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Background: Urticarial vasculitis (UV) should be differentiated from chronic spontaneous urticaria (CSU) in patients initially presenting with recurrent wheals, although criteria for differential diagnosis remain ill-defined., Objectives: To set the goals, define criteria and unmet needs in UV diagnosis and differential diagnosis with CSU, and explore the possibility of coexistence of both diseases., Methods: Thirteen experts experienced in UV research participated in a Delphi survey of European Academy of Allergy and Clinical Immunology taskforce. This Delphi survey involved three rounds of anonymous responses to n = 32 questions with the aim to aggregate the experts' opinions and to achieve consensus. Urticaria specialists (n = 130, most from Urticaria Centers of Reference and Excellence) evaluated the consensus statements and recommendations in the fourth and final round., Results: The panel agreed that essential criteria to guide a skin biopsy in patients with recurrent wheals should include at least one of the following features: wheal duration >24 h, bruising/postinflammatory hyperpigmentation, and systemic symptoms. Leukocytoclasia and fibrin deposits were identified as a minimum set of UV histological criteria. As agreed by the panel members, CSU and normocomplementemic UV (NUV) may coexist in some patients., Conclusions: The use of established criteria for the diagnosis and differential diagnosis of UV in patients with recurrent wheals can help guide the diagnostic approach and prompt earlier treatment. Further studies should investigate whether CSU and NUV are different entities or part of a disease spectrum., (© 2023 The Authors. Clinical and Translational Allergy published by John Wiley & Sons Ltd on behalf of European Academy of Allergy and Clinical Immunology.)

Background: The Angioedema Control Test (AECT) is a patient-reported outcome measure developed and validated for the assessment of disease control in patients with recurrent angioedema. Its sensitivity to change and minimal clinically important difference (MCID) have hitherto not been established., Methods: Patients with recurrent angioedema due to chronic spontaneous urticaria, hereditary angioedema, or acquired C1-inhibitor deficiency were repeatedly asked to complete the AECT along with the Angioedema Quality of Life Questionnaire (AE-QoL), Dermatology Life Quality Index (DLQI), and anchors for disease control and whether treatment was sufficient during routine care visits. The sensitivity to the change of the AECT was determined by correlating changes in its scores over time with changes in the applied anchors. The MCID was determined using anchor-based and distributional criterion-based approaches., Results: Eighty-six cases were used for this analysis. Changes in AECT scores correlated well with AE-QoL changes (but less with changes in the DLQI) as well as other applied anchors, demonstrating its sensitivity to change. The MCID was found to be three points for improvement of angioedema control. The available number of cases with meaningful deterioration in our dataset was too low to reach a definite conclusion on the MCID for deterioration of angioedema control., Conclusion: The AECT is a valuable tool to assess changes in disease control in patients with recurrent angioedema over time. The lowest AECT score change that reflects a meaningful improvement of disease control to patients (MCID) is three points., (© 2023 The Authors. Clinical and Translational Allergy published by John Wiley & Sons Ltd on behalf of European Academy of Allergy and Clinical Immunology.)

Background: Cold urticaria (ColdU) is characterized by pruritic wheals following exposure of the skin to cold. Many patients show insufficient response to antihistamines, the first line treatment. Based on the high efficacy of interleukin-1(IL-1)-inhibition in cold-induced urticarial autoinflammatory diseases, we assessed the effects of rilonacept, an IL-1 inhibitor, in ColdU patients unresponsive to standard treatment., Methods: In this randomized, double-blind, placebo-controlled two-center study, we included 20 patients with ColdU. In the first part, patients received 320 mg rilonacept or placebo (1:1) followed by weekly doses of 160 mg rilonacept or placebo for 6 weeks. In the second part, all patients received weekly 160 mg or 320 mg rilonacept for 6 weeks, open-label. The primary endpoint was change in critical temperature threshold (CTT). Secondary endpoints included changes in quality of life impairment (Dermatology Life Quality Index, DLQI), differences of inflammatory mediators upon cold provocation and safety assessment over the study period., Results: Baseline mean CTTs were 20.2°C (placebo) and 17.3°C (rilonacept). Mean CTTs did not change significantly during the 6-week double-blind treatment (placebo - 0.45°C; rilonacept +0.89°C). IL-6, IL-18 and HSP-70 blood levels showed interindividual variability without significant changes during hand cold water bath provocation in placebo- or rilonacept-treated patients. In contrast, DLQI significantly improved in the rilonacept (mean DLQI reduction of 3.8; p = 0.002) but not in the placebo group (mean DLQI reduction of 0). Comparing baseline with the rilonacept open-label treatment, there were no changes in CTTs or DLQI scores., Conclusion: IL-1 inhibition with rilonacept did not improve ColdU, but demonstrated a good safety profile., Clinical Trial Registration: EudraCT number: 2012-005726-30., Clinicaltrials: gov identifier: NCT02171416., (© 2023 The Authors. Clinical and Translational Allergy published by John Wiley and Sons Ltd on behalf of European Academy of Allergy and Clinical Immunology.)

Chronic urticarial rash, mostly due to chronic spontaneous urticaria (CSU), is seen in up to 1 - 4% of the general population. Urticarial vasculitis (UV) and autoinflammatory syndromes, i.e., cryopyrin-associated periodic syndromes (CAPS) and Schnitzler syndrome (SchS), can mimic CSU-like rash but represent rare disorders with systemic symptoms including fever, headache, conjunctivitis, and arthralgia. Clinical and laboratory features can point to the presence of any of these diseases in patients initially presenting with chronic urticarial rash. These include long-lasting wheals (> 24 hours), lesional burning, systemic symptoms, and/or increase in inflammatory markers (e.g., C-reactive protein, serum amyloid A, and/or S100A8/9). Lesional skin biopsy usually demonstrates leukocytoclastic vasculitis (UV) or neutrophil-rich infiltrate (CAPS and SchS). In contrast to CSU, where second-generation H1 antihistamines and omalizumab allow to control symptoms in most patients, systemic immunosuppression and anti-interleukin (IL)-1 therapies are needed in case of UV and autoinflammatory diseases, respectively. The rarity and low awareness of CSU differential diagnoses may be related to the longer delays in diagnosis and therapy in those affected with UV, CAPS, and SchS. Knowledge of the differential diagnoses of CSU is important because only correct diagnosis allows adequate therapy. Complications such as the development of lymphoproliferative disease in SchS and amyloidosis in CAPS, and the presence of comorbid diseases, such as systemic lupus erythematosus in UV, must be considered and monitored., (© Dustri-Verlag Dr. K. Feistle.)

Somatic mutations in UBA1 cause vacuoles, E1 ubiquitin-activating enzyme, X-linked, autoinflammatory somatic (VEXAS) syndrome, an adult-onset inflammatory disease with an overlap of hematologic manifestations. VEXAS syndrome is characterized by a high mortality rate and significant clinical heterogeneity. We sought to determine independent predictors of survival in VEXAS and to understand the mechanistic basis for these factors. We analyzed 83 patients with somatic pathogenic variants in UBA1 at p.Met41 (p.Met41Leu/Thr/Val), the start codon for translation of the cytoplasmic isoform of UBA1 (UBA1b). Patients with the p.Met41Val genotype were most likely to have an undifferentiated inflammatory syndrome. Multivariate analysis showed ear chondritis was associated with increased survival, whereas transfusion dependence and the p.Met41Val variant were independently associated with decreased survival. Using in vitro models and patient-derived cells, we demonstrate that p.Met41Val variant supports less UBA1b translation than either p.Met41Leu or p.Met41Thr, providing a molecular rationale for decreased survival. In addition, we show that these 3 canonical VEXAS variants produce more UBA1b than any of the 6 other possible single-nucleotide variants within this codon. Finally, we report a patient, clinically diagnosed with VEXAS syndrome, with 2 novel mutations in UBA1 occurring in cis on the same allele. One mutation (c.121 A>T; p.Met41Leu) caused severely reduced translation of UBA1b in a reporter assay, but coexpression with the second mutation (c.119 G>C; p.Gly40Ala) rescued UBA1b levels to those of canonical mutations. We conclude that regulation of residual UBA1b translation is fundamental to the pathogenesis of VEXAS syndrome and contributes to disease prognosis., (© 2022 by The American Society of Hematology.)

Background: Recently, the expression of the mast cell (MC) receptor Mas-related G protein-coupled receptor X2 (MRGPRX2) has been detected in lesional skin of adult patients with cutaneous mastocytosis. As of yet, little is known about the clinical relevance of MRGPRX2 and its agonists in patients with mastocytosis, including indolent systemic mastocytosis (ISM)., Methods: MRGPRX2 and MRGPRX2 agonists, cortistatin (CST), and major basic protein (MBP) were analyzed in lesional and non-lesional skin of patients with ISM and skin of healthy controls by immunohistochemistry. Co-localization of MRGPRX2 and MRGPRX2-mRNA with the MC marker tryptase was assessed by immunofluorescence microscopy and in situ hybridization, respectively. We assessed clinical, demographic, and laboratory data, including mastocytosis activity score (MAS), serum tryptase, and KIT D816V allele burden., Results: The number of MRGPRX2-expressing (MRGPRX2+) cells, MRGPRX2-mRNA+ MCs, and CST-expressing (CST+) and MBP-expressing (MBP+) cells was significantly higher in lesional skin as compared to non-lesional skin and/or skin of healthy controls (all p < 0.05). Increased numbers of MRGPRX2+ cells, MRGPRX2-mRNA+ MCs, and CST+ and MBP+ cells were not associated with clinical and laboratory features of ISM, including disease burden, symptom severity, evidence of anaphylaxis, and tryptase levels., Conclusions: Skin lesions of patients with ISM showed high numbers of MRGPRX2+ cells, although they were not linked to symptom severity. Clinical relevance of the MRGPRX2-mediated pathway of MC activation in ISM remains unclear and should be investigated in further studies., Competing Interests: HB received honoraria (advisory board, speaker) from AbbVie, Novartis, and Sanofi-Aventis, outside of submitted work. JS has no relevant conflict of interest in relation to this work. Outside of it, JS is or recently was advisor for Boehringer Ingelheim. BY is employed by Allakos Inc. MM has no relevant conflict of interest in relation to this work. Outside of it, MM is or recently was a speaker and/or advisor or received institutional research funding from Astria, Allakos, Alnylam, Amgen, Aralez, ArgenX, AstraZeneca, BioCryst, Blueprint, Celldex, Centogene, CSL Behring, Dyax, FAES, Genentech, GIInnovation, GSK, Innate Pharma, Kalvista, Kyowa Kirin, Leo Pharma, Lilly, Menarini, Moxie, Novartis, Pfizer, Pharming, Pharvaris, Roche, Sanofi/Regeneron, Shire/Takeda, Third Harmonic Bio, UCB, and Uriach. FS is or recently was a speaker and/or advisor for and/or has received research funding from Allakos, Blueprint, Celldex, CogentBio, Genentech, Novartis, Moxie, Sanofi/Regeneron, and Uriach. PK has no relevant conflict of interest in relation to this work. Outside of it, PK is or recently was a speaker and/or advisor for Novartis and Roche. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Pyatilova, Ashry, Luo, He, Bonnekoh, Jiao, Moñino-Romero, Hu, Scheffel, Frischbutter, Hermans, Youngblood, Maurer, Siebenhaar and Kolkhir.)

Background: The pathogenesis of contact dermatitis, a common inflammatory skin disease with limited treatment options, is held to be driven by inflammasome activation induced by allergens and irritants. We here aim to identify inflammasome-targeting treatment strategies for irritant contact dermatitis., Methods: A high content screen with 41,184 small molecules was performed using fluorescent Apoptosis associated speck-like protein containing a CARD (ASC) speck formation as a readout for inflammasome activation. Hit compounds were validated for inhibition of interleukin (IL)-1β secretion. Of these, the approved thiuramdisulfide derivative disulfiram was selected and tested in a patch test model of irritant contact dermatitis in 25 healthy volunteers. Topical application of disulfiram, mometasone or vehicle was followed by application of sodiumdodecylsulfate (SDS) for 24 h each. Eczema induction was quantified by mexameter and laser speckle imaging. Corneocyte sampling of lesional skin was performed to assess inflammasome-mediated cytokines IL-1β and IL-18., Results: Disulfiram induced a dose-dependent inhibition of ASC speck formation and IL-1β release in cellular assays in vitro. In vivo, treatment with disulfiram, but not with vehicle and less mometasone, inhibited SDS-induced eczema. This was demonstrated by significantly lower erythema and total perfusion values assessed by mexameter and laser speckle imaging for disulfiram compared to vehicle ( p  < 0.001) and/or mometasone ( p  < 0.001). Also, corneocyte IL-18 levels were significantly reduced after application of disulfiram compared to vehicle ( p  < 0.001)., Conclusion: We show that disulfiram is a dose-dependent inhibitor of inflammasome pathway activation in vitro and inhibitor of SDS-induced eczema in vivo. Topical application of disulfiram represents a potential treatment option for irritant contact dermatitis., Competing Interests: Carolina Vera, Angela Abad‐Perez, Silke Radetzki, Martin Neuenschwander, Edgar Specker, Marc Nazaré, Jens v. Kries, Niklas Amadeus Mahnke, Jörg Scheffel and Stefan Frischbutter have no conflict of interest. Eicke Latz is the co‐founder and consultant to IFM Therapeutics. Hanna Bonnekoh received honoria (advisory board, speaker) from Novartis. Marcus Maurer is or recently was a speaker and/or advisor for and/or has received research funding from Allakos, Alnylam, Amgen, Aralez, ArgenX, AstraZeneca, BioCryst, Blueprint, Celldex, Centogene, CSL Behring, Dyax, FAES, Genentech, GIInnovation, Innate Pharma, Kalvista, Kyowa Kirin, Leo Pharma, Lilly, Menarini, Moxie, Novartis, Pharming, Pharvaris, Roche, Sanofi/Regeneron, Shire/Takeda, ThirdHarmonicBio, UCB, and Uriach. Karoline Krause has received grants from Novartis and Roche and payment for lectures and/or consultancies from Novartis, Roche, and SOBI., (© 2021 The Authors. Clinical and Translational Allergy published by John Wiley & Sons Ltd on behalf of European Academy of Allergy and Clinical Immunology.)

Background: Urticarial vasculitis (UV) is defined by long-lasting urticarial lesions combined with the histopathologic findings of leukocytoclastic vasculitis. As one of the major unmet needs in UV, diagnostic criteria are rather vague and not standardized. Moreover, there seems to be considerable overlap with chronic spontaneous urticaria (CSU), particularly for the normocomplementemic variant of UV. Therefore, this study aimed to develop a diagnostic scoring system that improves the histopathologic discrimination between UV and CSU., Methods: Lesional skin sections of patients with clinical and histopathologic diagnosis of UV (n = 46) and CSU (n = 51) were analyzed (blinded to the diagnosis) for the following pre-defined criteria: presence of leukocytoclasia, erythrocyte extravasation, fibrin deposits, endothelial cell swelling, ectatic vessels, blurred vessel borders, dermal edema, intravascular neutrophil, and eosinophil numbers and numbers of dermal neutrophils, macrophages and mast cells., Results: The greatest differences between UV and CSU samples were observed for leukocytoclasia (present in 76% of UV vs. 3.9% of CSU samples; p < 0.0001), erythrocyte extravasation (present in 41.3% of UV vs. 2.0% of CSU samples; p < 0.0001), and fibrin deposits (present in 27.9% of UV vessels vs. 9.7% of CSU vessels; p < 0.0001). Based on these findings, we developed a diagnostic score, the urticarial vasculitis score (UVS), which correctly assigned 37 of 46 cases of UV and 49 of 51 cases of CSU to the previously established diagnosis., Conclusion: Our results suggest that the UVS, a combined quantitative assessment of the three criteria leukocytoclasia, fibrin deposits and extravasated erythrocytes, distinguishes UV from CSU in skin histopathology. The UVS, if validated in larger patient samples, may help to improve the diagnostic approach to UV., (© 2021 The Authors. Clinical and Translational Allergy published by John Wiley and Sons Ltd on behalf of European Academy of Allergy and Clinical Immunology.)

Background: Urticarial vasculitis (UV) is a rare type of leukocytoclastic vasculitis characterized by long lasting urticarial skin lesions and poor response to treatment. As of yet, no clinical guidelines, diagnostic criteria, or treatment algorithms exist, and the approaches to the diagnostic workup and treatment of UV patients may differ globally. We conducted an online survey to examine how UV patients are diagnosed and treated by international specialists and to reveal the greatest challenges in managing UV patients worldwide., Methods: Distribution of the questionnaire included an email to individuals in the World Allergy Organization (WAO) database, with no restrictions applied to the specialty, affiliation, or nationality of the participants (November 2018). The email contained a link (Internet address) to the online questionnaire. Responses were anonymous. The link to the questionnaire was further sent to the network of Urticaria Centers of Reference and Excellence (UCARE) in the Global Allergy and Asthma European Network (GA 2 LEN) as well as to the Turkish Dermatology Society and the Japanese Society of Allergology, who distributed the link to their members. In addition, the survey link was posted online in the group of the Russian Society of Allergologists and Immunologists., Results: We received 883 completed surveys from physicians in 92 countries. UV was reported to be rare in clinical practice, with an average of 5 patients per physician per year. More than two-thirds of physicians reported wheals, burning of the skin, and residual hyperpigmentation in 60-100% of UV patients. The most frequently reported reason for receiving referrals of patients with UV was to establish the diagnosis. The most important features for establishing the diagnosis of UV were wheals of longer than 24 hours duration (72%), the results of skin biopsy (63%), and post-inflammatory hyperpigmentation (46%). The most common tests ordered in UV patients were complete blood count, erythrocyte sedimentation rate, C-reactive protein, complement components, antinuclear antibodies, and skin biopsy. Physicians considered UV to be of unknown cause in most patients, and drugs and systemic lupus erythematosus to be the most common identifiable causes. Two of 3 physicians reported that they use second-generation antihistamines in standard dose as the first-line therapy in patients with UV. The greatest perceived challenges in the management of UV were the limited efficacy of drugs and the absence of clinical guidelines and treatment algorithms., Conclusions: UV is a challenging disease. Skin biopsy, a gold standard for UV diagnosis, is not performed by many physicians. This may lead to misdiagnosis of UV, for example, as chronic spontaneous urticaria, and to inadequate treatment. International consensus-based recommendations for the classification of UV and the diagnostic workup and treatment, as well as prospective studies evaluating potentially safe and effective drugs for the treatment of UV, are necessary., Competing Interests: The authors declare that they have no relevant conflicts of interest in relation to this work., (© 2020 The Authors.)

Hereditary autoinflammatory diseases are caused by gene mutations of the innate immune pathway, e.g. nucleotide receptor protein 3 (NLRP3). Here, we report a four-generation family with cold-induced urticarial rash, arthralgia, chills, headache and malaise associated with an autosomal-dominant inheritance. Genetic studies identify a substitution mutation in gene F12 (T859A, resulting in p.W268R) which encodes coagulation factor XII (FXII). Functional analysis reveals enhanced autocatalytic cleavage of the mutated protein and spontaneous FXII activation in patient plasma and in supernatant of transfected HEK293 cells expressing recombinant W268R-mutated proteins. Furthermore, we observe reduced plasma prekallikrein, cleaved high molecular weight kininogen and elevated plasma bradykinin. Neutrophils are identified as a local source of FXII. Interleukin-1β (IL-1β) is upregulated in lesional skin and mononuclear donor cells exposed to recombinant mutant proteins. Treatment with icatibant (bradykinin-B2-antagonist) or anakinra (interleukin-1-antagonist) reduces disease activity in patients. In conclusion, our findings provide a link between contact system activation and cytokine-mediated inflammation.

Schnitzler's syndrome is a rare autoinflammatory disorder characterized by interleukin-1ß-mediated and neutrophil-dominated inflammation. Neutrophil extracellular traps (NETs) are web-like structures of decondensed chromatin, histones, and antimicrobial peptides released by neutrophils. NETs were initially described in the context of pathogen defense but are also involved in autoimmune-mediated skin diseases. Here, we assessed the role of neutrophil extracellular trap formation (NETosis) in Schnitzler's syndrome. Immunofluorescence co-staining of myeloperoxidase and subnucleosomal complex was performed on lesional skin samples from patients with Schnitzler's syndrome, other neutrophilic dermatoses (cryopyrin-associated periodic syndrome, Sweet syndrome, and pyoderma gangrenosum), urticarial vasculitis and chronic spontaneous urticaria as well as healthy control skin. Blood neutrophils from patients with Schnitzler's syndrome and controls were isolated, and NETosis was induced by phorbol 12-myristate 13-acetate (PMA). Also, NETosis of control neutrophils induced by symptomatic Schnitzler's syndrome sera, cytokines and sub-threshold PMA doses was studied. Immunofluorescence co-staining revealed widespread and substantial NET formation in lesional skin of Schnitzler's syndrome patients but absence of NETs in chronic spontaneous urticaria and control skin. Neutrophils undergoing NETosis were observed in the skin of other neutrophilic diseases too. Correspondingly, blood neutrophils from Schnitzler's syndrome patients showed significantly elevated NETosis rates compared to control neutrophils following stimulation with PMA. Increased NETosis correlated well with high levels of C-reactive protein (CRP). SchS patients with the lowest NETosis rates had persistent joint and bone pain despite IL-1 blockade. Stimulation of control neutrophils and sub-threshold PMA with sera of symptomatic Schnitzler's syndrome patients disclosed enhanced NETosis as compared to control sera. Our results suggest that the induction of NET formation by neutrophils contributes to skin and systemic inflammation and may support the resolution of local inflammation in Schnitzler's syndrome.