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Cutaneous vasculitis is an inflammatory disease affecting the dermal blood vessel walls. The skin is a privileged organ in the setting of vasculitis since it is easily accessible for physical examination and safe biopsy, allowing an accurate characterization of inflammatory lesions. The skin is often involved. Also, cutaneous vasculitis can reflect a cutaneous component of a systemic vasculitis, a skin-limited or skin-dominant expression or variant of a systemic vasculitis, or be a single-organ vasculitis per se. Vasculitis lesions are multiple and polymorphic. They may induce a wide spectrum of clinical manifestations depending on the location and the size of the vessels involved. The depth of affected vessels is correlated with the type of cutaneous lesions. Involvement of small superficial vessels results mostly in urticarial, but relatively persistent plaques, papules, and palpable purpura. Involvement of vessels in the dermohypodermic junction or hypodermis results in ulcers, nodules, or livedo. The type of inflammatory infiltrate is also a key finding for the diagnosis of cutaneous vasculitis. Leukocytoclastic vasculitis is not a disease per se but the result of a pathophysiological process common to different causes. A better knowledge of the vascular anatomy of the skin, elementary lesions, and histological characteristics of dermatologic manifestations would allow a more relevant and more efficient diagnostic approach. We also propose a list of additional exams to be performed in front of skin lesions suggestive of vasculitis. The aim of our article is to provide an overview of elementary skin lesions and clinicopathologic correlations in cutaneous and systemic vasculitis.

Objective To contrast the effect of the burden of vasculitis activity with the burden of adverse events on 1-year mortality of patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Methods This study assessed the outcome and adverse events in patients prospectively recruited to four European AAV clinical trials. Data on 524 patients with newly diagnosed AAV were included. The burden of adverse events was quantified using a severity score for leucopenia, infection and other adverse events, with an additional weighting for follow-up duration. A ‘combined burden of events’ (CBOE) score was generated for each patient by summing the individual scores. Vasculitis severity was quantified using the Birmingham vasculitis activity score and glomerular filtration rate (GFR). Results 1-year mortality probability was 11.1%; 59% and 14% of deaths were caused by therapy-associated adverse events and active vasculitis, respectively. Using Cox regression analysis, infection score (p<0.001), adverse event score (p<0.001), leucopenia score (p<0.001) and GFR (p=0.002) were independently associated with mortality. The risk of 1-year mortality remained low (5%) with CBOE scores less than 7, but increased dramatically with scores above this. Hazard ratio for death with a CBOE greater than 7 was 14.4 (95% CI 8.4 to 24.8). Age and GFR were independent predictors of CBOE score. Conclusions The greatest threat to patients with AAV in the first year of therapy is from adverse events rather than active vasculitis. The accumulation of adverse events, monitored using this scoring method, should prompt increased awareness that the patient is at high risk of death.

The systemic vasculitides are a group of uncommon diseases characterized by blood vessel inflammation. There are currently no diagnostic criteria for the primary systemic vasculitides and physicians must rely on experience and disease definitions. The absence of validated criteria can result in delays in making the correct diagnosis and starting appropriate therapy. With the increased understanding of the pathophysiology of vasculitis and newer diagnostic tests in widespread clinical use, it is an appropriate time for classification criteria for primary vasculitis to be revised. The Diagnostic and Classification Criteria for Vasculitis (DCVAS) study is a multinational observational study designed to develop and validate diagnostic criteria and to improve and validate classification criteria for primary systemic vasculitis. The analytic approach will be based on the traditional approach of vessel size for classification of vasculitis but will also incorporate detailed clinical data, evaluation of anti-neutrophil cytoplasm antibody diagnostic testing, biopsy and imaging data. The study is following the guidelines for the development of classification criteria established by the American College of Rheumatology and the European League against Rheumatism. The study will incorporate the use of pre-defined cases of each condition to reduce the inherent circularity when developing new classification criteria and will explore alternative approaches to deriving reference standards by creating data-driven classification algorithms. We anticipate recruiting >2,000 patients with primary systemic vasculitis and 1,500 patients with autoimmune diseases and other conditions that mimic vasculitis. As of June 2013, >100 medical centers across 31 countries in Asia, Australasia, Europe, North America, and South America were contributing data to the study. The DCVAS study provides a unique opportunity to increase generalizability and collate a large dataset on the occurrence, presentation, and outcome of vasculitis in different populations.

Key Points The complement system provides essential protection against infections but also contributes to the severity of autoimmune diseases The complement system is activated in many rheumatic diseases, as evident from deposition of activation fragments in affected tissue, decreased residual complement function and increased levels of circulating activated complement fragments Although complement is activated in rheumatic diseases, this finding does not mean that complement has a major role in the clinical presentation Systemic complement inhibition is feasible and reasonably safe when the right precautions are taken Complement inhibition has not yet become a common therapeutic strategy for rheumatic disease In this review, the authors evaluate the association of complement activation with a variety of rheumatic diseases, including rheumatoid arthritis, systemic lupus erythematosus and small-vessel vascultis, and discuss whether complement inhibition has therapeutic potential in these diseases. Complement activation is associated with common rheumatic diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and systemic vasculitis. Evidence linking complement activation to these diseases includes the presence of complement deposition in affected tissues, decreased levels of complement proteins and high levels of complement activation fragments in the blood and/or synovial fluid of patients with these diseases, as well as data from experimental models. Eculizumab, a monoclonal antibody that inhibits the complement component C5, is now approved for the treatment of rare conditions involving complement hyperactivation, and the success of this therapy has renewed interest in understanding the utility of complement inhibition in rheumatological practice, particularly for SLE. For example, inhibiting C5 is a potential means of reducing glomerular inflammation in lupus nephritis or treating thrombotic microangiopathy in SLE. The complement system is one of multiple mediators of tissue injury in complex diseases such as SLE, and identifying the disease context in which complement activation has a predominant role is a challenge. An added difficulty in RA is identifying a role for therapeutic complement inhibition within the diverse treatment modalities already available. In this Review, evidence for the therapeutic potential of complement manipulation in rheumatology practice is evaluated.

Giant cell arteritis (GCA) is a common form of primary systemic vasculitis in adults, with no reliable indicators of prognosis or treatment responses. We used single cell technologies to comprehensively map immune cell populations in the blood of patients with GCA and identified the CD66b + CD15 + CD10 lo/– CD64 – band neutrophils and CD66b hi CD15 + CD10 lo/– CD64 +/bright myelocytes/metamyelocytes to be unequivocally associated with both the clinical phenotype and response to treatment. Immature neutrophils were resistant to apoptosis, remained in the vasculature for a prolonged period of time, interacted with platelets, and extravasated into the tissue surrounding the temporal arteries of patients with GCA. We discovered that immature neutrophils generated high levels of extracellular reactive oxygen species, leading to enhanced protein oxidation and permeability of endothelial barrier in an in vitro coculture system. The same populations were also detected in other systemic vasculitides. These findings link functions of immature neutrophils to disease pathogenesis, establishing a clinical cellular signature of GCA and suggesting different therapeutic approaches in systemic vascular inflammation.

Vasculitides are a heterogeneous group of disorders characterized by inflammation of blood vessel walls, leading to tissue ischemia and organ injury. Traditional inflammatory markers such as the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are widely used but lack diagnostic specificity. This has driven the search for more informative biomarkers across vasculitis subtypes. This review summarizes current evidence for validated and emerging biomarkers in large-, medium-, small-, and variable-vessel vasculitis, as well as single-organ vasculitis. Key analytes reflect systemic inflammation, such as serum amyloid A (SAA) and interleukin-6 (IL-6), as well as endothelial activation, complement pathways, neutrophil and macrophage activation, and organ-specific damage. Promising candidates include pentraxin-3 (PTX3) and matrix metalloproteinase-9 (MMP-9) in large-vessel vasculitis; N-terminal pro-B-type natriuretic peptide (NT-proBNP) and S100 proteins in Kawasaki disease; galactose-deficient immunoglobulin A1 (Gd-IgA1) and urinary angiotensinogen (AGT) in IgA vasculitis; and tissue inhibitor of metalloproteinases-1 (TIMP-1), S100 proteins, complement C3, and PTX3 in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Although these biomarkers provide mechanistic insight, most lack disease-specificity, external validation, or standardized assays. Future progress will require multicenter studies, harmonized testing, and integrated biomarker panels combined with imaging modalities to improve diagnosis, activity assessment, and monitoring.

Purpose The role of fibroblast activation protein (FAP)-targeted imaging in systemic vasculitis is currently unclear. We aimed to evaluate the clinical value of fluorine-18-labeled FAP inhibitor 42 ([ 18 F]FAPI-42) in patients with systemic vasculitis and to compare with [ 18 F]fluorodeoxyglucose (FDG) imaging. Methods Patients with systemic vasculitis who underwent dual-tracer PET/CT([ 18 F]FDG and [ 18 F]FAPI) imaging from September 2020 to March 2022 were retrospectively analyzed. Positive lesions are defined as vascular/extravascular lesions with increased tracer uptake above surrounding background, which cannot be attributed to the physiologic biodistribution of the radiotracer. The vascular/extravascular lesion detection rate and semiquantitative values (SUVmax, TBR blood and TBR liver ) of [ 18 F]FAPI and [ 18 F]FDG were compared, and the correlation between the extent and range of tracer uptake and levels of inflammatory markers was investigated. Results Thirty patients (13 males and 17 females; mean age, 52.5 ± 17.2 years) with systemic vasculitis were included (17 large vessel vasculitis, 10 anti-neutrophil cytoplasmic antibody-associated vasculitis, 2 Behcet’s disease and 1 polyarteritis nodosa). [ 18 F]FDG PET/CT had positive findings in 93.3% (28/30) of patients, while [ 18 F]FAPI PET/CT had positive findings in all patients (100%, P  = 0.500). Compared with [ 18 F]FDG PET/CT, [ 18 F]FAPI PET/CT detected more lesions (161/168 vs. 145/168, P  = 0.005), and more extensive vascular involvement in 60% (18/30) of patients. Although SUVmax did not differ significantly between [ 18 F]FAPI and [ 18 F]FDG (median, 5.94 vs. 5.46, P  = 0.517), [ 18 F]FAPI had higher TBR liver (median, 9.59 vs. 3.15, P  < 0.001) and TBR blood (median, 5.45 vs. 4.20, P  = 0.006). The total number of positive lesions in FAPI PET/CT show a moderate correlation with erythrocyte sedimentation rate ( r s =0.478, P  = 0.008) and C-reactive protein ( r s =0.486, P  = 0.006). After treatment, follow-up FAPI PET/CT of 6 patients showed decreased SUVmax, TBR and number of detected lesions, paralleling the clinical remission. Conclusion [ 18 F]FAPI PET/CT imaging is a promising imaging modality for the diagnosis and therapeutic monitoring of systemic vasculitis.

IgA vasculitis (IgAV) is a small-vessel vasculitis characterized by immune complex deposition, neutrophil activation, and endothelial injury. S100 proteins are recognized mediators of inflammation and vascular damage; however, their specific biological and clinical relevance in IgAV remains incompletely understood. This systematic review aimed to synthesize current evidence on the mechanistic and clinical roles of S100 proteins in vasculitides, focusing on IgAV, and to evaluate their potential utility as biomarkers of disease activity, organ involvement, and prognosis. A PRISMA-compliant systematic search was conducted in PubMed, Embase, Scopus, and Web of Science up to November 18, 2025. Original human studies investigating S100A8/9, S100A12, S100A4, and S100A10 in any form of vasculitis or related vascular inflammation were included. Data were synthesized narratively following an independent risk-of-bias assessment. Fifty-four studies met the inclusion criteria. Available evidence supports the role of S100A8/9 and S100A12 as markers of neutrophil-driven inflammation and disease activity in systemic vasculitides, with emerging evidence suggesting relevance in IgAV. In contrast, findings on S100A4 and S100A10 were fragmentary and indirect, indicating a mechanistic contribution but lacking sufficient IgAV-specific data. S100 proteins may act as mediators in the IgAV inflammatory cascade. However, the current evidence base remains fragmented. Although S100A8/9 appears promising, standardized prospective studies are required for S100A12, S100A4, and S100A10 to establish their clinical validity for risk stratification.

Different vasculitic syndromes present in different age groups. Immunoglobulin (Ig)A vasculitis and Kawasaki disease usually present in children whereas giant cell arteritis (GCA) and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis usually present in the middle aged/elderly. In Northern Europe, granulomatosis with polyangiitis (GPA; Wegener’s) is commoner than microscopic polyangiitis (MPA) and MPA is more common than eosinophilic granulomatosis with polyangiitis (EPGA; Churg−Strauss syndrome). In Southern Europe, MPA is commoner than GPA and in Japan MPA is much more common than GPA. Major differences exist worldwide in ANCA specificity which are not entirely related to different phenotypes. GPA, like GCA, has a cyclical pattern of onset suggesting possible infection as an aetiological agent. International studies have given important clues to possible aetiology including silica dust and infection and genetic influences, as shown by the recently published genome-wide association study which revealed that single-nucleotide polymorphisms associate more strongly with ANCA than clinical syndromes. A brief description of the main clinical features of ANCA-associated vasculitis is also given.

Little is known about the epidemiology of systemic vasculitis in South American countries. The aim of this study is to compare the prevalence of systemic vasculitides in two vasculitis referral centers from Brazil and Peru. A cross-sectional study was performed and all patients above 18 years of age, with at least 6 months of follow-up and who met classification or diagnosis criteria for the most common forms of vasculitis, were included. A total of 562 patients with systemic vasculitis were analyzed, 345 (61.4%) from Brazil and 217 (38.6%) from Peru. The frequency of Behçet’s disease (37.9% vs. 1.8%; p  < 0.0001), Takayasu arteritis (TAK) (25.2% vs. 6.9%; p  < 0.0001), and giant cell arteritis (9.8% vs. 0.9%; p  < 0.0001) was higher in the Brazilian center than the Peruvian one. On the other hand, the frequency of microscopic polyangiitis (MPA) (67.3% vs. 2.8%; p  < 0.0001) and renal-limited vasculitis (2.8% vs. 0.0%; p  = 0.009) was higher in the Peruvian center. No differences were found concerning other forms of vasculitis. At diagnosis, Brazilian patients with TAK, granulomatosis with polyangiitis, and MPA were younger than Peruvian patients. Epidemiologic differences in the frequency of systemic vasculitis are observed between a vasculitis referral center from Brazil and another from Peru. Key Points • Significant differences are observed regarding the epidemiologic profile of systemic vasculitis between Brazil and Peru. • MPA is the predominant form of vasculitis in Peru while BD and TAK are the most frequent forms of vasculitis in Brazil. • The age at diagnosis of TAK, MPA, and GPA was lower in Brazilian patients than in Peruvian patients.