Identification of new risk loci shared across systemic vasculitides points towards potential target genes for drug repurposing.

OBJECTIVES: The number of susceptibility loci currently associated with vasculitis is lower than in other immune-mediated diseases due in part to small cohort sizes, a consequence of the low prevalence of vasculitides. This study aimed to identify new genetic risk loci for the main systemic vasculitides through a comprehensive analysis of their genetic overlap. METHODS: Genome-wide data from 8467 patients with any of the main forms of vasculitis and 29 795 healthy controls were meta-analysed using ASSET. Pleiotropic variants were functionally annotated and linked to their target genes. Prioritised genes were queried in DrugBank to identify potentially repositionable drugs for the treatment of vasculitis. RESULTS: Sixteen variants were independently associated with two or more vasculitides, 15 of them representing new shared risk loci. Two of these pleiotropic signals, located close to CTLA4 and CPLX1, emerged as novel genetic risk loci in vasculitis. Most of these polymorphisms appeared to affect vasculitis by regulating gene expression. In this regard, for some of these common signals, potential causal genes were prioritised based on functional annotation, including CTLA4, RNF145, IL12B, IL5, IRF1, IFNGR1, PTK2B, TRIM35, EGR2 and ETS2, each of which has key roles in inflammation. In addition, drug repositioning analysis showed that several drugs, including abatacept and ustekinumab, could be potentially repurposed in the management of the analysed vasculitides. CONCLUSIONS: We identified new shared risk loci with functional impact in vasculitis and pinpointed potential causal genes, some of which could represent promising targets for the treatment of vasculitis.

Cambio de paradigma en las enfermedades autoinflamatorias monogénicas y las vasculitis sistémicas: el síndrome VEXAS / Paradigm shift in monogenic autoinflammatory diseases and systemic vasculitis: The VEXAS syndrome

A finales de 2020 se describió el síndrome VEXAS, como una enfermedad autoinflamatoria causada por variantes poscigóticas en el gen UBA1. Se presenta en varones adultos con fiebre recurrente, artralgias/artritis, condritis auricular/nasal, dermatosis neutrofílica, inflamación pulmonar, trombosis venosas y diferentes tipos de vasculitis. Los análisis muestran una respuesta de fase aguda elevada y anemia macrocítica. Es frecuente la coexistencia de mielodisplasia, y son características las vacuolas citoplasmáticas en precursores mieloides y eritroides en médula ósea. Los glucocorticoides a dosis medias-altas son eficaces, pero el resto de fármacos inmunodepresores, convencionales o biológicos, muestran una eficacia limitada o ausente. Azacitidina se ha asociado con una buena respuesta, sobre todo en pacientes con síndrome mielodisplásico acompañante. El trasplante alogénico de progenitores hematopoyéticos parece ser la única terapia curativa hasta el momento. El síndrome VEXAS ha supuesto un cambio de paradigma en el diagnóstico y tratamiento de las enfermedades autoinflamatorias y las vasculitis sistémicas. (AU)

VEXAS syndrome was described by the end of 2020 as an autoinflammatory disease caused by post-zygotic variants in the UBA1 gene. VEXAS syndrome occurs in adult males with recurrent fever, arthralgia/arthritis, ear/nose chondritis, neutrophilic dermatosis, lung inflammation, venous thrombosis, and different types of vasculitis. Common laboratory changes include raised acute phase reactants and macrocytic anemia. The coexistence of myelodysplasia is frequent, and bone marrow vacuolization of myeloid and erythroid precursors is characteristic. Glucocorticoids are effective at medium-high doses, but the remaining immunosuppressive drugs, either conventional or biological, have showed limited or absent efficacy. Azacitidine has been associated with a good response, especially in patients with accompanying myelodysplastic syndrome. Allogeneic hematopoietic stem cell transplantation appears to be the only curative therapy by now. VEXAS syndrome has become a paradigm shift in the diagnosis and treatment of autoinflammatory diseases and systemic vasculitis. (AU)

Paradigm shift in monogenic autoinflammatory diseases and systemic vasculitis: The VEXAS syndrome. / Cambio de paradigma en las enfermedades autoinflamatorias monogénicas y las vasculitis sistémicas: el síndrome VEXAS.

VEXAS syndrome was described by the end of 2020 as an autoinflammatory disease caused by post-zygotic variants in the UBA1 gene. VEXAS syndrome occurs in adult males with recurrent fever, arthralgia/arthritis, ear/nose chondritis, neutrophilic dermatosis, lung inflammation, venous thrombosis, and different types of vasculitis. Common laboratory changes include raised acute phase reactants and macrocytic anemia. The coexistence of myelodysplasia is frequent, and bone marrow vacuolization of myeloid and erythroid precursors is characteristic. Glucocorticoids are effective at medium-high doses, but the remaining immunosuppressive drugs, either conventional or biological, have showed limited or absent efficacy. Azacitidine has been associated with a good response, especially in patients with accompanying myelodysplastic syndrome. Allogeneic hematopoietic stem cell transplantation appears to be the only curative therapy by now. VEXAS syndrome has become a paradigm shift in the diagnosis and treatment of autoinflammatory diseases and systemic vasculitis.

Usefulness of vasculitis biomarkers in the era of the personalized medicine.

In recent years, insight into immune pathogenesis and treatment of primary systemic vasculitides (PSV) has increased considerably, and has led to the development of many clinically relevant biomarkers. This review aims to provide an update on the main biomarkers discovered and their potential application to precision medicine in vasculitis. Genetic and molecular profiling of patients and promising biomarkers discoveries are very important for personalized medicine; however, there are very limited data in PSV. Genetic studies including mainly genome-wide association studies (GWAS) had led to important discoveries in disease pathogenesis of PSV while whole exome sequencing studies lead to discovery of monogenic vasculitides. Although there are numerous studies addressing novel biomarkers in PSV, few of these biomarkers are currently being used in routine clinical practice in the management of patients with PSV. Current studies indicate that ANCA types identify distinct prognostic subsets of ANCA vasculitis patients. Today, biomarkers-driven treatment algorithms are not available in PSV.

Identification of Novel Adenosine Deaminase 2 Gene Variants and Varied Clinical Phenotype in Pediatric Vasculitis.

OBJECTIVE: Individuals with deficiency of adenosine deaminase 2 (DADA2), a recently recognized autosomal recessive disease, present with various systemic vascular and inflammatory manifestations, often with young age at disease onset or with early onset of recurrent strokes. Their clinical features and histologic findings overlap with those of childhood-onset polyarteritis nodosa (PAN), a primary "idiopathic" systemic vasculitis. Despite similar clinical presentation, individuals with DADA2 may respond better to biologic therapy than to traditional immunosuppression. The aim of this study was to screen an international registry of children with systemic primary vasculitis for variants in ADA2. METHODS: The coding exons of ADA2 were sequenced in 60 children and adolescents with a diagnosis of PAN, cutaneous PAN, or unclassifiable vasculitis (UCV), any chronic vasculitis with onset at age 5 years or younger, or history of stroke. The functional consequences of the identified variants were assessed by ADA2 enzyme assay and immunoblotting. RESULTS: Nine children with DADA2 (5 with PAN, 3 with UCV, and 1 with antineutrophil cytoplasmic antibody-associated vasculitis) were identified. Among them, 1 patient had no rare variants in the coding region of ADA2 and 8 had biallelic, rare variants (minor allele frequency <0.01) with a known association with DADA2 (p.Gly47Arg and p.Gly47Ala) or a novel association (p.Arg9Trp, p.Leu351Gln, and p.Ala357Thr). The clinical phenotype varied widely. CONCLUSION: These findings support previous observations indicating that DADA2 has extensive genotypic and phenotypic variability. Thus, screening ADA2 among children with vasculitic rash, UCV, PAN, or unexplained, early-onset central nervous system disease with systemic inflammation may enable an earlier diagnosis of DADA2.

Evolving concepts in classification of systemic vasculitis: where are we and what is the way forward?

The classification of the systemic vasculitides has been controversial for several decades. The Chapel Hill consensus Conference definitions originally developed in 1994, but revised and extended in 2012 are now widely accepted. The American College of Rheumatology (ACR) criteria were first published in 1990, are now generally accepted to be out of date and new criteria are needed. More recently the classical division of the ANCA vasculitides using clinical phenotype has come under scrutiny with evidence from epidemiological, genetic and outcome studies that perhaps these conditions should be classified on the basis of ANCA specificity into PR3-ANCA positive and MPO-ANCA positive groups. The traditional distinction between giant cell arteritis and Takayasu arteritis has been questioned and some recent studies of GCA have included patients with only extra-cranial disease. The Diagnostic and Classification Criteria of Vasculitis study (DCVAS) will provide new validated classification criteria for the systemic vasculitides.

Cross-phenotype analysis of Immunochip data identifies KDM4C as a relevant locus for the development of systemic vasculitis.

OBJETIVE: Systemic vasculitides represent a heterogeneous group of rare complex diseases of the blood vessels with a poorly understood aetiology. To investigate the shared genetic component underlying their predisposition, we performed the first cross-phenotype meta-analysis of genetic data from different clinically distinct patterns of vasculitis. METHODS: Immunochip genotyping data from 2465 patients diagnosed with giant cell arteritis, Takayasu's arteritis, antineutrophil cytoplasmic antibody-associated vasculitis or IgA vasculitis as well as 4632 unaffected controls were analysed to identify common susceptibility loci for vasculitis development. The possible functional consequences of the associated variants were interrogated using publicly available annotation data. RESULTS: The strongest association signal corresponded with an intergenic polymorphism located between HLA-DQB1 and HLA-DQA2 (rs6932517, P=4.16E-14, OR=0.74). This single nucleotide polymorphism is in moderate linkage disequilibrium with the disease-specific human leucocyte antigen (HLA) class II associations of each type of vasculitis and could mark them. Outside the HLA region, we identified the KDM4C gene as a common risk locus for vasculitides (highest peak rs16925200, P=6.23E-07, OR=1.75). This gene encodes a histone demethylase involved in the epigenetic control of gene expression. CONCLUSIONS: Through a combined analysis of Immunochip data, we have identified KDM4C as a new risk gene shared between systemic vasculitides, consistent with the increasing evidences of the crucial role that the epigenetic mechanisms have in the development of complex immune-mediated conditions.

Vasculitis update: pathogenesis and biomarkers.

Better understanding of the pathogenesis and treatment of primary systemic vasculitides (PSV) has led to the development of many potentially clinically relevant biomarkers. Genome-wide association studies have highlighted that MHC class II polymorphisms may influence the development of particular anti-neutrophil cytoplasmic antibody (ANCA) serotypes, but not the clinical phenotype of ANCA-associated vasculitis (AAV). Although ANCAs are overall poor biomarkers of disease activity, they may be useful for the prediction of flares of renal and/or pulmonary vasculitis. Moreover, patients with proteinase 3 (PR3)-AAV may respond better to rituximab than cyclophosphamide. Newer biomarkers of renal vasculitis in AAV include urinary soluble CD163, and may in the future reduce the requirement for renal biopsy. Better understanding of dysregulated neutrophil activation in AAV has led to the identification of novel biomarkers including circulating microparticles, and neutrophil extracellular traps (NETs), although their clinical utility has not yet been realised. Studies examining endothelial injury and repair responses have additionally revealed indices that may have utility as disease activity and/or prognostic biomarkers. Last, next-generation sequencing technologies are revealing monogenic forms of vasculitis, such as deficiency of adenosine deaminase type 2 (DADA2), and are profoundly influencing the approach to the diagnosis and treatment of vasculitis in the young.

An update on the role of epigenetics in systemic vasculitis.

PURPOSE OF REVIEW: The purpose of this review is to discuss recent observations of epigenetic changes related to the complex pathogenesis of systemic vasculitides and their contribution to the field. RECENT FINDINGS: There have been new observations of epigenetic changes in vasculitis and their potential role in disease pathogenesis in antineutrophil cytoplasmic antibody-associated vasculitis, giant-cell arteritis, Kawasaki disease, Behçet's disease, and IgA vasculitis. Some of this recent work has focused on the efficacy of using DNA methylation and miRNA expression as clinical biomarkers for disease activity and how DNA methylation and histone modifications interact to regulate disease-related gene expression. SUMMARY: DNA methylation, histone modification, and miRNA expression changes are all fruitful ground for biomarker discovery and therapeutic targets in vasculitis. Current knowledge has provided targeted and suggested effects, but in many cases, has relied upon small cohorts, cosmopolitan cell populations, and limited knowledge of functional interactions. Expanding our knowledge of how these epigenetic mechanisms interact in a disease-specific and cell-specific manner will help to better understand the pathogenesis of systemic vasculitis.

Alpha-1 antitrypsin Pi*SZ genotype: estimated prevalence and number of SZ subjects worldwide.

The alpha-1 antitrypsin (AAT) haplotype Pi*S, when inherited along with the Pi*Z haplotype to form a Pi*SZ genotype, can be associated with pulmonary emphysema in regular smokers, and less frequently with liver disease, panniculitis, and systemic vasculitis in a small percentage of people, but this connection is less well established. Since the detection of cases can allow the application of preventive measures in patients and relatives with this congenital disorder, the objective of this study was to update the prevalence of the SZ genotype to achieve accurate estimates of the number of Pi*SZ subjects worldwide, based on studies performed according to the following criteria: 1) samples representative of the general population, 2) AAT phenotyping characterized by adequate methods, and 3) selection of studies with reliable results assessed with a coefficient of variation calculated from the sample size and 95% confidence intervals. Studies fulfilling these criteria were used to develop tables and maps with an inverse distance-weighted (IDW) interpolation method, to provide numerical and geographical information of the Pi*SZ distribution worldwide. A total of 262 cohorts from 71 countries were included in the analysis. With the data provided by these cohorts, a total of 1,490,816 Pi*SZ were estimated: 708,792 in Europe; 582,984 in America and Caribbean; 85,925 in Africa; 77,940 in Asia; and 35,176 in Australia and New Zealand. Remarkably, the IDW interpolation maps predicted the Pi*SZ prevalence throughout the entire world even in areas lacking real data. These results may be useful to plan strategies for future research, diagnosis, and management of affected individuals.

[Cryoglobulinemic vasculitis in chronic hepatitis C: Genetic aspects]. / Geneticheskie aspekty krioglobulinemicheskogo vaskulita pri khronicheskom gepatite S.

Cryoglobulinemia (CG) is detected in more than 50% of patients with chronic hepatitis C (CHC); however, only 15-25% of them develop cryoglobulinemic vasculitis (CV) that is a systemic vasculitis due to the formation of immune deposits, which affects small (less than medium-sized) vessels and which is frequently fatal for the patient. The causes of CG only in some patients with CHC and the pathogenesis of CV remain unstudied; however, the accumulated data allow one to identify the special contribution of the patient's genetic factors to the development of the disease. The paper considers the genetic aspects of the development of CG and CV in CHC.

Identification of potential gene targets in systemic vasculitis using DNA microarray analysis.

The present study aimed to identify the involvement of critical genes in systemic vasculitis, to gain an improved understanding of the molecular circuity and to investigate novel potential gene targets for systemic vasculitis treatment. The dual­color cDNA microarray data of GSE16945, consisting of peripheral mononuclear blood cell specimens from 13 patients with systemic vasculitis and 16 healthy controls, was downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were screened in systemic vasculitis compared with controls using BRB ArrayTools, followed by the construction of a protein­protein interaction (PPI) network using the clusterProfiler package, and significant functional interaction (FI) module selection. Furthermore, transcriptional factors (TFs) among the identified DEGs were predicted and a transcriptional regulation network was constructed. A total of 173 up- and 93 downregulated genes were identified, which were mainly associated with immune response pathways. FBJ murine osteosarcoma viral oncogene homolog (FOS), ubiquitin B (UBB), signal transducer and activator of transcription 1 (STAT1) and MX dynamin­like GTPase 1 (MX1) were identified as hub proteins in the PPI network. Furthermore, UBB, FOS, and STAT1 were hub proteins in the three identified FI modules, respectively. In total, nine TFs were predicted among the DEGs. Of the DEGs that were predicted to be TFs, STAT1, v­maf avian musculoaponeurotic fibrosarcoma oncogene homolog B (MAFB) and tyrosine 3­monooxygenase/tryptophan 5­monooxygenase activation protein Z (YWHAZ), which interacted with each other, were identified to regulate further DEGs as target genes. Various genes, including FOS, UBB, MX1, STAT1, MAFB, and YWHAZ may be potential targets useful for the treatment of systemic vasculitis.

Epigenomic functional characterization of genetic susceptibility variants in systemic vasculitis.

Systemic vasculitides are poorly understood inflammatory diseases of the blood vessels that are frequently associated with significant organ damage. Genetic risk variants contribute to the susceptibility of vasculitis, but functional consequences of these genetic variants are largely unknown. Most genetic risk variants in immune-mediated diseases, including systemic vasculitis, are localized to non-coding genetic regions suggesting they might increase disease risk by influencing regulatory elements within the genome. Long range regulatory interactions pose an additional obstacle in localizing functional consequences associated with risk variants to specific genes or cell types. We used cell-type specific enrichment patterns of histone changes that mark poised, primed, and active enhancers, and DNase hypersensitivity to identify specific immune cells mediating genetic risk in vasculitis. Our data suggest that genetic risk variants in ANCA-associated vasculitis are significantly enriched in enhancer elements in Th17 cells, supporting a role for Th17 cells in this disease. Primed and active enhancer elements in B cells can be potentially affected by genetic risk variants associated with Kawasaki disease. Genetic risk in Behçet's disease and Takayasu arteritis might affect enhancer elements in multiple cell types, possibly explained by influencing enhancers in hematopoietic stem cells. Interestingly, our analyses indicate a role for B cells in Kawasaki disease, Behçet's disease, and Takayasu arteritis, and suggest that further work to characterize the involvement of B cells in these diseases is warranted.

The Contribution of Transcriptomics to Biomarker Development in Systemic Vasculitis and SLE.

A small but increasing number of gene expression based biomarkers are becoming available for routine clinical use, principally in oncology and transplantation. These underscore the potential of gene expression arrays and RNA sequencing for biomarker development, but this potential has not yet been fully realized and most candidates do not progress beyond the initial report. The first part of this review examines the process of gene expression- based biomarker development, highlighting how systematic biases and confounding can significantly skew study outcomes. Adequate validation in an independent cohort remains the single best means of protecting against these concerns. The second part considers gene-expression based biomarkers in Systemic Lupus Erythematosus (SLE) and systemic vasculitis. The type 1 interferon inducible gene signature remains by far the most studied in autoimmune rheumatic disease. While initially presented as an objective, blood-based biomarker of active SLE, subsequent research has shown that it is not specific to SLE and that its association with disease activity is considerably more nuanced than first thought. Nonetheless, it is currently under evaluation in ongoing trials of anti-interferon therapy. Other candidate markers of note include a prognostic CD8+ T-cell gene signature validated in SLE and ANCA-associated vasculitis, and a disease activity biomarker for SLE derived from modules of tightly correlated genes.

Immune- and ribosome-related genes were associated with systemic vasculitis.

This study aimed to investigate the molecular mechanism of systemic vasculitis via bioinformatics analysis. Gene express profile of E-GEOD-16945 (13 Takayasu arteritis samples and 13 control samples) was downloaded from European Bioinformatics Institute (EBI) database. Differentially expressed genes (DEGs) were screened between Takayasu arteritis and normal controls (|log FC| > 1). Basic local alignment search tool (BLASTX) was used for the Clusters of Orthologous Groups (COG) classification of DEGs. Gene ontology analysis was performed for the DEGs (P < 0.05). A gene expression network was built with DEGs. Mcode in Cytoscape software was used to extract modules from the network (degree ≥ 2, K-core ≥ 2 and adjusted P-value < 0.05) followed by pathway analysis using GenMAPP (false discovery rate < 0.05). A total of 747 DEGs were identified. There were 16 significant GO function terms enriched with DEGs, of which immune and defence response was the most significant GO term. Totally, three modules were extracted from gene expression network, including one module constituted with upregulated genes and two modules constituted with downregulated genes. Furthermore, human leucocyte antigen (HLA)-DRB1, HLA-DPA1, HLA-DPB1, HLA-DOA and HLA-DRA in the downregulated modules were significantly linked to immune-related pathways (intestinal immune network for IgA production and systemic lupus erythematosus pathways), while ribosomal protein L 31 (RPL31), RPS3A and RPL9 in the upregulated module were enriched in ribosome pathway. The immune-related pathways, ribosome pathway, immune-related genes including (HLA-DRB1, HLA-DPA1, HLA-DPB1, HLA-DOA and HLA-DRA) and ribosome-related genes (RPL31, RPS3A and RPL9) might be involved in systemic vasculitis.

Susceptibility quantitative trait loci for pathogenic leucocytosis in SCG/Kj mice, a spontaneously occurring crescentic glomerulonephritis and vasculitis model.

The spontaneous crescentic glomerulonephritis-forming/Kinjoh (SCG/Kj) mouse, a model of human crescentic glomerulonephritis (CrGN) and systemic vasculitis, is characterized by the production of myeloperoxidase-specific anti-neutrophil cytoplasmic autoantibody (MPO-ANCA) and marked leucocytosis. This study was performed to identify the specific populations of leucocytes associated with CrGN and susceptibility loci for pathogenic leucocytosis. Four hundred and twenty female (C57BL/6 × SCG/Kj) F2 intercross mice were subjected to serial flow cytometry examination of the peripheral blood (PB). Kidney granulocytes and monocytes were examined histopathologically. Linkage analyses were performed with 109 polymorphic microsatellite markers. Correlation studies revealed that increase of the granulocytes, F4/80(+) cells, CD3(+) CD4(-) CD8(-) T cells and dendritic cells (DCs) in peripheral blood (PB) were associated significantly with glomerulonephritis, crescent formation and vasculitis. In kidney sections, F4/80(low) cells were observed in crescent, while F4/80(high) cells were around the Bowman's capsules and in the interstitium. Numbers of F4/80(+) cells in crescents correlated significantly with F4/80(+) cell numbers in PB, but not with numbers of F4/80(+) cells in the interstitium. Genome-wide quantitative trait locus (QTL) mapping revealed three SCG/Kj-derived non-Fas QTLs for leucocytosis, two on chromosome 1 and one on chromosome 17. QTLs on chromosome 1 affected DCs, granulocytes and F4/80(+) cells, but QTL on chromosome 17 affected DCs and granulocytes. We found CrGN-associated leucocytes and susceptibility QTLs with their positional candidate genes. F4/80(+) cells in crescents are considered as recruited inflammatory macrophages. The results provide information for leucocytes to be targeted and genetic elements in CrGN and vasculitis.

Epidemiology and clinical features of systemic vasculitis.

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.

Is there a crossroad between infections, genetics, and Henoch-Schönlein purpura?

Henoch-Schönlein purpura is the most common systemic vasculitis in childhood, characterized by the presence of immunoglobulin A deposits in the small vessels of skin, gastrointestinal tube, joints and kidneys. Although there have been great efforts made in elucidating its pathogenic mechanisms, Henoch-Schönlein purpura etiology remains unknown: the basic scene comes across an abnormal inflammatory process deriving from immune reactions to various antigenic stimuli, which might be bacterial, viral, or parasitic agents, in a genetically prone individual. Then, a peculiar immune complex deposition in the vascular walls and overproduction of different proinflammatory molecules elicit different clinical signs, which might be differentiated according to either a specific trigger or a specific genetic make-up. The aim of this review is to make a critical appraisal of the last 15years' medical literature concerning the relationship between infections, genetics, and Henoch-Schönlein purpura in pediatrics.

The association of HLA-DRB1 alleles with antineutrophil cytoplasmic antibody-associated systemic vasculitis in Chinese patients.

Antineutrophil cytoplasmic antibody (ANCA)-associated systemic vasculitis (AASV) is a group of autoimmune diseases. The human leukocyte antigen (HLA) system is devoted to the pathogenesis of these autoimmune diseases. The present study aimed to investigate the distribution of HLA-DRB1 alleles in Chinese AASV patients and its potential association with clinical and pathologic characteristics. This study included 152 Chinese patients with AASV and 200 healthy controls. Typing of HLA-DRB1 alleles was performed by bidirectional sequencing of exon 2. Compared with normal controls, DRB1*1454 was significantly less prevalent in AASV patients (0/304 vs 14/400, p = 4.6 × 10(-4), p corrected (p(c)) = 0.017), whereas DRB1*1101 was significantly more frequent in patients with MPA (32/214 vs 26/400, p = 6.4 × 10(-4), p(c) = 0.023). In patients with Wegener's granulomatosis (WG) who were PR3-ANCA positive, DRB1*1202 (8/38 vs 20/400, p = 1.3 × 10(-3), p(c) = 0.047) was more prevalent than in normal controls. Compared with normal controls, HLA-DRB1*1454 was less prevalent in AASV patients, whereas DRB1*1101 was significantly more frequent in patients with microscopic polyangiitis. HLA-DRB1*1202 was prevalent among patients with PR3-ANCA-positive WG.