Co-occurrence of IgE and IgG autoantibodies in patients with chronic spontaneous urticaria

BTK signaling-a crucial link in the pathophysiology of chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is an inflammatory skin disorder that manifests with itchy wheals, angioedema, or both for more than 6 weeks. Mast cells and basophils are the key pathogenic drivers of CSU; their activation results in histamine and cytokine release with subsequent dermal inflammation. Two overlapping mechanisms of mast cell and basophil activation have been proposed in CSU: type I autoimmunity, also called autoallergy, which is mediated via IgE against various autoallergens, and type IIb autoimmunity, which is mediated predominantly via IgG directed against the IgE receptor FcεRI or FcεRI-bound IgE. Both mechanisms involve cross-linking of FcεRI and activation of downstream signaling pathways, and they may co-occur in the same patient. In addition, B-cell receptor signaling has been postulated to play a key role in CSU by generating autoreactive B cells and autoantibody production. A cornerstone of FcεRI and B-cell receptor signaling is Bruton tyrosine kinase (BTK), making BTK inhibition a clear therapeutic target in CSU. The potential application of early-generation BTK inhibitors, including ibrutinib, in allergic and autoimmune diseases is limited owing to their unfavorable benefit-risk profile. However, novel BTK inhibitors with improved selectivity and safety profiles have been developed and are under clinical investigation in autoimmune diseases, including CSU. In phase 2 trials, the BTK inhibitors remibrutinib and fenebrutinib have demonstrated rapid and sustained improvements in CSU disease activity. With phase 3 studies of remibrutinib ongoing, it is hoped that BTK inhibitors will present an effective, well-tolerated option for patients with antihistamine-refractory CSU, a phenotype that presents a considerable clinical challenge.

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.

Mast cell signaling and its role in urticaria

Chronic urticaria is a mast cell (MC)-driven disease characterized by the development of itching wheals and/or angioedema. In the last decades, outstanding progress has been made in defining the mechanisms involved in MC activation, and novel activating and inhibitory receptors expressed in MC surface were identified and characterized. Besides an IgE-mediated activation through high-affinity IgE receptor cross-linking, other activating receptors, including Mas-related G-protein-coupled receptor-X2, C5a receptor, and protease-activated receptors 1 and 2 are responsible for MC activation. This would partly explain the reason some subgroups of chronic spontaneous urticaria (CSU), the most frequent form of urticaria in the general population, do not respond to IgE target therapies, requiring other therapeutic approaches for improving the management of the disease. In this review, we shed some light on the current knowledge of the immunologic and nonimmunologic mechanisms regulating MC activation in CSU, considering the complex inflammatory scenario underlying CSU pathogenesis, and novel potential MC-targeted therapies, including surface receptors and cytoplasmic signaling proteins.

Atopy in chronic urticaria: an important yet overlooked issue

Chronic urticaria (CU) is one of the most common dermatological diseases and has a significant impact on the quality of life of patients. However, the pathogenesis of this disease remains unclear. Autoimmunity in chronic spontaneous urticaria (CSU) has received considerable attention and has been studied previously. Atopy is an important characteristic of CU; however, it has not been fully recognized. Atopy predisposes individuals to immune responses to allergens, leading to type 2 inflammation and immunoglobulin E (IgE) overproduction. Compared with healthy individuals, patients with CU have a higher proportion of atopy, and an atopic background is correlated with the clinical characteristics of CU. The total IgE levels in patients with CU is significantly higher than those in healthy individuals. Although its level is not higher than that in classic allergic diseases, it is closely related to CU. Exogenous allergens, auto-allergens, and specific IgEs, which are closely related to atopy, have been reported, and their roles in CU pathogenesis are also being studied. Local and systemic atopic inflammation is present in patients with CU. This review summarizes the current knowledge regarding atopy and CU, speculating that there are CU subtypes, such as atopic CSU or atopic chronic inducible urticaria (CIndU) and that atopy may be involved in the pathogenesis of CU. These findings provide a new perspective for a comprehensive understanding of the clinical features of CU and further research regarding its pathogenesis.

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.

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.

Omalizumab Drug Survival in Chronic Urticaria: A Retrospective Multicentric French Study

BACKGROUND

Omalizumab (OMA) dramatically improves disease control and quality of life in patients with chronic urticaria (CU).

OBJECTIVE

We aimed to evaluate the discontinuation patterns of OMA and their determinants in a cohort of French patients with CU.

METHODS

We conducted a retrospective multicenter study in 9 French tertiary referral hospitals. All patients diagnosed with either spontaneous (CSU) and/or inducible (CIndU) CU who received at least 1 injection of OMA between 2009 and 2021 were included. We analyzed OMA drug survival and investigated possible determinants using Kaplan-Meier curves and log-rank tests.

RESULTS

A total of 878 patients were included in this study; 48.8% had CSU, 10.1% CIndU, and 41.1% a combination of both. OMA was discontinued in 408 patients, but the drug was later reintroduced in 50% of them. The main reason for discontinuing treatment was the achievement of a well-controlled disease in 50% of patients. Half of the patients were still being treated with OMA 2.4 years after the initiation of treatment. Drug survival was shorter in patients with CIndU and in those with an autoimmune background. In atopic patients, OMA was discontinued earlier in patients achieving a well-controlled disease. A longer OMA drug survival was observed in patients with a longer disease duration at initiation.

CONCLUSION

In French patients with CU, the drug survival of OMA appears to be longer than that observed in previous studies conducted elsewhere, highlighting discrepancies in prescription and reimbursement possibilities. Further studies are warranted to develop customized OMA treatment schemes based on individual patterns.

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.

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.

Type 2 chronic inflammatory diseases: targets, therapies and unmet needs

Over the past two decades, significant progress in understanding of the pathogenesis of type 2 chronic inflammatory diseases has enabled the identification of compounds for more than 20 novel targets, which are approved or at various stages of development, finally facilitating a more targeted approach for the treatment of these disorders. Most of these newly identified pathogenic drivers of type 2 inflammation and their corresponding treatments are related to mast cells, eosinophils, T cells, B cells, epithelial cells and sensory nerves. Epithelial barrier defects and dysbiotic microbiomes represent exciting future drug targets for chronic type 2 inflammatory conditions. Here, we review common targets, current treatments and emerging therapies for the treatment of five major type 2 chronic inflammatory diseases - atopic dermatitis, chronic prurigo, chronic urticaria, asthma and chronic rhinosinusitis with nasal polyps - with a high need for targeted therapies. Unmet needs and future directions in the field are discussed.

Clinical Response to Low-dose Omalizumab Treatment in Chronic Spontaneous Urticaria: A Retrospective Study of 179 Patients

Omalizumab is effective in chronic spontaneous urticaria unresponsive to antihistamines. Of the licensed dosing schedules, Korean patients prefer a low dose, of 150 mg/month, for financial reasons. However, real-world experiences of low-dose omalizumab consumption have not been reported. The aim of this retrospective study was to assess the treatment outcomes and long-term clinical course of patients with chronic spontaneous urticaria who were treated with low-dose omalizumab. The study included 179 patients aged ≥ 20 years who were treated with omalizumab 150 mg/month for ≥ 12 weeks. Baseline disease activity was mild, moderate, and severe in 54.7%, 35.2%, and 10.1% of patients, respectively. A complete response was observed in 133 patients at 12 weeks, among whom 88 patients showed early responses within 4 weeks. Overall, 158 patients finally achieved a complete response. Multivariate analyses revealed that baseline disease activity is more likely to be mild in patients who experience early and final complete responses. The absence of atopic comorbidities correlated with an early response. Smoking was associated with a final complete response. This study shows that low-dose omalizumab provides favourable treatment outcomes in antihistamine-refractory chronic spontaneous urticaria. Disease severity, atopic comorbidity, and smoking may be predictive factors for studying the response to omalizumab.

Most Patients With Autoimmune Chronic Spontaneous Urticaria Also Have Autoallergic Urticaria, but Not ViceVersa

BACKGROUND

Two endotypes of chronic spontaneous urticaria (CSU) associated with mast cell-activating autoantibodies are described, namely autoallergic chronic spontaneous urticaria (aaCSU; with immunoglobulin E [IgE]-anti-autoallergens) and autoimmune chronic spontaneous urticaria (aiCSU; with IgG-anti-high-affinity receptor for the Fc region of immunoglobulin E [FcεRI]/IgE).

OBJECTIVE

To investigate the rates of CSU patients with aaCSU and aiCSU.

METHODS

We analyzed 111 CSU patients for aaCSU (ie, IgE to thyroid peroxidase, interleukin 24) and for aiCSU (ie, a positive autologous serum skin and Basophil Activation Test plus immunoglobulin G [IgG]-anti-FcεRI/IgE). Clinical and laboratory parameters were compared in patients with aaCSU, aiCSU, and both.

RESULTS

Across 111 patients with CSU, 64 (58%) had aaCSU and 9 (8%) had aiCSU. Eight of the 9 aiCSU patients had aaCSU, but only 8 of 64 patients with aaCSU had aiCSU. In total, 7% (8 of 111) of patients had both aiCSU and aaCSU, 41% (46 of 111) had neither, and 16% (18 of 111) tested negative for all markers of aaCSU and aiCSU assessed. Patients with aaCSU or aiCSU are different from those without: patients with stand-alone aaCSU tend to be younger than non-aaCSU patients, aiCSU, and aaCSU/aiCSU overlapping subpopulations. In contrast, patients with aiCSU, with or without aaCSU coexistence, are more often female, have higher levels of thyroid peroxidase autoantibodies (both IgG and IgE), and show more severe quality of life impairment.

CONCLUSIONS

Our novel finding that aiCSU coexisting with aaCSU needs to be confirmed in bigger cohorts and multicenter studies. Autoimmunity driven by autoreactive IgE and/or IgG in CSU needs further investigation for better understanding of the pathophysiology.

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

Chronic spontaneous urticaria (CSU) is a frequent and often severely disabling disease. A large number of studies were performed during the last 2 decades to clarify its pathogenesis. These studies shed light on the underlying autoimmune mechanisms of CSU pathogenesis and have led us to understand that different mechanisms may exist and, sometimes, coexist behind the same clinical presentation. The present article reviews the meaning of the terms autoreactivity, autoimmunity, and autoallergy, which have been variably used over the years to define different endotypes of the disease. Furthermore, we discuss the methods potentially able to lead us to the correct classification of CSU patients.

Positive Basophil Tests Are Linked to High Disease Activity and Other Features of Autoimmune Chronic Spontaneous Urticaria: A Systematic Review

BACKGROUND

Chronic spontaneous urticaria (CSU) is believed to be Autoimmune (aiCSU) (type IIb CSU) in at least 8% of patients, associated with mast cell-activating IgG autoantibodies. Basophil tests such as the basophil activation test (BAT) and basophil histamine release assay (BHRA) are considered the best single tests for an aiCSU diagnosis. To date, the strength of associations among a positive BAT and/or BHRA (BAT/BHRA+) and CSU features, patient demographics, and response to treatment remains poorly characterized.

OBJECTIVE

To evaluate the strength of current evidence on basophil tests as parameters for CSU characteristics.

METHODS

We performed a systematic literature search and review to assess the relationship between BAT/BHRA+ and clinical and laboratory parameters of CSU. Of 1,058 records found in the search, 94 studies were reviewed by experts in urticaria and 42 were included in the analysis.

RESULTS

In CSU patients, BAT/BHRA+ showed a strong level of evidence for an association with high disease activity and low levels of total IgE. A weak level of evidence was shown for the association of BAT/BHRA+ and the presence of angioedema, and basopenia.

CONCLUSIONS

Our results suggest that aiCSU defined by BAT/BHRA+ is more active or severe and is linked to other aiCSU markers such as low total IgE/basopenia. Basophil tests should be standardized and implemented in routine clinical care to improve the diagnosis and treatment of patients with aiCSU.

Basophil Characteristics as a Marker of the Pathogenesis of Chronic Spontaneous Urticaria in Relation to the Coagulation and Complement Systems

Chronic spontaneous urticaria (CSU) is a common skin disorder characterized by daily or almost daily recurring skin edema and flare with itch and pruritus anywhere on the body for more than 6 weeks. Although basophil- and mast cell-released inflammatory mediators, such as histamine, play important roles in the pathogenesis of CSU, the detailed underlying mechanism is not clear. Since several auto-antibodies, IgGs which recognize IgE or the high-affinity IgE receptor (FcεRI) and IgEs against other self-antigens, are detected in CSU patients, they are considered to activate both mast cells in the skin and basophils circulating in the blood. In addition, we and other groups demonstrated that the coagulation and complement system also contribute to the development of urticaria. Here, we summarized the behaviors, markers and targets of basophils in relation to the coagulation-complement system, and for the treatment of 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.

Chronic urticaria and the pathogenic role of mast cells

The signs and symptoms of chronic urticaria (CU) are caused by the activation and degranulation of skin mast cells (MCs). Recent studies have added to our understanding of how and why skin MCs are involved and different in CU. Also, novel and relevant mechanisms of MC activation in CU have been identified and characterized. Finally, the use of MC-targeted and MC mediator-specific treatments has helped to better define the role of the skin environment, the contribution of specific MC mediators, and the relevance of MC crosstalk with other cells in the pathogenesis of CU. Here, we review these recent findings and their impact on our understanding of CU, with a focus on chronic spontaneous urticaria (CSU). Also, we highlight open questions, issues of controversy, and unmet needs, and we suggest what studies should be performed moving forward.

Management of Allergic Skin Disorders in Pregnancy

The safe management of allergic skin disorders during pregnancy is essential to maternal and fetal health. Poorly controlled allergic skin disease affects the health of mother and child. This article reviews the disease course and treatment of atopic dermatitis, chronic urticaria, and allergic contact dermatitis in pregnancy. It focuses on topical and systemic therapies in the context of pregnancy and breastfeeding. Because disease activity may vary in pregnancy, prescription stewardship is imperative; a balance among disease control, minimum effective dosing, and medication safety profiles should be maintained. Secondary complications and risks to maternal or infant health should also be avoided.

Chronic spontaneous urticaria: Focus on pathophysiology to unlock treatment advances

Chronic spontaneous urticaria (CSU) is a debilitating skin disease characterized by intensely itchy wheals, angioedema, or both. Symptoms recur spontaneously, on a near-daily basis, over >6 weeks; many patients experience flare-ups over several years and, consequently, reduced quality of life. Differences between the inflammatory profiles of the skin of CSU patients (wheals and nonlesional sites) and healthy controls indicate that key drivers such as mast cells, eosinophils, and basophils interact, release vasoactive mediators, and prime the skin, leaving patients predisposed to symptoms. Many cytokines and chemokines involved in these inflammatory networks and their corresponding intracellular signaling cascades have been identified. These insights informed the development of therapies such as omalizumab, dupilumab, and Bruton's tyrosine kinase (BTK) inhibitors, marking a renewed focus on pathogenesis in CSU clinical research. Despite progress, current therapies provide symptomatic control but do not appear to redress the inflammatory balance in the skin permanently. A deeper understanding of CSU pathogenesis will permit a more targeted approach to developing novel treatments with curative intent. Here, we review what is known about the pathogenesis of CSU and consider how this can be used to identify rational targets to improve patient care further.

IgG and IgE Autoantibodies to IgE Receptors in Chronic Spontaneous Urticaria and Their Role in the Response to Omalizumab

Background: Chronic spontaneous urticaria (CSU) is defined as the recurrence of unprovoked transient wheals and itch for more than 6 weeks. Currently, there is an unmet need concerning response prediction in CSU. The present study investigated biomarkers of type I and type IIb autoimmunity as potential predictors of response to omalizumab in CSU. Materials and methods: Differences in levels of IgG and IgE autoantibodies targeting the high- and low-affinity IgE receptors (FcεRI and FcεRII, respectively), as well as spontaneous and specifically triggered leukotriene C (LTC)4 release by basophils from the investigated subjects, were evaluated in 18 consecutive, prospectively enrolled CSU patients and 18 age- and sex-matched, healthy non-atopic controls. Results: The patients with CSU had higher levels of anti-FcεRI IgE (542 (386.25-776.5) vs. 375 (355-418), optical density (OD), p = 0.008), and IgG (297 (214.5-431.25) vs. 193.5 (118-275) OD, p = 0.004) autoantibodies relative to the controls. Simultaneous anti-FcεRI IgG and IgE positivity (i.e., both autoantibody levels above the respective cut-offs) was recorded only in late- and non-responders (3/8 and 1/2, respectively). Discussion: Significantly higher anti-FcεRI IgE autoantibody levels were found in the CSU patients as compared to the controls, supporting FcεRI as an autoallergic target of IgE (autoallergen) in the complex pathophysiological scenario of CSU. The co-occurrence of anti-FcεRI IgG and IgE autoantibodies was documented only in late- and non-responders, but not in early ones, crediting the co-existence of autoimmune and autoallergic mechanisms as a driver of late/poor response to omalizumab.

Potential contribution of Helicobacter pylori proteins in the pathogenesis of type 1 gastric neuroendocrine tumor and urticaria. In silico approach

BACKGROUND

Helicobacter pylori has been linked to several diseases such as chronic urticaria, gastritis, and type 1 gastric neuroendocrine tumors (type 1 gNET). Although these diseases seem to have different mechanisms, their relationship with H. pylori suggests a common inflammatory pathway.

OBJECTIVE

To identify potential cross-reactive antigens between H. pylori and humans involved in chronic urticaria and type 1 gNET.

METHODS

Alignment was carried out among human proteins associated with urticaria (9 proteins), type 1 gNET (32 proteins), and H. pylori proteome. We performed pairwise alignment among the human and H. pylori antigens with PSI-BLAST. Modeling based on homology was done with the Swiss model server and epitope prediction with the Ellipro server. Epitopes were located on a 3D model using PYMOL software.

RESULTS

The highest conserved sequence was found between the human HSP 60 antigen and the H. pylori chaperonin GroEL with an identity of 54% and a cover of 92%, followed by the alpha and gamma enolases and two H. pylori phosphopyruvate hydratase, both with an identity and cover of 48% and 96%, respectively. The H/K ATPase (Chain A) showed high identity with two H. pylori proteins (35.21% with both P-type ATPase), but with low cover (only 6%). We observed eight linear and three discontinuous epitopes for human HSP 60 and three lineal and one discontinuous epitope for both alpha-enolase and gamma enolase, high conserved with H. pylori sequences.

CONCLUSION

Some type 1 gNET antigens shared potential cross-reactive epitopes with H. pylori proteins, suggesting that molecular mimicry could be a mechanism that explains the relationship between the infection and this disease. Studies evaluating the functional impact of this relationship are needed.

Biologics for chronic spontaneous urticaria: toward a personalized treatment

INTRODUCTION

Chronic spontaneous urticaria (CSU) is characterized by the recurrent occurrence of short-lived wheals with or without angioedema for more than 6 weeks. Although its pathogenesis is not completely defined, several mechanisms seem involved, including autoimmunity and autoallergy with complement and coagulation activation. Various biologics are currently available or under investigation to counteract different CSU pathomechanisms.

AREAS COVERED

The recent literature dealing with biologics in the treatment of CSU was screened and analyzed; the different treatments were divided into anti-IgE and other than anti-IgE biologics. The latter were subdivided according to their target mechanisms.

EXPERT OPINION

Biologic drugs exert their effects in a very precise and specific manner. A majority of patients (arguably those with type I disease) respond to anti-IgE treatment. Others, possibly with type IIa disease, show a slow response to anti-IgE drugs. Things are much more complicated in anti-IgE-refractory patients. Some respond well to nonspecific immune suppressors, such as corticosteroids and cyclosporin suggesting that an immune-mediated pathogenic mechanism, not involving the high-affinity IgE receptor, is probably active. Several ongoing studies are evaluating biologics and small molecules counteracting other pathomechanisms, including anti-receptor biologics, Bruton tyrosine kinase (BTK) inhibitors, mast cell targets, and specific cytokines.

Remibrutinib, a novel BTK inhibitor, demonstrates promising efficacy and safety in chronic spontaneous urticaria

BACKGROUND

Chronic spontaneous urticaria (CSU) is inadequately controlled in many patients and greatly affects quality of life. Remibrutinib, a highly selective, oral, novel covalent Bruton tyrosine kinase inhibitor, might be effective in CSU.

OBJECTIVE

This first-in-patient trial aimed to evaluate the efficacy and safety of remibrutinib in CSU treatment and characterize the dose-response.

METHODS

This randomized, double-blind, placebo-controlled, phase 2b dose-finding trial evaluated remibrutinib (12 weeks) in patients inadequately controlled with second-generation H₁-antihistamines, with at least moderately active CSU, with or without prior anti-IgE treatment (NCT03926611). Patients received remibrutinib 10 mg once daily, 35 mg once daily, 100 mg once daily, 10 mg twice daily, 25 mg twice daily, 100 mg twice daily, or placebo (1:1:1:1:1:1:1 ratio). The main end points were weekly Urticaria Activity Score change from baseline at week 4 and safety.

RESULTS

Overall, 311 patients were randomized. Reduced symptom score was observed for all remibrutinib doses from week 1 until week 12, with weekly Urticaria Activity Score change from baseline at week 4: -19.1 (10 mg once daily), -19.1 (35 mg once daily), -14.7 (100 mg once daily), -16.0 (10 mg twice daily), -20.0 (25 mg twice daily), -18.1 (100 mg twice daily), and -5.4 for placebo (nominal P < .0001 for all doses vs placebo). Most adverse events were mild or moderate, with no dose-dependent pattern.

CONCLUSION

Remibrutinib was highly effective in the treatment of CSU over the entire dose range, with a rapid onset of action and a favorable safety profile.

Comorbidities of Chronic Urticaria: A glimpse into a complex relationship

Chronic Urticaria (CU) is a chronic inflammatory, predominantly mast cell-driven disease, characterized by the development of wheals and/or angioedema for more than 6 weeks. It affects approximately 1%-5% of the total population worldwide and imposes a substantial burden on health-related quality of life, significantly affecting patients' daily life. The economic impact on the health system is also not negligible, with an estimated cost per patient per year of approximately 2.000 $ in the United States. Although the underlying pathophysiology is not fully explored, autoimmune mechanisms have been proposed, including type I ("autoallergy" by means of autoantibodies to self-antigens) and type IIb (autoimmunity). Atopic, autoimmune, and psychiatric disorders are prevalent comorbidities in both children and adults with Chronic Spontaneous Urticaria (CSU). Although malignancies, cardiovascular diseases and other comorbidities have also been reported as associated diseases in patients with CSU, data remain scarce. It is still unknown whether the aforementioned comorbidities share common pathophysiological mechanisms with specific endotypes of CSU. The current review aims to overview current data on comorbidities of CU, and furthermore to comment on the potential linked pathways underlying these diseases.

Cumulative IgE-levels specific for respiratory allergens as biomarker to predict efficacy of anti-IgE-based treatment of severe asthma

Molecular therapies, including anti-IgE, biologicals and small molecules are increasingly used for treatment of asthma. The effectiveness of these therapies may be increased with biomarkers. Aim of this study was to assess the value of measuring cumulative IgE levels specific for respiratory allergens to increase the efficacy of anti-IgE therapy for severe bronchial asthma. One hundred and thirty seven patients with severe asthma were recruited from 2016 to 2022. Standard empirical allergy diagnosis (i.e., anamnesis, skin testing, allergen-specific IgE measurement), blood eosinophil counting, measurement of total IgE and of cumulative IgE-specific for respiratory allergens by Phadiatop™ were performed. Thirty four patients with severe allergic asthma, for whom all three diagnostic methods were performed, were then used to analyze the efficacy of anti-IgE treatment in patients stratified in two groups according to cumulative IgE levels specific for respiratory allergens determined by Phadiatop™. Group #1 patients (n = 8) had cumulative specific IgE values ≥ 0.35 and < 1.53 PAU/l while in group #2 patients (n = 26) they were ≥ 1.53 PAU/l. Treatment with Omalizumab was performed for at least 12 months. The level of asthma control (ACT questionnaire), the number of asthma exacerbations, the quality of life (AQLQ questionnaire), the need for systemic corticosteroids, and the respiratory function (FEV1) was determined by “before-after” analysis for each group, followed by a comparison of the dynamics between groups. In group 2 patients with an initial allergen-specific IgE level ≥ 1.53 kUA/L, the efficacy of Omalizumab treatment was better regarding asthma control, number of exacerbations, and quality of life than in group 1 patients. Our study provides evidence that measuring cumulative levels of IgE specific for respiratory allergens could be a useful screening method for detecting an allergic phenotype of severe asthma and may serve as biomarker to enhance the success of IgE-targeted therapy.

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.

Omalizumab versus cyclosporin-A for the treatment of chronic spontaneous urticaria: can we define better-responding endotypes?

Background

Chronic Spontaneous Urticaria (CSU) is characterized by recurrent wheals and/or angioedema for longer than 6-weeks. Guidelines recommend Omalizumab (Oma) as first-line and Cyclosporine-A (Cs-A) as second-line treatment in antihistamine resistant CSU. This step-wise algorithm might be time-consuming and costly.

Objective

To determine indicators of response to Oma or Cs-A in CSU patients.

Methods

We retrospectively analyzed data from seven centers in Turkey; the inclusion criteria for patients were to receive both Oma and Cs-A treatment (not concurrently) at some point in time during their follow-up. Clinical and laboratory features were compared between groups.

Results

Among 110 CSU patients; 47 (42.7%) were Oma-responders, 15 (13.6%) were Cs-A-responders, and 24 (21.8%) were both Oma and Cs-A responders and 24 (21.8%) were non-responders to either drug. High CRP levels were more frequent in Cs-A-responders (72.7% vs. 40.3%; p = 0.055). Oma-responders had higher baseline UCT (Urticaria Control Test) scores (6 vs. 4.5; p = 0.045). Responders to both drugs had less angioedema and higher baseline UCT scores compared to other groups (33.3% vs. 62.8%; p = 0.01 and 8 vs. 5; p = 0.017). Non-responders to both drugs had an increased frequency in the female gender and lower baseline UCT scores compared to other groups (87.5% vs. 61.6%; p = 0.017 and 5 vs. 7; p = 0.06).

Study Limitations

Retrospective nature, limited number of patients, no control group, the lack of the basophil activation (BAT) or BHRA (basophil histamine release assay) tests.

Conclusions

Baseline disease activity assessment, which considers the presence of angioedema and disease activity scores, gender, and CRP levels might be helpful to predict treatment outcomes in CSU patients and to choose the right treatment for each patient. Categorizing patients into particular endotypes could provide treatment optimization and increase treatment success.

Autoimmune chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is a debilitating mast cell-driven disease characterized by recurrent wheals and/or angioedema. Substantial progress has been made in dissecting the 2 main autoimmune mechanisms that drive the pathogenesis of CSU. Type I autoimmune (autoallergic) CSU is associated with IgE antibodies against autoantigens, for example, thyroid peroxidase and IL-24. Type IIb autoimmune CSU is mediated by autoantibodies that activate mast cells, for example, via IgE and FcεRI, and is present in less than 10% of patients with CSU when strict criteria are used, that is, triple positivity of autologous serum skin test, immunoassays for IgG autoantibodies, and basophil activation tests. A subpopulation of patients with CSU has both types. Type IIb autoimmune CSU is characterized by higher disease severity, concomitant autoimmune diseases, low levels of total IgE, elevated levels of IgG-anti-thyroid peroxidase, basopenia, eosinopenia, poor response to antihistamines and to omalizumab, and a good response to cyclosporine. Novel targeted therapies for CSU are under development such as ligelizumab, an anti-IgE, fenebrutinib and remibrutinib, Bruton's tyrosine kinase inhibitors, and dupilumab, an anti-IL-4Rα. Further studies should investigate the overlap between autoallergic and type IIb autoimmune CSU, optimize the diagnosis of both autoimmune endotypes using easy-to-perform, noninvasive, and inexpensive markers, and assess differences in response to therapy.

The Role of Crosstalk of Immune Cells in Pathogenesis of Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is defined as recurrent episodes of spontaneous wheal development and/or angioedema for more than six weeks and at least twice a week. The core link in the pathogenesis of CSU is the activation of mast cells, T cells, eosinophils, and other immune cells infiltrating around the small venules of the lesion. Increased vascular permeability, vasodilatation, and recruitment of inflammatory cells directly depend on mast cell mediators’ release. Complex regulatory systems tightly influence the critical roles of mast cells in the local microenvironment. The bias toward Th2 inflammation and autoantibodies derived from B cells, histamine expressed by basophils, and initiation of the extrinsic coagulation pathway by eosinophils or monocytes exerts powerful modulatory influences on mast cells. Cell-to-cell interactions between mast cells and eosinophils/T cells also are regulators of their function and may involve CSU’s pathomechanism. This review summarizes up-to-date knowledge regarding the crosstalk between mast cells and other immune cells, providing the impetus to develop new research concepts and treatment strategies for CSU.

Role of Basophils in a Broad Spectrum of Disorders

Basophils are the rarest granulocytes and have long been overlooked in immunological research due to their rarity and similarities with tissue-resident mast cells. In the last two decades, non-redundant functions of basophils have been clarified or implicated in a broad spectrum of immune responses, particularly by virtue of the development of novel analytical tools for basophils. Basophils infiltrate inflamed tissues of patients with various disorders, even though they circulate in the bloodstream under homeostatic conditions. Depletion of basophils results in the amelioration or exaggeration of inflammation, depending on models of disease, indicating basophils can play either beneficial or deleterious roles in a context-dependent manner. In this review, we summarize the recent findings of basophil pathophysiology under various conditions in mice and humans, including allergy, autoimmunity, tumors, tissue repair, fibrosis, and COVID-19. Further mechanistic studies on basophil biology could lead to the identification of novel biomarkers or therapeutic targets in a broad range of diseases.

Urticarial vasculitis: Clinical and laboratory findings with a particular emphasis on differential diagnosis

Urticarial vasculitis (UV) is a rare cutaneous vasculitis of small vessels characterized by recurrent episodes of wheal-like lesions that tend to last more than 24 hours, healing with a residual ecchymotic postinflammatory hyperpigmentation. The histopathologic pattern of UV is that of leukocytoclastic vasculitis, consisting of fibrinoid necrosis of dermal vessels' walls and neutrophil-rich perivascular inflammatory infiltrates. Although its etiopahogenesis remains still undefined, UV is now regarded as an immune complex-driven disease with activation of the complement cascade, leading to exaggerated production of anaphylatoxins that are responsible for neutrophil recruitment and activation. This condition can be categorized into 2 main entities according to serum complement levels: normocomplementemic UV and hypocomplementemic UV, the latter being associated with circulating anti-C1q autoantibodies and possible extracutaneous manifestations. Systemic multiorgan involvement may be seen particularly in syndromic hypocomplementemic UV, also known as McDuffie syndrome. This review summarizes the clinicopathological and laboratory features as well as the underlying pathophysiological mechanisms of UV. A focus on its main differential diagnoses is provided, that is, chronic spontaneous urticaria, bullous pemphigoid, IgA (Henoch-Schönlein purpura) and IgM/IgG immune complex vasculitis, lupus erythematous tumidus, Wells syndrome, erythema multiforme, cutaneous mastocytosis, cryopyrin-associated periodic syndromes, and coronavirus disease 2019-associated and anti-severe acute respiratory syndrome coronavirus 2-vaccine-associated urticarial eruptions.

A novel detection method for cross-linking of IgE-receptors by autoantibodies in chronic spontaneous urticaria

BACKGROUND

Autoantibodies (AAbs) against immunoglobulin E (IgE) antibodies (Abs) and their high-affinity receptor alpha subunits (FcεRIα) are key factors in the elicitation of type IIb autoimmune chronic spontaneous urticaria (type IIb aiCSU). In this study, we aimed to develop a new method to detect functional anti-FcεRIα and anti-IgE AAbs, which can crosslink the plural FcεRІα molecules and IgE Abs on the surface of mast cells and basophils, in sera from aiCSU patients using the amplified luminescence proximity homogeneous assay (Alpha).

METHODS

Sera were obtained from 14 aiCSU patients, as diagnosed by recurrent chronic spontaneous urticaria episodes and positive results for the autologous serum skin test and/or histamine release test (HRT). The AAbs to FcεRIα and IgE Abs were determined in sera from aiCSU patients using enzyme-linked immunosorbent assay (ELISA) and Alpha by cross-linking (AlphaCL) of IgE Abs and/or FcεRІα.

RESULTS

Serum anti-FcεRIα and anti-IgE AAb levels were not significantly different between aiCSU patients and healthy subjects in ELISA. Anti-FcεRIα AAbs were detected in 10 of 14 aiCSU patients who displayed positive (5/5) and negative (5/9) results in the HRT for anti-FcεRIα AAbs by AlphaCL, whereas no signals were observed in healthy subjects. Additionally, anti-IgE AAbs were detected in two of four aiCSU patients who displayed positive results in the HRT for anti-IgE AAbs.

CONCLUSIONS

A new assay method using AlphaCL can detect anti-FcεRIα and anti-IgE AAbs with FcεRIα- and IgE-crosslinking abilities in sera from aiCSU patients. This simple and practical assay method may be available as a diagnostic tool for urticaria patients.

EAACI Biologicals Guidelines-Omalizumab for the treatment of chronic spontaneous urticaria in adults and in the paediatric population 12-17 years old

Chronic spontaneous urticaria (CSU) imposes a significant burden on patients, families and healthcare systems. Management is difficult, due to disease heterogeneity and insufficient efficacy of classical drugs such as H₁ R-antihistamines. Better understanding of the mechanisms has enabled a stratified approach to the management of CSU, supporting the use of targeted treatment with omalizumab. However, many practical issues including selection of responders, the definition of response, strategies to enhance the responder rate, the duration of treatment and its regimen (in the clinic or home-based) and its cost-effectiveness still require further clarification. The EAACI Guidelines on the use of omalizumab in CSU follow the GRADE approach in formulating recommendations for each outcome. In addition, future therapeutic approaches and perspectives as well as research priorities are discussed.

Effects of pregnancy on chronic urticaria: Results of the PREG-CU UCARE study

BACKGROUND

Chronic urticaria (CU) predominantly affects women, and sex hormones can modulate disease activity in female CU patients. As of now, the impact of pregnancy on CU is largely unknown.

AIM

To analyze the course and features of CU during and after pregnancy.

PATIENTS AND METHODS

PREG-CU is an international, multicenter study of the Urticaria Centers of Reference and Excellence (UCARE) network. Data were collected via a 47-item questionnaire completed by CU patients, who became pregnant within the last 3 years.

RESULTS

A total of 288 pregnancies of 288 CU patients from 13 countries were analyzed (mean age at pregnancy: 32.1 ± 6.1 years, duration of CU: 84.9 ± 74.5 months; CSU 66.9%, CSU + CIndU 20.3%, CIndU 12.8%).During pregnancy, 51.1% of patients rated their CU as improved, 28.9% as worse, and 20.0% as unchanged.CU exacerbations most commonly occurred exclusively during the third trimester (in 34 of 124 patients; 27.6%) or the first (28 of 124; 22.8%). The risk factors for worsening of CU during pregnancy were having mild disease and no angioedema before pregnancy, not taking treatment before pregnancy, CIndU, CU worsening during a previous pregnancy, treatment during pregnancy, and stress as a driver of exacerbations. After giving birth, urticaria disease activity remained unchanged in 43.8% of CU patients, whereas 37.4% and 18.1% experienced worsening and improvement, respectively.

CONCLUSIONS

These results demonstrate the complex impact of pregnancy on the course of CU and help to better counsel patients who want to become pregnant and to manage CU during pregnancy.

The Role of Coagulation and Complement Factors for Mast Cell Activation in the Pathogenesis of Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is a common skin disorder characterized by an almost daily recurrence of wheal and flare with itch for more than 6 weeks, in association with the release of stored inflammatory mediators, such as histamine, from skin mast cells and/or peripheral basophils. The involvement of the extrinsic coagulation cascade triggered by tissue factor (TF) and complement factors, such as C3a and C5a, has been implied in the pathogenesis of CSU. However, it has been unclear how the TF-triggered coagulation pathway and complement factors induce the activation of skin mast cells and peripheral basophils in patients with CSU. In this review, we focus on the role of vascular endothelial cells, leukocytes, extrinsic coagulation factors and complement components on TF-induced activation of skin mast cells and peripheral basophils followed by the edema formation clinically recognized as urticaria. These findings suggest that medications targeting activated coagulation factors and/or complement components may represent new and effective treatments for patients with severe and refractory CSU.

Systemic and local evidence for complement involvement in chronic spontaneous urticaria

Background

The pathogenesis of chronic spontaneous urticaria (CSU), including the mechanism of action of omalizumab, remain unclear. We hypothesized complement system involvement given the often fast clinical response induced by treatment, including omalizumab. Therefore, we assessed the role of various complement factors surrounding omalizumab treatment.

Methods

Thirty CSU patients (median age 42 [range 21-70]; 73 % female) with a median once daily Urticaria Activity Score over 7 days (UAS7) score at baseline of 31.5 points were enrolled. Treatment consisted of six administrations of 300 mg omalizumab every 4 weeks succeeded by a follow-up period of 12 weeks. Four punch skin biopsies were taken per patient; at baseline from lesional skin, at baseline from nonlesional skin, and after 1 and 7 days from formerly lesional skin. Complement activity, including C1q, C3, C3bc/C3, C4, C4bc/C4, C5a, and Membrane Attack Complex in peripheral blood were analyzed and complement activation in the skin was determined by the analysis of C4d deposition. Results were related to the clinical response to omalizumab.

Results

Fifteen patients showed a UAS7 score of 6 or lower (median 0) at Week 24, 15 patients did not (median 16). Lesional skin biopsies at baseline revealed complement deposition (C4d) in blood vessels in the papillary dermis of 53% (16/30) of the patients, which suggests involvement of immune complexes in the pathogenesis of urticaria. Moreover, indication of increased complement activation in CSU was substantiated by increased C5a levels in peripheral blood compared to healthy controls (p = 0.010). The clinical effect of omalizumab could not be linked to the variation of complement components.

Conclusions

Both C4d deposition in lesional skin and elevated C5a levels in peripheral blood indicate the involvement of complement activation in the pathogenesis of CSU. No correlation was found between omalizumab and activation of complement indicative of independent processes in the immunopathogenesis of CSU.

The Diagnostic Workup in Chronic Spontaneous Urticaria-What to Test and Why

BACKGROUND

In chronic spontaneous urticaria (CSU), the guidelines recommend very limited diagnostic procedures during the routine workup, although additional investigations might be indicated in some patients with CSU. For physicians treating patients with CSU, it is often difficult to decide which diagnostic tests are useful.

OBJECTIVE

To provide recommendations on what diagnostic tests should be performed on which patients with CSU.

METHODS

We performed an extensive literature search on the respective topics and identified relevant questions that should prompt diagnostic procedures based on the published evidence and expert consensus among all authors.

RESULTS

We provide questions, diagnostic testing, where appropriate, and recommendation that should be included when assessing the history of a patient with CSU, to explore and rule out differential diagnoses, to assess patients for underlying causes and modifying conditions, to explore patients for comorbid diseases and consequences of having CSU, and to assess patients for CSU components that can help to predict their disease course and response to treatment.

CONCLUSIONS

Here, we provide physicians treating patients with CSU with information about which clues should lead to which tests and why.

The Pathogenesis of Chronic Spontaneous Urticaria: The Role of Infiltrating Cells

Chronic spontaneous urticaria is characterized by a perivascular non-necrotizing cellular infiltrate around small venules of the skin. It consists primarily of CD4(+) lymphocytes, a prominence of the T helper (Th)2 subtype but also Th1 cells, with Th17 cell-derived cytokines elevated in plasma. There are also neutrophils, eosinophils, basophils, and monocytes. Chemokines derived from mast cells and activated endothelial cells drive the process. Although the role of the cellular infiltrate has not previously been addressed, each constituent can contribute to the overall pathogenesis. It is of interest that CSU responds to corticosteroid, yet, short-term steroids do not affect autoimmunity or degranulation of mast cells, and act on margination of cells along the endothelium and chemotaxis to enter the surrounding dermis. In this review, we address each cell's contribution to the overall inflammatory response, as it is currently understood, with a view toward development of therapeutic options that impede the function of critical cells and/or their secretory products.

Non-IgE-mediated anaphylaxis

Anaphylaxis is a rapidly evolving, acute, life-threatening reaction that occurs rapidly on contact with a trigger. Anaphylaxis is classically defined as an allergen-driven process that induces specific IgE and the activation of mast cells and basophils through the cross-linking of IgE receptors. However, it is clear that non-IgE-mediated pathways can induce symptoms indistinguishable from those of classic anaphylaxis, and their activation could explain the severity of IgE-mediated anaphylaxis. Indeed, mast cells and basophils can be activated by antibodies against IgE or their receptors, by molecules such as anaphylatoxins, or through G-coupled receptors. Some other allergens can induce antibodies of class IgG that can activate neutrophils to produce a molecule similar to histamine to induce anaphylaxis. Finally, some inflammatory mediators such as bradykinin or prostaglandin can also modulate mast cell and basophil activation as well as directly cause vasodilation and bronchoconstriction, resulting in anaphylaxis-like reactions.

Management of Pediatric Chronic Spontaneous Urticaria: A Review of Current Evidence and Guidelines

Chronic urticaria (CU) is associated with debilitating symptoms such as pruritic wheals and/or angioedema, which can significantly affect patients’ sleep, productivity and quality of life. Chronic spontaneous urticaria (CSU) is defined in cases in which no triggering factor is identified. Various guidelines directing the optimal management of CU in the adult population were published and updated over the recent years with the most accepted and widely used being the EAACI/GA²LEN/EDF/WAO 2017 guidelines. Meanwhile, guidelines specific to the pediatric population are scarce, mainly due to the fact that high quality evidence is lacking for many treatment options in this age group. The objective of this article is to review and synthesize the existing literature regarding the management of pediatric CSU. Our review highlights evidence supporting the EAACI/GA²LEN/EDF/WAO 2017 treatment guidelines with non-sedating second-generation antihistamines (sgAHs) as the mainstay of treatment for pediatric CSU, considering their demonstrated efficacy and reassuring safety profile. Additionally, the use of omalizumab in adolescents is well supported by the current literature. There is limited data available regarding the updosing of sgAHs, omalizumab in children with CSU under 12 years of age and the treatment with cyclosporine and leukotriene receptor antagonists (LTRAs) in pediatric patients of all ages. However, the results from currently available case series and case reports are promising for omalizumab and cyclosporine use in children with CSU, although large and well-designed randomized control trials (RCTs) assessing these treatment options are needed in order to formulate strong recommendations for their use. First-generation antihistamines (fgAHs) remain commonly used in pediatric CSU treatment despite a lack of studies assessing their efficacy and safety in the pediatric population and their widely known inferior safety profile compared to sgAHs.

Biomarkers of chronic spontaneous urticaria and their clinical implications

Introduction: Chronic spontaneous urticaria (CSU) is a frequent disorder in which activation of effector cells and histamine release can be induced via several distinct pathogenetic mechanisms. Much work has been carried out to identify biomarkers useful for classifying CSU patients, and to predict their response to currently available treatments.Areas covered: The recent literature dealing with CSU biomarkers was screened in PubMed and Google Scholar using 'chronic spontaneous urticaria', 'biomarker', 'diagnosis', 'therapy' and 'treatment response' as key words. The characteristics found in relevant papers were divided into clinical and serological biomarkers of (a) clinical severity/disease activity, and (b) response to treatments.Expert opinion: A diagnostic biomarker for CSU is still missing. Most biomarkers described so far do not seem to possess sufficient specificity for this disease. Basopenia and the activation of the coagulation cascade might be biomarkers of disease activity and severity, but information available so far is insufficient to consider their routine use. Markers suggesting IgG-mediated autoimmunity (autologous serum skin test, basophil activation/histamine release assays, low total IgE) seem to identify patients less prone to respond to omalizumab but responsive to cyclosporine. In contrast, 'autoallergy' (i.e. the presence of IgE to autoallergens), which is often associated with elevated IgE levels seems to identify patients who will respond to omalizumab.

Fenebrutinib in H1 antihistamine-refractory chronic spontaneous urticaria: a randomized phase 2 trial

Bruton's tyrosine kinase (BTK) is crucial for FcεRI-mediated mast cell activation and essential for autoantibody production by B cells in chronic spontaneous urticaria (CSU). Fenebrutinib, an orally administered, potent, highly selective, reversible BTK inhibitor, may be effective in CSU. This double-blind, placebo-controlled, phase 2 trial (EudraCT ID 2016-004624-35 ) randomized 93 adults with antihistamine-refractory CSU to 50 mg daily, 150 mg daily and 200 mg twice daily of fenebrutinib or placebo for 8 weeks. The primary end point was change from baseline in urticaria activity score over 7 d (UAS7) at week 8. Secondary end points were the change from baseline in UAS7 at week 4 and the proportion of patients well-controlled (UAS7 ≤ 6) at week 8. Fenebrutinib efficacy in patients with type IIb autoimmunity and effects on IgG-anti-FcεRI were exploratory end points. Safety was also evaluated. The primary end point was met, with dose-dependent improvements in UAS7 at week 8 occurring at 200 mg twice daily and 150 mg daily, but not at 50 mg daily of fenebrutinib versus placebo. Asymptomatic, reversible grade 2 and 3 liver transaminase elevations occurred in the fenebrutinib 150 mg daily and 200 mg twice daily groups (2 patients each). Fenebrutinib diminished disease activity in patients with antihistamine-refractory CSU, including more patients with refractory type IIb autoimmunity. These results support the potential use of BTK inhibition in antihistamine-refractory CSU.

Autoimmune Diseases Are Linked to Type IIb Autoimmune Chronic Spontaneous Urticaria

PURPOSE

Patients with chronic spontaneous urticaria (CSU) have an increased risk for comorbid autoimmune diseases. In this retrospective multicenter study of CSU patients, we evaluated clinical and laboratory features of CSU associated with a higher risk of comorbid autoimmune diseases.

METHODS

We analyzed records of CSU patients (n = 1,199) for a history or presence of autoimmune diseases. Patients were diagnosed with type IIb autoimmune CSU (aiCSU) if all 3 tests were positive: autologous serum skin test (ASST), basophil histamine release assay (BHRA) and/or basophil activation test (BAT), and IgG autoantibodies against FcεRIα/IgE detected by immunoassay.

RESULTS

Twenty-eight percent of CSU patients had at least 1 autoimmune disease. The most prevalent autoimmune diseases were Hashimoto's thyroiditis (HT) (≥ 21%) and vitiligo (2%). Two percent of CSU patients had ≥ 2 autoimmune diseases, most frequently HT plus vitiligo. Comorbid autoimmune diseases, in patients with CSU, were associated with female sex, a family history of autoimmune diseases, and higher rates of hypothyroidism and hyperthyroidism (P < 0.001). Presence of autoimmune diseases was linked to aiCSU (P = 0.02). The risks of having autoimmune diseases were 1.7, 2.9 and 3.3 times higher for CSU patients with a positive ASST, BHRA and BAT, respectively. In CSU patients, markers for autoimmune diseases, antinuclear antibodies and/or IgG anti-thyroid antibodies were associated with non-response to omalizumab treatment (P = 0.013).

CONCLUSIONS

In CSU, autoimmune diseases are common and linked to type IIb autoimmune CSU. Our results suggest that physicians assess and monitor all adult patients with CSU for signs and symptoms of common autoimmune diseases, especially HT and vitiligo.

Presence of positive skin prick tests to inhalant allergens and markers of T2 inflammation in subjects with chronic spontaneous urticaria (CSU): a systematic literature review

BACKGROUND

Current guidelines do not recommend performing aeroallergen skin prick testing (SPT) in chronic spontaneous urticaria (CSU).

OBJECTIVE

The objective of this review was to investigate the presence of aeroallergen sensitization and markers of T2 inflammation in subjects with CSU.

METHODS

Systematic literature reviews to identify all studies that evaluated the presence of T2 markers of allergic inflammation in CSU subjects were performed.

RESULTS

In 16 studies that assessed the prevalence of positive SPT to multiple aeroallergens in CSU, 38.5% of CSU subjects had positive SPT. In three controlled studies, 34.2% of CSU subjects had positive SPT to multiple aeroallergens, compared to 13.6% of controls (p = 0.047). In 18 studies that assessed the prevalence of house dust mite (HDM) positive SPT in CSU, 27.5% of CSU subjects had positive SPT. In three controlled studies, 27.5% of CSU subjects had positive SPT to HDM, compared to 2.1% of controls (p = 0.047). Overall, CSU subjects were 3.1 times more likely to be aeroallergen-sensitized (95% CI 1.7-5.8, p = 0.0002) and 6.1 times more likely to be HDM-sensitized (95% CI 3.7-9.9, p < 0.00001) than controls. Mean total serum IgE (tIgE) levels were 238 kU/L and median tIgE levels were 164 kU/L, which was greater than the upper 90th percentile of normal (< 137 kU/L). Compared to healthy controls, CSU subjects were 6.5 times more likely to have IgG autoantibody against FcεR1α (p = 0.001), 2.4 times more likely to have IgG anti-IgE antibody (p = 0.03) and 5 times more likely to have anti-thyroid peroxidase (anti-TPO) antibody (p = 0.02). When corticosteroids were withheld for ≥ 28 days, mean blood eosinophil percentage was elevated at 5.9% (normal < 4%), but other studies reporting absolute count found the mean was in the normal range, 239 × 10 6 / L (normal < 400 × 10 6 / L).

CONCLUSION

Increased aeroallergen sensitization, tIgE, autoantibodies and blood eosinophil percentage in the CSU subjects indicates the possible importance of T2 inflammation in the pathogenesis of CSU. Further studies may be warranted to determine if specific allergen avoidance, desensitization or improvement in the mucosal allergic inflammation present in asthma and/or rhinitis has any benefit in the management of CSU.