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.

Thyroid Autoimmunity in CSU: A Potential Marker of Omalizumab Response?

The response of severe chronic spontaneous urticaria (CSU) to omalizumab largely depends on the autoimmune or autoallergic endotype of the disease. Whether thyroid autoimmunity may predict omalizumab response along with total IgE in CSU is still unclear. Three hundred and eighty-five patients (M/F 123/262; mean age 49.5 years; range 12-87 years) with severe CSU were studied. Total IgE levels and thyroid autoimmunity (levels of anti-thyroid peroxidase [TPO] IgG) were measured before omalizumab treatment. Based on the clinical response, patients were divided into early (ER), late (LR), partial (PR) and non (NR) responders to omalizumab. Thyroid autoimmunity was detected in 92/385 (24%) patients. Altogether, 52%, 22%, 16% and 10% of patients were ER, LR, PR and NR to omalizumab, respectively. Response to omalizumab was not associated with thyroid autoimmunity (p = 0.77). Conversely, we found a strongly positive association between IgE levels and omalizumab response (p < 0.0001); this association was largely driven by early response (OR = 5.46; 95% CI: 2.23-13.3). Moreover, the predicted probabilities of early response strongly increased with increasing IgE levels. Thyroid autoimmunity alone cannot be used as a clinical predictor of omalizumab response. Total IgE levels remain the only and most reliable prognostic marker for omalizumab response in patients with severe CSU.

IgM Autoantibodies to Complement Factor H in Atypical Hemolytic Uremic Syndrome.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS), a severe thrombotic microangiopathy, is often related to complement dysregulation, but the pathomechanisms remain unknown in at least 30% of patients. Researchers have described autoantibodies to complement factor H of the IgG class in 10% of patients with aHUS but have not reported anti-factor H autoantibodies of the IgM class. METHODS: In 186 patients with thrombotic microangiopathy clinically presented as aHUS, we searched for anti-factor H autoantibodies of the IgM class and those of the IgG and IgA classes. We used immunochromatography to purify anti-factor H IgM autoantibodies and immunoenzymatic methods and a competition assay with mapping mAbs to characterize interaction with the target protein. RESULTS: We detected anti-factor H autoantibodies of the IgM class in seven of 186 (3.8%) patients with thrombotic microangiopathy presented as aHUS. No association was observed between anti-factor H IgM and homozygous deletions involving CFHR3-CFHR1. A significantly higher proportion of patients with bone marrow transplant-related thrombotic microangiopathy had anti-factor H IgM autoantibodies versus other patients with aHUS: three of 20 (15%) versus four of 166 (2.4%), respectively. The identified IgM autoantibodies recognize the SCR domain 19 of factor H molecule in all patients and interact with the factor H molecule, inhibiting its binding to C3b. CONCLUSIONS: Detectable autoantibodies to factor H of the IgM class may be present in patients with aHUS, and their frequency is six-fold higher in thrombotic microangiopathy forms associated with bone marrow transplant. The autoantibody interaction with factor H's active site may support an autoimmune mechanism in some cases previously considered to be of unknown origin.

Chromosome 3 cluster rs11385942 variant links complement activation with severe COVID-19.

BACKGROUND: Genetic variation at a multigene cluster at chromosome 3p21.31 and the ABO blood group have been associated with the risk of developing severe COVID-19, but the mechanism remains unclear. Complement activation has been associated with COVID-19 severity. OBJECTIVE: The aim of this study was to examine whether chromosome 3p21.31 and the ABO variants are linked to the activation of the complement cascade in COVID-19 patients. METHODS: We considered 72 unrelated European hospitalized patients with genetic data and evaluation of circulating C5a and soluble terminal complement complex C5b-9 (SC5b-9). Twenty-six (36.1%) patients carried the rs11385942 G>GA variant and 44 (66.1%) non-O blood group associated with increased risk of severe COVID-19. RESULTS: C5a and SC5-b9 plasma levels were higher in rs11385949 GA carriers than in non-carriers (P = 0.041 and P = 0.012, respectively), while C5a levels were higher in non-O group than in O group patients (P = 0.019). The association between rs11385949 and SC5b-9 remained significant after adjustment for ABO and disease severity (P = 0.004) and further correction for C5a (P = 0.018). There was a direct relationship between upper airways viral load and SC5b-9 in carriers of the rs11385949 risk allele (P = 0.032), which was not observed in non-carriers. CONCLUSIONS: The rs11385949 G>GA variant, tagging the chromosome 3 gene cluster variation and predisposing to severe COVID-19, is associated with enhanced complement activation, both with C5a and terminal complement complex, while non-O blood group with C5a levels. These findings provide a link between genetic susceptibility to more severe COVID-19 and complement activation.

Consumption of complement in a 26-year-old woman with severe thrombotic thrombocytopenia after ChAdOx1 nCov-19 vaccination.

Extremely rare reactions characterized by thrombosis and thrombocytopenia have been described in subjects that received ChAdOx1 nCoV-19 vaccination 5-16 days earlier. Although patients with vaccine-induced thrombotic thrombocytopenia (VITT) have high levels of antibodies to platelet factor 4 (PF4)-polyanion complexes, the exact mechanism of the development of thrombosis is still unknown. Here we reported serum studies as well as proteomics and genomics analyses demonstrating a massive complement activation potentially linked to the presence of anti-PF4 antibodies in a patient with severe VITT. At admission, complement activity of the classical and lectin pathways were absent (0% for both) with normal levels of the alternative pathway (73%) in association with elevated levels of the complement activation marker sC5b-9 (630 ng/mL [n.v. 139-462 ng/mL]) and anti-PF4 IgG (1.918 OD [n.v. 0.136-0.300 OD]). The immunoblotting analysis of C2 showed the complete disappearance of its normal band at 110 kDa. Intravenous immunoglobulin treatment allowed to recover complement activity of the classical pathway (91%) and lectin pathway (115%), to reduce levels of sC5b-9 (135 ng/mL) and anti-PF4 IgG (0.681 OD) and to normalize the C2 pattern at immunoblotting. Proteomics and genomics analyses in addition to serum studies showed that the absence of complement activity during VITT was not linked to alterations of the C2 gene but rather to a strong complement activation leading to C2 consumption. Our data in a single patient suggest monitoring complement parameters in other VITT patients considering also the possibility to target complement activation with specific drugs.

Complement activation and endothelial perturbation parallel COVID-19 severity and activity.

BACKGROUND: Animal models and few clinical reports suggest the involvement of the complement system in the onset of severe manifestations of coronavirus disease-2019 (COVID-19). However, complement contribution to endotheliopathy and hypercoagulability has not been elucidated yet. OBJECTIVE: To evaluate the association among complement activation, endothelial damage and disease severity or activity in COVID-19 patients. METHODS: In this single-centre cohort study, 148 patients with COVID-19 of different severity were evaluated upon hospital admission and 30 days later. Markers of complement activation (SC5b-9 and C5a) and endothelial perturbation (von Willebrand factor [vWF], tissue-type plasminogen activator [t-PA], plasminogen activator inhibitor-1 [PAI-1], soluble thrombomodulin [sTM], and soluble endothelial selectin [sE-selectin]) were measured in plasma. RESULTS: The patients had high plasma levels of SC5b-9 and C5a (p = 0.0001 for both) and vWF, t-PA and PAI-1 (p = 0.0001 for all). Their SC5b-9 levels correlated with those of vWF (r = 0.517, p = 0.0001) and paralleled disease severity (severe vs mild p = 0.0001, severe vs moderate p = 0.026 and moderate vs mild p = 0.001). The levels of sE-selectin were significantly increased only in the patients with severe disease. After 30 days, plasma SC5b-9, C5a and vWF levels had significantly decreased (p = 0.0001 for all), and 43% of the evaluated patients had normal levels. CONCLUSIONS: Complement activation is boosted during the progression of COVID-19 and dampened during remission, thus indicating its role in the pathophysiology of the disease. The association between complement activation and the biomarkers of endothelial damage suggests that complement may contribute to tissue injury and could be the target of specific therapy.

Side effects among healthcare workers from a large Milan university hospital after second dose of BNT162b2 mRNA COVID-19 vaccine.

BACKGROUND: In Italy, healthcare workers (HCWs) were among the first to receive COVID-19 vaccination. Aim of the present study is to evaluate frequency and severity of adverse events (AEs) following the second dose of BNT162b2 vaccine among HCWs of a large university hospital in Milan, Italy. METHODS: One month after having received the second dose of vaccine, HCWs filled-in a form about type, severity, and duration of post-vaccination local and systemic symptoms. We calculated the overall frequency of AEs and used multivariable Poisson regression models (adjusted for sex, age, BMI, smoking, allergy history, previous SARS-CoV-2 infection, anti-hypertensive therapy, and occupation) to calculate risk ratios (RR) and 95% confidence intervals (CI) of AEs according to selected variables. RESULTS: We included 3659 HCWs. Overall, 2801 (76.6%) experienced at least one local event, with pain at injection site being the most frequent (2788, 76.2%). Systemic events were reported by 2080 (56.8%) HCWs, with fatigue (52.3%), muscle pain (42.2%), headache (37.7%), joint pain (31.9%), and fever (26.2%) being the most frequent. Risks of systemic events were associated with female gender (RR=1.14, CI: 1.06-1.23), age (strong decrease with increasing age, p-trend<0.001), allergy history (RR=1.13, CI: 1.05-1.20), and current smoking (RR=0.90, CI: 0.84-0.97). HCWs with previous SARS-CoV-2 infection (even if symptomatic) were not at increased risk. CONCLUSIONS: Both local and systemic acute effects after second dose of BNT162b2 vaccine were frequently reported. However, symptoms were mostly light/mild and of short duration. Thus, our findings support the safety of COVID-19 vaccination in adults in relatively good health.

Hereditary Deficiency of the Second Component of Complement: Early Diagnosis and 21-Year Follow-Up of a Family.

Complement deficiencies are rare and often underdiagnosed primary immunodeficiencies that may be associated with invasive bacterial diseases. Serious infections with encapsulated organisms (mainly Streptococcus pneumoniae, but also Neisseria meningitides and Haemophilus influenzae type B) are frequent in patients with a deficiency of the second component of complement (C2), but no data are available on long-term follow-up. This study aimed to evaluate the long-term clinical outcome and the importance of an early diagnosis and subsequent infection prophylaxis in C2 deficiency. Here, we report the 21-year follow-up of a whole family which was tested for complement parameters, genetic analysis and biochemical measurements, due to recurrent pneumococcal meningitis in the elder brother. The two sons were diagnosed with homozygous type 1 C2 deficiency, while their parents were heterozygous with normal complement parameters. For the two brothers, a recommended vaccination program and antibiotic prophylaxis were prescribed. During the long-term follow-up, no severe/invasive infections were observed in either patient. At the age of 16, the younger brother developed progressive hypogammaglobulinemia of all three classes, IgA, IgM and IgG. A next generation sequencing panel excluded the presence of gene defects related to primary antibody deficiencies. Our data show that early diagnosis, use of vaccinations and antibiotic prophylaxis may allow a normal life in hereditary C2 deficiency, which can be characterized using functional and genetic methods. Moreover, a periodical check of immunoglobulin serum levels could be useful to detect a possible hypogammaglobulinemia.

Complement functional tests for monitoring eculizumab treatment in patients with atypical hemolytic uremic syndrome: an update.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy (TMA) characterized by platelet consumption, hemolysis, and organ damage. Eculizumab (ECU), a humanized antibody that blocks complement activity, has been successfully used in aHUS, but the best treatment schedule is not yet clear. METHODS: Here, we report our experience with ECU maintenance treatment and the interval between subsequent doses being extended based on global classical complement pathway (CCP) activity aimed at <30% for maintaining aHUS into remission. RESULTS: We report on 38 patients with aHUS, 13 children, 21 female, with a median age of 25.0 years (range 0.5-60) at disease onset treated with ECU standard schedule for a median of 2.6 months (range 0.4-24.6). Once stable TMA remission was obtained, the interval between ECU doses was extended based on complement function, with a target CCP activity of <30%. With this approach, 22 patients regularly receive ECU infusion every 28 days and 16 every 21. During a median observation period on ECU, an extended interval of 26.9 months (range 0.8-80.9), with a cumulative observation period of 1,208 months, none of the patients relapsed. CONCLUSION: Monitoring complement activity allows a safe reduction in the frequency of ECU administration in aHUS while keeping the disease in remission.

Acquired Complement Regulatory Gene Mutations and Hematopoietic Stem Cell Transplant-Related Thrombotic Microangiopathy.

Hematopoietic stem cell transplant-related thrombotic microangiopathy (HSCT-TMA) is a severe complication whose pathophysiology is unknown. We describe 6 patients in which the disease was associated with complement regulatory gene abnormalities received from their respective donors. It is suggested that mutated and transplanted monocyte-derived cells are responsible for production of abnormal proteins, complement dysregulation, and, ultimately, for the disease. This observation might have important drawbacks as far as HSCT-TMA pathophysiology and treatment are concerned.

Detection of early endothelial damage in patients with Raynaud's phenomenon.

OBJECTIVES: Raynaud's phenomenon (RP) can be the first manifestation of systemic sclerosis (SSc) or other connective tissue diseases (CTDs), often preceding an overt disease by years. It is not known if markers of endothelial damage are detectable in those RP patients who subsequently develop a CTD. METHODS: We studied 82 RP patients at their first evaluation to correlate the levels of endothelial markers with the subsequent development of an overt disease 36months later. We measured plasma levels of tissue-type plasminogen activator (t-PA) and von Willebrand factor (vWF), two markers of endothelial damage, and interleukin-6 (IL-6), a pro-inflammatory cytokine. Thirty sex- and age-matched healthy subjects (HS) served as controls. RESULTS: At baseline, 67 patients showed capillaroscopic normal pattern (CNP) and 15 patients, of which 11 were very early SSc, had capillaroscopic scleroderma pattern (CSP). Plasma levels of t-PA, vWF and IL-6 were higher in patients with CNP (p=0.0001) than in HS and even much higher in patients with CSP (p=0.0001). In patients with CNP and RP of recent onset (<18months), vWF plasma levels were higher when autoantibodies were present (p=0.020). After 36months, among 48 RP patients with CNP who remained in follow-up, 24 were diagnosed as primary and 24 as secondary RP. In secondary RP, basal levels of t-PA, IL-6 and particularly vWF were higher than in primary RP (p=0.005, p=0.004, p=0.0001 respectively) and HS (p=0.0001 for all). CONCLUSIONS: Our findings indicate that markers of endothelial damage are elevated in RP patients who subsequently develop SSc or other CTDs, even in the absence of capillaroscopic abnormalities.

D-Dimer Plasma Levels Parallel the Clinical Response to Omalizumab in Patients with Severe Chronic Spontaneous Urticaria.

Omalizumab is very effective in the majority of patients with severe chronic spontaneous urticaria (CSU), but its mechanism of action is still unclear. In CSU the coagulation cascade is activated with an intensity that parallels the disease severity, and elevated plasma D-dimer levels are associated with a poor response to both antihistamines and cyclosporin. We measured D-dimer plasma levels before and after the first administration of omalizumab in 32 patients with severe CSU. A number of clinical and laboratory parameters were recorded, including the urticaria activity score, presence of angioedema, disease duration, C-reactive protein, anti-nuclear, and anti-thyroid antibodies. Baseline D-dimer levels were elevated in 19 (59%) cases. Omalizumab induced a complete response in 25 patients (78%), in most cases already after the first administration. At baseline, 14/25 responders had increased D-dimer plasma levels versus 5/7 non-responders. All responders showed a dramatic decrease of D-dimer plasma levels after the first administration of the drug (from 1,024 ± 248 [mean ± SE] to 251 ± 30 ng/mL; p = 0.003). In contrast, non-responders did not show any reduction in D-dimer levels after omalizumab administration (from 787 ± 206 to 1,230 ± 429 ng/mL; p = ns). In conclusion, plasma levels of D-dimer are frequently elevated in patients with severe CSU before omalizumab administration and decrease according to the clinical response of the disease to the drug, suggesting a possible effect of omalizumab on coagulation activation and fibrin degradation in a subset of CSU patients.

Prothrombotic biomarkers in patients with rheumatoid arthritis: the beneficial effect of IL-6 receptor blockade.

OBJECTIVES: The pro-inflammatory cytokine interleukin (IL)-6 is involved in the pathogenesis of both rheumatoid arthritis (RA) and cardiovascular events. We evaluated the correlation of prothrombotic biomarkers, in particular those of thrombin generation, with inflammatory and clinical parameters in RA patients treated with tocilizumab, an IL-6 receptor (IL-6R) inhibitor. Naïve and maintenance patients were compared. METHODS: We studied 15 RA patients undergoing tocilizumab infusions at a University Outpatient Clinic. Eight received tocilizumab for the first time and were evaluated at baseline. Seven were in maintenance therapy (9 to 77 months). All 15 patients were evaluated four weeks after the last administration of tocilizumab. At each time, we assessed disease activity score 28 (DAS28), erythrocyte sedimentation rate (ESR) and plasma levels of C-reactive protein (CRP), IL-6, soluble (s)IL-6R, tumour necrosis factor-alpha (TNF-alpha), prothrombin fragment F1+2 and fibrin fragment D-dimer. Forty healthy subjects served as basal controls. RESULTS: At baseline, RA patients showed a moderate-to-high disease activity and median ESR of 51 mm/1(st) hour (interquartile range 25-63). Plasma levels of CRP (p=0.0001), IL-6 (p=0.043), sIL-6R (p=0.003), TNF-alpha (p=0.0001), F1+2 (p=0.0001) and D-dimer (p=0.002) were higher than those of healthy controls. After four weeks we observed reduction of DAS28 (p=0.0001), ESR (p=0.0001), CRP (p=0.014), TNF-alpha (p=0.006), F1+2 (p=0.009) and D-dimer (p=0.04). No differences were observed between naïve and maintenance patients. CONCLUSIONS: The reduction of prothrombotic biomarkers parallels the reduction of inflammatory parameters and clinical symptoms in RA patients treated with tocilizumab, both four weeks after the first administration and during maintenance therapy.

Discontinuation of eculizumab maintenance treatment for atypical hemolytic uremic syndrome: a report of 10 cases.

Atypical hemolytic uremic syndrome (aHUS) is a life-threatening thrombotic microangiopathy, and as many as 70% of patients with aHUS have mutations in the genes encoding complement regulatory proteins. Eculizumab, a humanized recombinant monoclonal antibody targeting C5, has been used successfully in patients with aHUS since 2009. The standard maintenance treatment requires life-long eculizumab therapy, but the possibility of discontinuation has not yet been tested systematically. We report the safety of discontinuing eculizumab treatment in 10 patients who stopped treatment with the aim of minimizing the risk of adverse reactions, reducing the risk of meningitis, and improving quality of life while also reducing the considerable treatment costs. Disease activity was monitored closely at home by means of urine dipstick testing for hemoglobin. During the cumulative observation period of 95 months, 3 of the 10 patients experienced relapse within 6 weeks of discontinuation, but then immediately resumed treatment and completely recovered. Our experience supports the possibility of discontinuing eculizumab therapy with strict home monitoring for early signs of relapse in patients with aHUS who achieve stable remission.

Outcome of atypical hemolytic uremic syndrome: role of triggers and complement abnormalities in the response to C5 inhibition.

BACKGROUND: Atypical-hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy often due to uncontrolled complement activation, characterized by high risk of end-stage kidney disease (ESKD). Eculizumab has improved the outcome, however, its efficacy varies among patients and its discontinuation is debated. METHODS: To identify characteristics associated with treatment response, we analyzed 244 aHUS patients referred to our center. Patients were classified according to the presence/absence of complement abnormalities and/or triggers at onset in 4 categories: (1) primary (complement abnormality without trigger), (2) secondary (trigger without complement abnormality), (3) combined (trigger and complement abnormality), (4) idiopathic (no trigger, no complement abnormality). Response to treatment was evaluated by comparing the response to eculizumab with that of conventional therapy. Short- and long-term outcomes were evaluated with the relapse rate after discontinuation of C5-inhibition. RESULTS: Patients had a better outcome with eculizumab compared to conventional treatment, with a response rate of 81.9% vs 56.9%, p < 0.001 and a long-term cumulative incidence of ESKD of 5.8% vs 22.5% (hazard ratio 0.25, 95% confidence interval: 0.10-0.80). The excellent global response was driven by the primary and combined groups (89.8% vs 54.0% and 89.3% vs 54.2%, respectively). The relapse rate following discontinuation of the C5-inhibitor was as high as 66.7% in the primary group, 18.7% in the combined, and 0% in the secondary and idiopathic groups. CONCLUSIONS: Our data show a better outcome in aHUS patients treated with C5-inhibition, particularly in the primary and combined forms, which have a high risk of relapse after discontinuation that is not observed in the secondary and idiopathic forms.