >6 weeks and persists for >1 year in most patients. CU greatly affects patient quality of life, and is linked to psychiatric comorbidities and high healthcare costs. In contrast to chronic spontaneous urticaria (CSU), chronic inducible urticaria (CIndU) has definite and subtype-specific triggers that induce signs and symptoms. The pathogenesis of CSU consists of several interlinked events involving autoantibodies, complement and coagulation. The diagnosis of urticaria is clinical, but several tests can be performed to exclude differential diagnoses and identify underlying causes in CSU or triggers in CIndU. Current urticaria treatment aims at complete response, with a stepwise approach using second-generation H1 antihistamines, omalizumab and cyclosporine. Novel treatment approaches centre on targeting mediators, signalling pathways and receptors of mast cells and other immune cells. Further research should focus on defining disease endotypes and their biomarkers, identifying new treatment targets and developing improved therapies.