Chronic Spontaneous Urticaria: The Role and Relevance of Autoreactivity, Autoimmunity, and Autoallergy

Clinical phenotypes and biomarkers in chronic urticaria

The medical field faces considerable challenges in treating chronic urticaria (CU), which includes both chronic spontaneous urticaria (CSU) and chronic inducible urticaria, owing to its varied nature. The complexity of this condition stems from multiple factors: varying disease mechanisms, different ways in which symptoms manifest, and inconsistent treatment outcomes. Although both forms of CU display hives that persist beyond six weeks, they have distinct causes and progression patterns. This study examines CSU specifically, exploring its various manifestations and associated biological indicators. Currently, there is a pressing need to identify reliable, accessible biomarkers for CSU to enhance diagnosis and develop targeted treatments. Better insights into how specific disease patterns are related to biological markers would significantly improve our understanding of CSU development and enhance patient treatment approaches.

Endotypes, phenotypes, and biomarkers in chronic spontaneous urticaria: Evolving toward personalized medicine

Chronic spontaneous urticaria (CSU) is an inflammatory disorder that manifests with hives, angioedema, or both and lasts more than or equal to 6 weeks. Although certain elements of CSU pathogenesis are well defined, others remain unclear. We discuss our current understanding of the underlying CSU endotypes, distinct clinical phenotypes, and predictive biomarkers. It is increasingly recognized that CSU comprises a spectrum of different underlying pathogenic mechanisms and distinct clinical presentations. Broadly, 2 endotypes that drive CSU pathogenesis have been identified, namely type I (autoallergic) and type IIb (autoimmune). However, a subpopulation shows evidence of both types, and some patients show evidence of neither. Multiple identified biomarkers have been associated with these endotypes or with disease features, such as CSU severity and duration. There is a lack of connectivity among the identified biomarkers, genetic risk loci, phenotypes, and corresponding endotypes, and each of these is frequently considered independently of the others. These identifiable features also have been associated with response, or lack thereof, to available therapies. Future investigations should optimize the endotyping of CSU using point-of-care, noninvasive, accessible biomarkers and assess the differences in response to therapy. With multiple treatments in late-stage development, establishing clearly defined CSU endotypes will facilitate future treatment decision-making and tailored treatment approaches and will inform optimal trial design.

The Role of Coagulation/Fibrinolysis Biomarkers in Pathophysiology, Disease Severity, and Treatment Response in Patients with Urticaria: A Scoping Review

The pathology of urticaria is complex. Recently, researchers have widely focused on the role that the coagulation/fibrinolysis system plays in the pathology of urticaria. The potential of coagulation/fibrinolysis biomarkers as disease severity or treatment response biomarkers remains uncertain, lacking comprehensive analysis in previous studies. Hence, we performed a scoping review to thoroughly analyze coagulation/fibrinolysis biomarkers that may predict disease progression and treatment response of urticaria. Data from 71 studies showed that chronic spontaneous urticaria (CSU) was the most-studied subtype (39 articles), with D-dimers being the most researched marker (56 articles). Twenty-one biomarkers were investigated, and ten biomarkers were significantly correlated with disease severity. Specifically, D-dimers (26 articles) and prothrombin fragment 1 + 2 (F1+2) (12 articles) plasma levels increased with exacerbation and decreased with remission. Biomarkers such as D-dimer also correlated significantly with inflammatory cytokines and complement, suggesting interactions among coagulation, immunity, and inflammation in the pathology of urticaria. While these biomarkers may predict treatment response, more evidence is needed. Additionally, anticoagulants such as warfarin, heparin sodium and tranexamic acid have been proved effective for urticaria. This review emphasizes that some coagulation/fibrinolysis biomarkers (such as D-dimer and F1+2) may be not only indicators of disease status but also potential predictors of treatment response. It aims to assist researchers and practitioners in gaining a better understanding of the close relationships among coagulation/fibrinolysis biomarkers, the condition of urticaria (especially chronic urticaria, CU), and its prognosis. It also provides new directions for future research on exploring treatment methods via the coagulation/fibrinolysis pathways.

Treatment of patients with evidence of mast cell-mediated itch in the absence of hives with omalizumab

PURPOSE

The presence of wheals or hives has been viewed as a hallmark symptom of urticaria, a highly debilitating disease. This study explores our experience with omalizumab in patients with apparent mast-cell mediated pruritus in the absence of hives.

MATERIALS AND METHODS

This is a retrospective case series examining all patients with mast cell-mediated pruritus in the absence of hives from April 2022 to May 2024 at a tertiary referral clinic at Icahn School of Medicine at Mount Sinai in New York. Peak pruritus-numerical rating scale (PP-NRS) itch score changes over time were recorded and analyzed.

RESULTS

Six patients (67% women; mean [SD] age, 47.67 [13.52] years) were included in the analysis. The median [IQR] pruritus PP-NRS itch score before omalizumab injection was 9 [6 - 10] and the final median [IQR] PP-NRS itch score was 2.5 [0 - 5]. The mean [SD] reduction in the PP-NRS itch score was 6 [3.16].

CONCLUSIONS

This study suggests that patients with evidence of mast cell-mediated pruritus can be identified based on clinical features and may benefit from omalizumab therapy.

Role of Platelet-Activating Factor in the Pathogenesis of Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is a debilitating condition characterized by mast cell activation. Platelet-activating factor (PAF) is produced by various immune cells, including mast cells, basophils, lymphocytes, and eosinophils, which play crucial roles in CSU pathogenesis. It induces mast cell degranulation, increases vascular permeability, and promotes the chemotaxis of inflammatory cells. These effects result in the release of inflammatory mediators, the development of edema, and the persistence of inflammation, which are key features of CSU. Notably, elevated PAF levels have been linked to heightened disease activity and resistance to antihistamine treatment in CSU patients. Despite these findings, the precise role of PAF in CSU pathogenesis remains unclear. Rupatadine, an antihistamine, and heat shock protein 10, a natural anti-inflammatory peptide that selectively inhibits PAF-induced mast cell degranulation, have demonstrated anti-PAF activity. Furthermore, with the molecular structure of the PAF receptor now identified, several experimental PAF receptor antagonists have been synthesized. However, there remains a significant need for the development of therapeutic options targeting PAF in CSU management.

Distinct Clinical Profiles of IgE and IgG Autoantibodies to Thyroid Peroxidase in Chronic Spontaneous Urticaria

PURPOSE

In chronic spontaneous urticaria (CSU), autoimmune thyroid disease is the most common autoimmune comorbidity, and many CSU patients have immunoglobulin (Ig)E or IgG autoantibodies to thyroid peroxidase (TPO). It remains unclear how anti-TPO IgE and IgG autoantibodies are linked to each other and are associated with CSU features, activity, and therapeutic responses.

METHODS

CSU patients (n = 146, 92 females, mean age 42.9 years) and healthy normal controls (NCs, n = 30) were assessed for anti-TPO IgE and IgG by enzyme-linked immunosorbent assay, and the clinical and laboratory profiles, disease activity (UAS7), and response to 3 months of H1-antihistamine treatment were evaluated for anti-TPO IgE-positive and/or IgG-positive patients.

RESULTS

Among 146 CSU patients, 67 (46%, NCs: 6.6%) had elevated anti-TPO IgE and/or IgG, and 32 (22%), 35 (24%), and 5 (3%) had elevated anti-TPO IgE, anti-TPO IgG, and both, respectively. Of the patients with anti-TPO IgE and/or IgG, 44% (n = 27) had anti-TPO IgE but not IgG, 48% (n = 30) had anti-TPO IgG but not IgE, and only 8% (n = 5) had anti-TPO IgE and IgG. Compared to anti-TPO IgE-negative patients, anti-TPO IgE-positive ones had greater rates of atopy and antihistamine responses and lower disease activity (UAS7). Anti-TPO IgG-positive patients had greater rates of angioedema and elevated levels of anti-thyroglobulin IgG than anti-TPO IgG-negative patients.

CONCLUSIONS

Forty-six percentages of CSU patients have autoantibodies to TPO; most have either IgE or IgG autoantibodies but not both. Anti-TPO IgE and anti-TPO IgG come with distinct CSU profiles, including treatment responses.

Chronic Spontaneous Urticaria: Current and Emerging Biologic Agents

Antihistamine refractory chronic spontaneous urticaria (CSU) has a prevalence of up to 50%. Anti-immunoglobulin E (IgE) therapies have revolutionized management of CSU, yet refractory cases persist, suggesting a role for biologic agents that impact alternative routes of mast cell stimulation independent of cross-linking at FcεR1. This review addresses anti-IgE and Th2-targeted therapies in the management of CSU. In addition, we explore novel treatments targeting alternative pathways of mast cell activation including MAS-related G protein-coupled receptor-X2 and sialic acid-binding immunoglobulin-like lectin-6, inhibiting intracellular signaling via Bruton's tyrosine kinase, and disrupting KIT activation by SCF.

Key differences between chronic inducible and spontaneous urticaria

Introduction

The latest international EAACI/GA²LEN/EuroGuiDerm/APAAACI guideline for urticaria recommends limited laboratory testing for chronic spontaneous urticaria (CSU) and selective testing for only certain chronic inducible urticaria (CIndU) subtypes, though the rationale for these recommendations is poorly explained. This study aimed to improve the understanding of CIndU subtypes by comprehensively comparing their demographic, clinical, and laboratory characteristics with those of the better-characterized CSU.

Methods

We conducted a retrospective analysis of 567 patients (median age 41 years, 67% female) diagnosed with CSU, symptomatic dermographism (SD), cold urticaria (ColdU), cholinergic urticaria (CholU), and delayed pressure urticaria (DPU).

Results

Our findings revealed that patients with SD, ColdU, and CholU had lower levels of C-reactive protein (CRP), higher total serum immunoglobulin E (IgE) levels, and higher basophil counts compared to CSU patients. These subtypes also had distinct demographic and clinical features, such as a younger age of onset and a longer disease duration. In contrast, patients with DPU had significantly higher CRP levels and neutrophil counts compared to those with CSU.

Discussion

These findings highlight the heterogeneity among chronic urticaria subtypes, suggesting that a tailored approach to laboratory testing may be more effective. The distinct immunological and clinical features observed in CIndU subtypes suggest a need for subtype-specific diagnostic and therapeutic guidelines.

Disease modification in chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is a debilitating, inflammatory skin condition characterized by infiltrating immune cells. Available treatments are limited to improving the signs and symptoms. There is an unmet need to develop therapies that target disease-driving pathways upstream of mast cell activation to inhibit or delay the progression of CSU and associated comorbidities. Here, we aim to define disease modification due to a treatment intervention and criteria that disease-modifying treatments (DMTs) must meet in CSU. We have defined disease modification in CSU as a favorable treatment-induced change in the underlying pathophysiology and, therefore, the disease course, which is clinically beneficial and enduring. A DMT must fulfil the following criteria: (1) prevents or delays the progression of CSU, (2) induces long-term, therapy-free clinical remission, which is the sustained absence of CSU signs and symptoms without the need for treatment, and (3) affects the underlying mechanism of CSU, as demonstrated by an effect on disease-driving signals and/or a biomarker. DMTs in CSU should slow disease progression, achieve long-lasting disease remission, target disease-driving mechanisms, reduce mast cell-activating IgE autoantibodies, target cytokine profile polarization, and normalize the gut microbiome and barrier. Treating CSU at the immune system level could provide valuable alternatives to pharmacotherapy in CSU management. Specific DMTs in CSU are yet to be developed, but some show potential benefits, such as inhibitors of Bruton's Tyrosine Kinase, IL-4 and IL-13. Future therapies could prevent CSU signs and symptoms, achieve long-term clinical benefits after discontinuing treatment, and prevent associated concomitant disorders.

Characteristics and Clinical Significance of Atopy in Chronic Spontaneous Urticaria: A Cross-Sectional Observational Study

INTRODUCTION

Atopy is an important and non-negligible clinical phenomenon in chronic spontaneous urticaria (CSU). However, the characteristics and clinical significance of atopy in patients with CSU have not been fully described. This study aimed to analyze the characteristics and clinical significance of atopy in patients with CSU.

METHODS

A descriptive cross-sectional design was used. The study enrolled 176 patients with CSU. All enrolled patients underwent total IgE, specific IgE, and autologous serum skin tests (ASSTs). The relationships between atopy, the demographic and clinical data of patients with CSU, and the response to ASST were analyzed in detail; the distribution of allergens in atopic CSU was also analyzed.

RESULTS

Atopy was confirmed in 48.9% of patients with CSU. Patients with atopic CSU were more likely than patients with non-atopic CSU to have dermatographism (57.0% vs. 41.1%, p < 0.05), history of urticaria (37.2% and 18.9%, respectively; p < 0.01), angioedema (39.5% and 24.4%, respectively; p < 0.05), and anaphylaxis (7/86 and 1/90, respectively; p < 0.05). Atopy was not associated with ASST response, disease duration, or response to antihistamine treatment in patients with CSU, nor was it associated with the urticaria activity score (UAS7), chronic urticaria quality of life questionnaire (CU-Q2oL), or pruritus visual analog scale (VAS) scores (all p < 0.05). The most common allergen in patients with atopic CSU was dust mites, followed by animal food allergens, tree/grass pollen, and cockroaches.

CONCLUSIONS

Although larger prospective studies are needed to confirm these results, our study found atopy occurred in nearly half of patients with CSU, and preliminarily links atopy to CSU, suggesting it as a potential risk factor for angioedema, anaphylaxis, and recurrent urticaria, mirroring allergen patterns in other allergic disease.

Assessment of ELR, PLR, NLR and BLR Ratios during Omalizumab Treatment of Chronic Spontaneous Urticaria

Background: There is a need for searching for biomarkers indicating patients who will benefit the most from treatment with omalizumab for chronic spontaneous urticaria (CSU). The aim of this study was to assess whether the eosinophil/neutrophil/platelet/basophil-to-lymphocyte ratio (ELR, NLR, PLR, BLR) may predict the response to omalizumab treatment of chronic spontaneous urticaria. Methods: A retrospective data analysis of CSU patients treated s-c with 300 mg of omalizumab every four weeks under the drug program was carried out. NLR, ELR, PLR and BLR, DLQI, UAS-7, CRP, anti-TPO and tIgE were assessed before (V0) and after three (V3) and six months (V6) of treatment. Results: Among 52 patients with CSU, 21 were responders, 24 were partially responders and 6 were non-responders to treatment with 300 mg omalizumab every four weeks. An amount of 18 patients had features of type I autoallergic CSU (CSUaiTI) and 34 patients had autoimmunity type IIb CSU with mast cell-directed activating autoantibodies (CSUaiTIIb). NLR, ELR, PLR and BLR indices did not change during a six-month-course of biological treatment. Initial values of ELR and BLR were significantly correlated with the initial tIgE level and anti-TPO/IgE ratio. Initial values of NLR, ELR and BLR were significantly correlated with initial CRP. Comparisons between type I autoallergic CSU (CSUaiTI) and autoimmunity type IIb CSU (CSUaiTIIb) revealed that the absolute number and percentage of eosinophils, basophils, BLR and tIgE were significantly higher in type CSUaiTI and anti-TPO and anti-TPO/IgE were significantly lower in type CSUaiTI. Conclusions: NLR, ELR, PLR and BLR do not change significantly during six months of omalizumab treatment and do not appear to be useful in predicting its efficacy.

Detecting Changes in Mast Cell Numbers Versus Activation in Human Disease: A Roadblock for Current Biomarkers?

The pathophysiology of mast cell (MC)-driven disorders is diverse, ranging from localized reactions to systemic disorders caused by abnormal accumulation and activation in multiorgan systems. Prompt and accurate diagnosis is critically important, both for informing treatment and objective assessment of treatment outcomes. As new therapeutics are being developed to deplete MCs or silence them (eg, by engaging inhibitory receptors that block activation), new biomarkers are needed that can distinguish between MC activation versus burden. Serum tryptase is the gold standard for assessing both MC burden and activation; however, commercial tryptase assays have limitations related to timing of release, lack of discernment between inactive (α) and active (β) forms of tryptase, and interpatient variability of baseline levels. Alternative approaches to measuring MC activation include urinary MC mediators, flow cytometry-based assays or gene expression profiling. Additional markers of MC activation are needed for use in clinical diagnostics, to help selection of treatment of MC diseases, and for assessing outcomes of therapy. We review the spectrum of disorders with known or suspected MC contribution, describe the utility and limitations of current MC markers and assays, and discuss the need for new markers that can differentiate between MC activation and burden.

Bruton's tyrosine kinase inhibition for the treatment of allergic disorders

IgE signaling through its high-affinity receptor FcεRI is central to the pathogenesis of numerous allergic disorders. Oral inhibitors of Bruton's tyrosine kinase (BTKis), which are currently Food and Drug Administration-approved for treating B cell malignancies, broadly inhibit the FcεRI pathway in human mast cells and basophils, and therefore may be effective allergen-independent therapies for a variety of allergic diseases. The application of these drugs to the allergy space was previously limited by the low kinase selectivity and subsequent toxicities of early-generation compounds. Fortunately, next-generation, highly selective BTKis in clinical development appear to have more favorable risk-benefit profiles, and their likelihood of being Food and Drug Administration-approved for an allergy indication is increasing. Recent clinical trials have indicated the remarkable and rapid efficacy of the second-generation BTKi acalabrutinib in preventing clinical reactivity to peanut ingestion in adults with peanut allergy. In addition, next-generation BTKis including remibrutinib effectively reduce disease activity in patients with antihistamine-refractory chronic spontaneous urticaria. Finally, several BTKis are currently under investigation in early clinical trials for atopic dermatitis and asthma. In this review, we summarize recent data supporting the use of these drugs as novel therapies in food allergy, anaphylaxis, urticaria, and other allergic disorders. We also discuss safety data derived from trials using both short-term and chronic dosing of BTKis.

A Practical Approach to Diagnosing and Managing Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is an unpredictable inflammatory skin condition characterized by the spontaneous onset of itchy wheals, angioedema, or both, which occurs for longer than 6 weeks overall. Despite the relatively straightforward diagnostic algorithm for CSU, relying primarily on a detailed medical history and only limited laboratory tests, patients often wait years to be diagnosed, with many cycling through different healthcare practitioners before a diagnosis is made. Even then, current treatment options for CSU are limited, with approximately half of patients resistant to standard-of-care second-generation antihistamines at standard or higher doses. As such, there is an unmet need for improved, streamlined management for patients with CSU. Here, we review the evidence-based diagnostic algorithm for CSU, consider the required steps of the diagnostic workup, and provide practical, real-world advice on the management of CSU to improve the timely diagnosis and care of patients with this debilitating disease.

Associations of Gut and Circulating Microbiota with Circulating Vitamin D3, Type I Interferon, and Systemic Inflammation in Chronic Spontaneous Urticaria Patients

Objective

To analyze the associations of the gut and circulating microbiota with circulating vitamin D3 (VD3), type I interferon (IFNI), systemic inflammation, and clinical profiles in chronic spontaneous urticaria (CSU) patients.

Methods

A total of 36 CSU patients with VD3 insufficiency (VDI; serum 25(OH)VD3 <30 ng/mL) and 36 sex-, age-, and body mass index-matched CSU patients with non-VDI were enrolled. Fecal and serum bacteria were identified through 16S rRNA sequencing, and serum 25(OH)VD3 and inflammation biomarkers were assessed using ELISA kits. IFNI response was determined by measuring the stimulatory activity of serum on IFNI-stimulated response element in HEK293 cells in vitro with luciferase assays.

Results

Higher urticarial activity score over 7 days (UAS7), higher frequency of levocetirizine resistance, and more severe proinflammation but weaker IFNI response were observed in VDI than non-VDI patients (all P<0.05). IFNI response was strongly positively associated with serum 25(OH)VD3 level in both groups (P<0.001). Compared to non-VDI patients, abundance of the fecal genera Prevotella 9, Escherichia-Shigella, and Klebsiella was significantly increased, while Bacteroides, Faecalibacterium, and Agathobacter were remarkably reduced in VDI patients (all P<0.05). Burkholderia-Caballeronia-Paraburkholderia (40.95%), Acinetobacter (3.05%), and Aquabacterium (2.37%) were the top three bacteria in sera from VDI patients. Both serum 25(OH)VD3 level and IFNI response were positively associated with fecal Bacteroides in the two groups (P<0.05). In non-VDI patients, there were moderately positive associations between IFNI response and fecal Lachnoclostridium, unclassified_f__Lachnospiraceae, and Phascolarctobacterium and between serum 25(OH)VD3 level and fecal Lachnoclostridium (all P<0.01). Circulating microbiota in VDI patients was closely related only to proinflammation and UAS7 (both P<0.05).

Conclusion

Changes in gut but not circulating microbiota composition are associated with serum 25(OH)VD3 insufficiency and impaired IFNI homeostasis, which points to greater disease severity (UAS7) and systemic proinflammation in CSU patients.

Biologic therapy for chronic spontaneous urticaria in pediatrics and adolescents: current landscape, challenges, and future perspectives

INTRODUCTION

Chronic spontaneous urticaria (CSU) poses significant challenges, especially in pediatric and adolescent patients, impacting physical, emotional, and social well-being. Recent biologic breakthroughs offer promise, however, data on safety and efficacy in this population remain limited.

AREAS COVERED

This review examines current biologic treatments in pediatrics and adolescents with CSU and explores the rapidly emerging landscape.

EXPERT OPINION

Despite omalizumab's approval for allergic asthma in children since 2009, its delayed approval for CSU raises questions. Ligelizumab, a next-generation anti-IgE mAb, showed effectiveness in adults but lacks pediatric studies. CT-P39, a biosimilar to omalizumab, demonstrates promise, yet adolescent-specific outcomes are undisclosed. Dupilumab's recent approval for atopic dermatitis in children from 6 months onwards signifies progress. Expert opinion underscores the scarcity of controlled trials in pediatric and adolescent CSU, emphasizing the need for comprehensive studies. Age-specific data and collaboration are crucial for addressing research gaps and expanding indications for pediatric CSU treatment. The recently validated UAS7 parameter in children marks a milestone for prospective clinical trials. Despite challenges, the biology therapy outlook for pediatric and adolescent CSU is promising. Importantly, studies indicate that pediatric CSU is at least as prevalent as in adults, highlighting the need for approved treatments in this population.

An update on the use of antihistamines in managing chronic urticaria

INTRODUCTION

Urticaria, a mast cell-mediated skin disease, manifests as acute or chronic, with the latter divided into spontaneous and inducible types and requires individualized management, including identifying triggers and comorbidities. Antihistamines, particularly the second generation group, form the mainstay of primary treatment plans consisting of dosage adjustments and/or in combination with other treatment modalities depending on underlying disease control.

AREAS COVERED

A literature search was conducted using 'antihistamines,' 'urticaria,' 'pharmacogenomics,' 'genomics,' 'biomarkers' and 'treatment response' as key words. In this review, we focus on the comprehensive understanding and application of antihistamines in managing adult and adolescent patients with chronic urticaria.

EXPERT OPINION

Using antihistamines to treat urticaria is set to change significantly, focusing more on personalized medicine and identifying key biomarkers to enhance treatment response prediction. These changes aim to make treatments more specific and cost-effective by avoiding unnecessary tests. Applying new approaches in everyday clinical care faces challenges like proving the biomarkers' reliability, updating current guidelines, and incorporating individualized treatments into standard procedures. Efforts should now concentrate on finding easy-to-use biomarkers, improving access to pharmacogenomics, understanding why some patients are resistant to treatment, and creating more specific treatment options based on patient needs.

Mechanisms of histamine release from mast cells beyond the high affinity IgE receptor in severe chronic spontaneous urticaria

There is growing evidence suggesting that in a subset of patients with severe chronic urticaria [CSU] mast cells are activated via mechanisms that bypass the high affinity IgE receptor. This might explain why some patients do not respond at all to anti-IgE therapy [omalizumab]. The present article reviews the pathogenic mechanisms able to lead to histamine release from mast cells described so far in patients with CSU. These include the activation of the coagulation cascade, the activation of the complement system, the activation of the MRGPRX2 receptor, and the platelet activating factor vicious circle. The article suggests some possible interpretations for the clinical events occurring in this specific subset of patients.

Chronic spontaneous urticaria: Evidence of systemic microcirculatory changes

BACKGROUND

Chronic spontaneous urticaria (CSU) is a chronic inflammatory skin disease where activation of endothelial cells (ECs) at sites of skin lesions leads to increased blood flow, leakage of fluid into the skin, cellular infiltration, and vascular remodeling. To understand the disease duration and the sometimes vague systemic symptoms accompanying flares, the objective of this study was to examine if CSU comes with systemic vascular changes at the microcirculatory level.

METHODS

We investigated CSU patients (n = 49) and healthy controls (HCs, n = 44) for microcirculatory differences by nailfold videocapillaroscopy (NVC) and for blood levels of the soluble EC biomarkers serum vascular endothelial growth factor (VEGF), soluble E-selectin, and stem cell factor (SCF). Patients were also assessed for clinical characteristics, disease activity, and markers of autoimmune CSU (aiCSU).

RESULTS

CSU patients had significantly lower capillary density, more capillary malformations, and more irregular capillary dilations than HCs on NVC. Serum levels of VEGF, soluble E selectin and SCF were similar in CSU patients and HCs. CSU patients with higher VEGF levels had significantly more abnormal capillaries. Patients with markers of aiCSU, that is, low IgE levels or increased anti-TPO levels, had significantly more capillaries and less capillary dilations than those without.

CONCLUSION

Our results suggest that CSU comes with systemic microcirculatory changes, which may be driven, in part, by VEGF.

Mast cell silencing: A novel therapeutic approach for urticaria and other mast cell-mediated diseases

Chronic urticaria (CU) is a mast cell (MC)-dependent disease with limited therapeutic options. Current management strategies are directed at inhibiting IgE-mediated activation of MCs and antagonizing effects of released mediators. Due to the complexity and heterogeneity of CU and other MC diseases and mechanisms of MC activation-including multiple activating receptors and ligands, diverse signaling pathways, and a menagerie of mediators-strategies of MC depletion or MC silencing (i.e., inhibition of MC activation via binding of inhibitory receptors) have been developed to overcome limitations of singularly targeted agents. MC silencers, such as agonist monoclonal antibodies that engage inhibitory receptors (e.g., sialic acid-binding immunoglobulin-like lectin8 -[Siglec-8] [lirentelimab/AK002], Siglec-6 [AK006], and CD200R [LY3454738]), have reached preclinical and clinical stages of development. In this review, we (1) describe the role of MCs in the pathogenesis of CU, highlighting similarities with other MC diseases in disease mechanisms and response to treatment; (2) explore current therapeutic strategies, categorized by nonspecific immunosuppression, targeted inhibition of MC activation or mediators, and targeted modulation of MC activity; and (3) introduce the concept of MC silencing as an emerging strategy that could selectively block activation of MCs without eliciting or exacerbating on- or off-target, immunosuppressive adverse effects.

Autoimmune Diseases and Low Baseline IgE in Chronic Spontaneous Urticaria: A Clinical and Therapeutic Prospective Analysis in Real-Life Clinical Practice

BACKGROUND

Autoimmunity contributes to the pathogenesis of chronic spontaneous urticaria (CSU). The subtyping of CSU has revealed an autoimmune form of CSU. Despite autoimmune diseases having been associated with CSU, there are few prospective studies that have evaluated the characteristics and biomarkers of patients with CSU and autoimmune disease in a real-life practice setting.

OBJECTIVE

To evaluate the presence of specific biomarkers for the presence of autoimmune disease in CSU and to analyze the clinical and therapeutic features of patients with CSU and autoimmune disease.

METHODS

The clinical, laboratory, and therapeutic features of patients with CSU at a tertiary-level center were prospectively collected. Data obtained were compared in function of the presence/absence of autoimmune disease and typified according to IgE levels.

RESULTS

Patients with CSU who had associated autoimmune disease corresponded to middle-aged women with a common pattern of blood test findings: both low baseline IgE and high-affinity receptor of IgE expression, basopenia, eosinopenia, higher baseline erythrocyte sedimentation rate and D-dimer, increased presence of antinuclear antibodies, IgG against thyroid peroxidase, and positive autologous serum skin test result. Total baseline IgE less than or equal to 43.8 IU/mL was both the optimal cutoff to predict autoimmune disease in the CSU cohort and a significant risk factor for the presence of autoimmune disease in the regression analysis.

CONCLUSIONS

In real-life clinical practice, characteristics of patients with CSU and autoimmune disease share common features with type IIb autoimmune CSU. Total baseline IgE less than or equal to 43.8 IU/mL has been detected as a possible biomarker of autoimmune disease in patients with CSU.

Autoreactive IgE: Pathogenic role and therapeutic target in autoimmune diseases

Autoimmunity is the break of tolerance to self-antigens that leads to organ-specific or systemic diseases often characterized by the presence of pathogenic autoreactive antibodies (AAb) produced by plasmablast and/or plasma cells. AAb are prevalent in the general population and not systematically associated with clinical symptoms. In contrast, in some individuals, these AAb are pathogenic and drive the development of signs and symptoms of antibody-mediated autoimmune diseases (AbAID). AAb production, isotype profiles, and glycosylations are promoted by pro-inflammatory triggers linked to genetic, environmental, and hormonal parameters. Recent evidence supports a role for pathogenic AAb of the IgE isotype in a number of AbAID. Autoreactive IgE can drive the activation of mast cells, basophils, and other types of FcεRI-bearing cells and may play a role in promoting autoantibody production and other pro-inflammatory pathways. In this review, we discuss the current knowledge on the pathogenicity of autoreactive IgE in AbAID and their status as therapeutic targets. We also highlight unresolved issues including the need for assays that reproducibly quantify IgE AAbs, to validate their diagnostic and prognostic value, and to further study their pathophysiological contributions to AbAID.

Biomarkers of Autoimmune Chronic Spontaneous Urticaria

PURPOSEOF REVIEW

Chronic spontaneous urticaria and chronic inducible urticaria (CSU/CindU) are caused by mast cell and basophil activation leading to degranulation and the release of histamine and several other mediators. Three kinds of factors can trigger mast cells in CSU: (1) activation of stimulating receptor(s) on the mast cell membrane, (2) upregulation of certain receptor(s), and (3) intracellular dysregulation in signaling with overexpression of the spleen tyrosine kinase (SYK) or reduced activation of the inhibitory Src homology 2 (SH2)-containing inositol phosphatases (SHIP)-related pathways. In CSU, two major endotypes exist based on the primary receptor activating mechanism: type I hypersensitivity (IgE-mediated, directed against auto-allergens) and type IIb (autoimmune, via IgG autoantibodies directed against IgE or the IgE-receptor). Their treatment responses vary. We discuss in vitro and in vivo biomarkers.

RECENT FINDINGS

Patients with auto-allergic CSU have clinical characteristics that can distinguish them partly from those with autoimmune CSU. Most importantly, their disease generally presents a less aggressive course, a better response to second generation (up-dosed) antihistamines and a good response to omalizumab, if necessary. Meanwhile, autoimmune CSU/CindU patients fare less well and often need immunosuppressive drugs. Biomarkers that might help endotype CSU/CindU patients and select the most appropriate treatment, dose, and duration, e.g., for autoallergic CSU, high total IgE and IgE against auto-allergens; for autoimmune CSU, low IgE, basopenia, and IgG against autoantigens like thyroid peroxidase and a positive autologous serum skin test (but sometimes also positive in autoallergy). Some biomarkers are easily accessible but of low specificity; others are highly specific but more futuristic.

Type I and type IIb autoimmune chronic spontaneous urticaria: Using common clinical tools for endotyping patients with CSU

Background

Mechanisms triggering the pathogenesis of chronic spontaneous urticaria (CSU) have been identified as type I autoallergic (which is associated with IgE antibodies against autoantigens) and type IIb autoimmune (which is driven by autoantibodies to FceR1 and/or IgE).

Objective

Our aim was to define presumptive endotypes in patients with CSU by using tests amenable to use in routine clinical practice.

Methods

A retrospective analysis of the medical records of 394 patients with CSU with or without chronic inducible urticaria or angioedema was performed. Patients were assigned to 1 of 4 groups as follows: (1) type I endotype of CSU, if they presented at least 1 of the following: allergic disease, total IgE level of at least 40UI/mL, and positive result of skin tests to inhalant allergen(s), (2) type IIb endotype of CSU, if they presented at least 1 of following: autoimmune disease, low total IgE level less than 40 IU/mL, positive autologous serum skin test result, positive for antinuclear antibodies in a titer of at least 1:160, and elevated level of anti-thyroid peroxidase, (3) overlap of type I/type IIb endotypes of CSU, if they presented with at least 1 marker of both type I and type IIb, and (4) non-type I/type IIb endotype of CSU, if they presented with none of the markers of type I or type IIb.

Results

The mean age at onset of symptoms was 34 years; 82.2% of those with CSU were female, and angioedema and chronic inducible urticaria were found in 74.8% and 31.9% of patients, respectively. Of the patients with CSU, 38% presented with the type I endotype and 51% presented with type I/type IIb overlap, whereas 9% presented with the type IIb endotype and 2% presented with the non-type I/type IIb endotype. Eosinopenia was associated with type IIb and type I/type IIb overlap as opposed to the type I and non-type I/type IIb endotypes (P = .02).

Conclusions

Most patients with CSU presented with features of the type 1 (autoallergic) endotype, whether associated with type IIb (autoimmune) endotype or not.

Chronic spontaneous urticaria: new evidences on the role of autoimmunity

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of the recent advancements and relevance of the autoimmune theories in chronic spontaneous urticaria (CSU).

RECENT FINDINGS

Two primary types of autoimmunity, Type I and Type IIb, have emerged as major contributors to CSU, characterized by immunoglobulin E (IgE) and immunoglobulin G (IgG) autoantibodies, respectively. Genetic evidence supports the notion that CSU shares more similarities with other autoimmune diseases rather than atopic diseases. Novel autoallergens such as FcεRI and tissue transglutaminase have been identified, contributed to our understanding of autoimmune mechanisms. Furthermore, the potential overlap between Type I and Type IIb autoimmunity has been recognized. Evaluating the autoimmune status of CSU patients through biomarkers and understanding their clinical implications is vital for effective management. For instance, CSU patients with Type IIb autoimmunity, with or without coexisting Type I autoimmunity, may exhibit resistance to H1-antihistamines and omalizumab treatment but could potentially respond well to cyclosporine or Bruton's tyrosine kinase inhibitors.

SUMMARY

Further investigations are needed to explore new autoallergens and autoantibodies in CSU, establishing their connection to the development of autoimmunity. The efficacy of novel drugs targeting different mechanisms should be examined to determine their responses in both autoimmune CSU and nonautoimmunity-related CSU.

Urticaria and basophils

Chronic spontaneous urticaria (CSU) is a common skin disease without an etiology in the vast majority of cases. The similarity of symptoms and pathology to allergen-induced skin reactions supports that skin mast cell IgE receptor activation is also involved in CSU. Accumulating evidence also supports a role for blood basophils in disease expression. Blood basopenia is noted in active CSU disease with the recruitment of blood basophils to skin lesion sites. Blood basophils further display altered IgE receptor mediated degranulation patterns in two phenotypes that improve in remission. In active CSU subjects, changes in IgE receptor signaling molecule expression levels accompany the altered degranulation function in blood basophils. The success of therapies targeting IgE in CSU patients have also shown that altered blood basophil phenotypes and enumeration have potential use as a disease biomarker.