Genetics of vasculitis

Association between Tubulointerstitial Nephritis and Uveitis Syndrome and Small-Vessel CNS Vasculitis: A Case of Polyautoimmunity

INTRODUCTION

 We report a case study of two male pediatric patients presenting with anterior uveitis and elevated renal function parameters. Both were diagnosed with tubulointerstitial nephritis and uveitis syndrome and subsequently developed diffuse cerebral symptoms such as headache, fatigue, and diziness.

METHODS

 Magnetic resonance images (MRIs) of the brain showed T2-hyperintense lesions with and without gadolinium enhancement leading to brain biopsy and diagnosis of small-vessel central nervous system (CNS) vasculitis in both cases. Both patients were treated according to BrainWorks small-vessel vasculitis protocol and symptoms vanished over the course of treatment. Follow-up MRIs up to 12 months after initiation of therapy showed no signs of recurrence indicating a monophasic disease.

CONCLUSION

 Small-vessel CNS vasculitis can occur simultaneously to other autoimmune diseases (ADs) in the scope of polyautoimmunity. As clinical findings of CNS vasculitis are often unspecific, neurological symptoms in nonneurological ADs should be adressed thoroughly. Under suspicion of small-vessel CNS vasculitis brain biopsy is still the gold standard and only secure way of definitive diagnosis.

Three Diseases Mediated by Different Immunopathologic Mechanisms-ANCA-Associated Vasculitis, Anti-Glomerular Basement Membrane Disease, and Immune Complex-Mediated Glomerulonephritis-A Common Clinical and Histopathologic Picture: Rapidly Progressive Crescentic Glomerulonephritis

Immune mechanisms play an important role in the pathogenesis of glomerulonephritis (GN), with autoimmunity being the main underlying pathogenetic process of both primary and secondary GN. We present three autoimmune diseases mediated by different autoimmune mechanisms: glomerulonephritis in vasculitis mediated by anti-neutrophil cytoplasmic antibodies (ANCAs), glomerulonephritis mediated by anti-glomerular basement membrane antibodies (anti-GBM antibodies), and immune complex-mediated glomerulonephritis. Some of these diseases represent a common clinical and histopathologic scenario, namely rapidly progressive crescentic glomerulonephritis. This is a severe illness requiring complex therapy, with the main role being played by therapy aimed at targeting immune mechanisms. In the absence of immune therapy, the crescents, the characteristic histopathologic lesions of this common presentation, progress toward fibrosis, which is accompanied by end-stage renal disease (ESRD). The fact that three diseases mediated by different immunopathologic mechanisms have a common clinical and histopathologic picture reveals the complexity of the relationship between immunopathologic mechanisms and their clinical expression. Whereas most glomerular diseases progress by a slow process of sclerosis and fibrosis, the glomerular diseases accompanied by glomerular crescent formation can progress, if untreated, in a couple of months into whole-nephron glomerulosclerosis and fibrosis. The outcome of different immune processes in a common clinical and histopathologic phenotype reveals the complexity of the relationship of the kidney with the immune system. The aim of this review is to present different immune processes that lead to a common clinical and histopathologic phenotype, such as rapidly progressive crescentic glomerulonephritis.

Race and Gender on the Mortality of Giant Cell Arteritis in Hospitalized Patients: A 15-Year National Inpatient Study

BACKGROUND

Critical appraisal of mortality in giant cell arteritis (GCA) through a racial lens is imperative as gender and racial disparities remain a global healthcare concern.

OBJECTIVE

To analyze the impact of race and gender on the mortality of GCA in United States (US)-hospitalized patients.

METHODS

In this retrospective cohort study, the National Inpatient Sample (NIS) database from January 2003 to December 2018 was searched to identify all patients aged >18 years hospitalized with giant cell arteritis. Patients' baseline characteristics were summarized using descriptive statistics. Inferential statistics were done for categorical and continuous variables. Multivariate logistic regression, adjusting for patient and hospital-level cofounders was performed to find an association between race and outcomes of interest.

RESULTS

Over the 15-year study period, a total of 8,352 patients (72.7% White, 14.5% Black or African American, 7.6% Hispanic, 2.2% Asian, 0.4% Alaska Native, and 2.6% under-represented populations) were hospitalized for GCA. The mean age at diagnosis was 73.6 ± 0.12 years. Women represented 71.9% of GCA patients and had a lower risk of mortality (OR 0.463, 95% CI: 0.235 - 0.912, p <0.05). Patients with GCA were hospitalized for an average of 4.64 days ± 0.04 days and 0.55% died. The mortality rate was lowest in Black or African American (0.1%) populations and highest among Alaska Native patients (8%). Mortality was 68% lower in those who had temporal artery biopsy (OR 0.32, 95% CI: 0.16-0.64, p <0.05).

CONCLUSION

GCA disproportionally affected female patients, but mortality was higher in male patients. Alaska Native patients had the least number of hospitalizations but the highest in-hospital mortality rate. Black or African Americans had the lowest mortality rate.

Selective deficiency of UCP-1 and adropin may lead to different subtypes of anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic autoimmune disease that is prone to respiratory and renal failures. Its major target antigens are serine protease 3 (PR3) and myeloperoxidase (MPO), but the determinants of PR3 and MPO subtypes are still unclear. Uncoupling protein-1 (UCP-1) and adropin (Adr) regulate mutually and play an important role in endothelial cell injury. In this study, adropin and UCP-1 knockout (AdrKO and UCP-1-KO) models were established on the basis of C57BL/6 J mice. The results showed that UCP-1-KO and AdrKO mice similar to AAV: significant inflammatory cell infiltration, vascular wall damage, and erythrocyte extravasation. The pathological basis of AdrKO was that endothelial cells adhered and activated neutrophils to release MPO, and the core gene was peroxisome proliferator-activated receptor gamma (PPARG). However, UCP-1-KO induced PR3 release, and the accumulation and expression of tissue factor on the vascular wall, and the core gene was peroxisome proliferator-activated receptor delta (PPARD). The present study verified that the subtypes of AAV may be genetically different diseases and it also provide novel experimental evidence for clinical differentiation of the two subtypes.

Vasculopathy, Immunodeficiency, and Bone Marrow Failure: The Intriguing Syndrome Caused by Deficiency of Adenosine Deaminase 2

Deficiency of adenosine deaminase 2 (DADA2) is a monogenic form of systemic vasculopathy that often presents during early childhood. Linked to biallelic mutations in ADA2 (previously CECR1), DADA2 was initially described as a syndrome of recurrent fever, livedo racemosa, early-onset strokes, and peripheral vasculopathy that resembles polyarteritis nodosum. However, the wide spectrum of clinical findings and heterogeneity of disease, even among family members with identical mutations, is increasingly recognized. Evidence of systemic inflammation and vasculopathy is not uniformly present in DADA2 patients and some can remain asymptomatic through adulthood. Humoral immunodeficiency characterized by low immunoglobulin levels and increased risk of infection is another common feature of DADA2. Variable cytopenias including pure red cell aplasia that mimics Diamond-Blackfan anemia can also be primary manifestations of DADA2. How defects in a single gene translate into these heterogeneous presentations remains to be answered. In this review, we will summarize lessons learned from the pleiotropic clinical manifestations of DADA2.

HLA-DPB1 as a Risk Factor for Relapse in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis: A Cohort Study

OBJECTIVE

The antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) form a group of small-vessel vasculitides with systemic involvement. Although the etiology of AAVs remains largely unknown, both genetic and environmental factors have been implicated. Recently, certain alleles in the HLA-DPB1 region on chromosome 6 were shown to be associated with proteinase 3 (PR3)-ANCA-positive AAV but not with myeloperoxidase (MPO)-ANCA-positive AAV. The aim of this study was to investigate whether different alleles in the HLA-DPB1 region have clinical and/or prognostic implications in AAV.

METHODS

One hundred seventy-four patients with a diagnosis of AAV were recruited at the Maastricht University Medical Centre between 2000 and 2009. Seventeen different HLA-DPB1 alleles were determined using the restriction fragment length polymorphism technique. A validation cohort of 170 AAV patients from the Vasculitis Centre of Luebeck/Bad Bramstedt was included.

RESULTS

In the initial cohort, the distribution of HLA-DPB1 alleles was significantly different between PR3-ANCA-positive compared with MPO-ANCA-positive AAV patients, ANCA-negative AAV patients, and healthy controls. Importantly, HLA-DPB1*04:01 was present in 90% of PR3-ANCA-positive AAV patients compared with 63% of MPO-ANCA-positive AAV patients, 58% of ANCA-negative patients, and 63% of healthy controls. Patients homozygous for HLA-DPB1*04:01 had relapses more often compared with heterozygous patients and noncarrier patients. This association persisted after correction for ANCA subtype and diagnosis. In the validation cohort, patients homozygous for HLA-DPB1*04:01 and those heterozygous for HLA-DPB1*04:01 had relapses more often compared with noncarrier patients. When both patient cohorts were merged (n = 344), homozygous patients relapsed most often, followed by heterozygous patients and noncarrier patients.

CONCLUSION

Carriage of HLA-DPB1*04:01 in patients with AAV is significantly associated with an increased risk of relapse compared with HLA-DPB1*04:01-negative patients, irrespective of ANCA status or clinical AAV entity.

Genetic variants in ANCA-associated vasculitis: a meta-analysis

BACKGROUND

Genetic factors may influence the pathogenic pathways leading to antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). We performed a meta-analysis to determine the genetic variants most likely associated with AAV and investigated whether diagnostic and serological subtypes within AAV have distinct genetic backgrounds.

METHODS

Studies investigating the association between genetic variants and AAV in humans were searched in PubMed, EMBASE and Web of Science. All variants investigated in at least two studies were selected. Subsequently, all studies assessing these variants were included in this meta-analysis. Additionally, data on these variants from the largest genome-wide association studies in AAV were included to increase the validity of this meta-analysis.

RESULTS

The literature search yielded 5180 articles. 62 articles investigating 140 genetic variants were included, 33 of which were associated with AAV in a meta-analysis. These genetic variants were in or near the following genes: CD226, CTLA-4, FCGR2A, HLA-B, HLA-DP, HLA-DQ, HLA-DR, HSD17B8, IRF5, PTPN22, RING1/RXRB, RXRB, STAT4, SERPINA1 and TLR9. Moreover, we identified genetic distinctions between granulomatosis with polyangiitis and microscopic polyangiitis and between proteinase 3 ANCA vasculitis and myeloperoxidase ANCA vasculitis. In 76% of the genetic variants, subdivision based on ANCA serotype resulted in higher ORs than subdivision based on clinical diagnosis.

CONCLUSIONS

This meta-analysis identified 33 genetic variants associated with AAV, supporting a role for alpha-1-antitrypsin, the major histocompatibility complex system, and several distinct inflammatory processes in AAV pathogenesis. Our results indicate that subdivision of AAV based on ANCA serotype has a stronger genetic basis than subdivision based on clinical diagnosis.

Enho Mutations Causing Low Adropin: A Possible Pathomechanism of MPO-ANCA Associated Lung Injury

BACKGROUND

Myeloperoxidase (MPO) anti-neutrophil cytoplasm autoantibody (ANCA)-associated vasculitis commonly causes life-threatening pulmonary alveolar hemorrhage or fibrosis. Only a limited number of candidate gene variants have been explored, but hitherto, are not widely confirmed. In the present study, we investigated the importance of energy homeostasis associated gene (Enho) mutations and adropin deficiency in the development of MPO-ANCA associated lung injury.

METHODS

We analyzed the peripheral blood mononuclear cells from 152 unrelated patients and 220 population-matched healthy individuals for genetic variations in Enho. Functional studies with adropin knockout (AdrKO) on C57BL/6J mice were also performed.

FINDINGS

Sequencing revealed six patients with p.Ser43Thr and that five patients shared Cys56Trp amino acid substitution in Enho. Serum concentration of adropin was significantly lower in patients than that of the healthy subjects (P<0.0001), especially those with Enho mutations. In vivo, homo- and heterozygous carriers of the null adropin allele exhibited MPO-ANCA associated pulmonary alveolar hemorrhage as compared to wild-type mice. AdrKO mice exhibit reduced eNOS (Ser1177) and Akt1 (Ser473) phosphorylation and loss of Treg cells.

INTERPRETATION

Our findings indicate that the presence of Enho mutations or adropin-deficiency is a probable molecular basis for the initial events triggered in MPO-ANCA associated lung injury.

Meta-Analysis of Associations Between Interleukin-10 Polymorphisms and Susceptibility to Vasculitis

OBJECTIVE

This study determined whether interleukin-10 (IL-10) polymorphisms are associated with susceptibility to vasculitis.

METHODS

A meta-analysis was conducted of the associations between the IL-10 -1082 G/A, -819 C/T, and -592 C/A polymorphisms and the haplotype of the IL-10-1082 G/A, -819 C/T, -592 C/A polymorphisms and vasculitis.

RESULTS

A total of 21 comparative studies involving 4121 patients and 5504 controls were considered in the meta-analysis. Meta-analysis revealed no association between the IL-10-1082 G allele and vasculitis in all study subjects (OR = 0.927, 95% CI = 0.780-1.102, p = 0.389). However, disease-specific meta-analysis showed an association between Wegener's granulomatosis (WG) and the IL-10-1082 G allele (OR = 0.729, 95% CI = 0.547-0.971, p = 0.031). Meta-analysis revealed an association between vasculitis and the IL-10-819 C allele (OR = 0.804, 95% CI = 0.706-0.916, p = 0.001) in all study subjects and Behcet's disease (BD) (OR = 0.724, 95% CI = 0.679-0.781, p < 1.0 × 10(-9)). Meta-analysis of the IL-10-592 C allele showed an association with vasculitis in all study subjects (OR = 0.805, 95% CI = 0.619-0.938, p = 0.005) and BD (OR = 0.718, 95% CI = 0.661-0.781, p < 1.0 × 10(-9)). Meta-analysis of the IL-10 haplotype revealed an association between the GCC haplotype and vasculitis in Europeans (OR = 1.239, 95% CI = 1.105-1.513, p = 0.035).

CONCLUSIONS

This meta-analysis showed that IL-10 polymorphisms are associated with vasculitis susceptibility, especially in WG and BD.

What matters for patients with vasculitis?

Advances in clinical care for patients with vasculitis have improved survival rates and created new challenges related to the ongoing management of chronic disease. Lack of curative therapies, burden of disease, treatment-related side effects, and fear of relapse contribute to patient-perceived reduction in quality of life. Patient-held beliefs about disease and priorities may differ substantially from the beliefs of their health care providers, and research paradigms are shifting to reflect more emphasis on understanding vasculitis from the patient's perspective. Efforts are ongoing to develop disease outcome measures in vasculitis that better represent the patient experience. Health care providers who care for patients with vasculitis should be sensitive to the substantial burdens of disease commonly experienced by patients living with the disease and should strive to provide comprehensive care directed towards the medical and biopsychological needs of these patients.

Proteinase 3-ANCA Vasculitis versus Myeloperoxidase-ANCA Vasculitis

In patients with GN or vasculitis, ANCAs are directed against proteinase 3 (PR3) or myeloperoxidase (MPO). The differences between PR3-ANCA-associated vasculitis (AAV) and MPO-AAV described in the past have been supplemented during the last decade. In this review, we discuss the differences between these two small-vessel vasculitides, focusing especially on possible etiologic and pathophysiologic differences. PR3-AAV is more common in northern parts of the world, whereas MPO-AAV is more common in southern regions of Europe, Asia, and the Pacific, with the exception of New Zealand and Australia. A genetic contribution has been extensively studied, and there is a high prevalence of the HLA-DPB1*04:01 allele in patients with PR3-AAV as opposed to patients with MPO-AAV and/or healthy controls. Histologically, MPO-AAV and PR3-AAV are similar but show qualitative differences when analyzed carefully. Clinically, both serotypes are difficult to distinguish, but quantitative differences are present. More organs are affected in PR3-AAV, whereas renal limited vasculitis occurs more often in patients with MPO-AAV. For future clinical trials, we advocate classifying patients by ANCA serotype as opposed to the traditional disease type classification.

Genetic Susceptibility to ANCA-Associated Vasculitis: State of the Art

ANCA-associated vasculitis (AAV) is a group of disorders that is caused by inflammation affecting small blood vessels. Both arteries and veins are affected. AAV includes microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA) renamed from Wegener’s granulomatosis, and eosinophilic granulomatosis with polyangiitis (EGPA), renamed from Churg–Strauss syndrome. AAV is primarily due to leukocyte migration and resultant damage. Despite decades of research, the mechanisms behind AAV disease etiology are still not fully understood, although it is clear that genetic and environmental factors are involved. To improve the understanding of the disease, the genetic component has been extensively studied by candidate association studies and two genome-wide association studies. The majority of the identified genetic AAV risk factors are common variants. These have uncovered information that still needs further investigation to clarify its importance. In this review, we summarize and discuss the results of the genetic studies in AAV. We also present the novel approaches to identifying the causal variants in complex susceptibility loci and disease mechanisms. Finally, we discuss the limitations of current methods and the challenges that we still have to face in order to incorporate genomic and epigenomic data into clinical practice.

The immunopathology of ANCA-associated vasculitis

The small-vessel vasculitides are a group of disorders characterised by variable patterns of small blood vessel inflammation producing a markedly heterogeneous clinical phenotype. While any vessel in any organ may be involved, distinct but often overlapping sets of clinical features have allowed the description of three subtypes associated with the presence of circulating anti-neutrophil cytoplasmic antibodies (ANCA), namely granulomatosis with polyangiitis (GPA, formerly known as Wegener’s Granulomatosis), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (eGPA, formerly known as Churg-Strauss syndrome). Together, these conditions are called the ANCA-associated vasculitidies (AAV). Both formal nomenclature and classification criteria for the syndromes have changed repeatedly since their description over 100 years ago and may conceivably do so again following recent reports showing distinct genetic associations of patients with detectable ANCA of distinct specificities. ANCA are not only useful in classifying the syndromes but substantial evidence implicates them in driving disease pathogenesis although the mechanism by which they develop and tolerance is broken remains controversial. Advances in our understanding of the pathogenesis of the syndromes have been accompanied by some progress in treatment, although much remains to be done to improve the chronic morbidity associated with the immunosuppression required for disease control.

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.

Relation between asymptomatic proteinase 3 antibodies and future granulomatosis with polyangiitis

BACKGROUND AND OBJECTIVES

The subclinical pathogenesis of granulomatosis with polyangiitis (GPA) has not been completely elucidated. Proteinase 3 (PR3) antibodies are strongly associated with GPA, but have not been evaluated before disease presentation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a retrospective case-control serum bank study in which PR3 antibodies and C-reactive protein (CRP) in up to three longitudinal serum samples for 27 GPA patients before diagnosis (1 day-19 years) were compared with 27 controls whose serum samples were matched for age, sex, and race. This study analyzed all patients with American College of Rheumatology criteria-confirmed disease identified in the Department of Defense electronic medical records between 1990 and 2008.

RESULTS

A greater percentage of GPA patients had at least one elevated PR3 antibody level (≥6 U/ml) as well as at least one detectable PR3 antibody level (>1 U/ml) before diagnosis compared with matching controls (63% [17 of 27] versus 0% [0 of 27], P<0.001; and 85% [23 of 27] versus 4% [1 of 27], P<0.001, respectively). A greater percentage of GPA patients had a >1 U/ml per year rate of increase in PR3 antibody level compared with matching controls (62% [21 of 26] versus 0% [0 of 26], P<0.001). PR3 antibody more frequently became elevated before CRP (67% [12 of 18] versus 33% [6 of 18], P=0.04).

CONCLUSIONS

Subclinical PR3 antibody presence, trajectory, and temporal relationship to CRP associates with the future diagnosis of GPA. This data set further elucidates the pathogenesis of GPA.

Vasculitic neuropathy

Vasculitis is a primary phenomenon in autoimmune diseases such as polyarteritis nodosa, Wegener's granulomatosis, Churg-Strauss syndrome, microscopic polyangiitis, and essential mixed cryoglobulinemia. As a secondary feature vasculitis may complicate, for example, connective tissue diseases, infections, malignancies, and diabetes. Vasculitic neuropathy is a consequence of destruction of the vessel wall and occlusion of the vessel lumen of small epineurial arteries. Sometimes patients present with nonsystemic vasculitic neuropathy, i.e., vasculitis limited to peripheral nerves and muscles with no evidence of further systemic involvement. Treatment with corticosteroids, sometimes in combination with other immunosuppressants, is required to control the inflammatory process and prevent further ischemic nerve damage.

Genetically distinct subsets within ANCA-associated vasculitis

BACKGROUND

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a severe condition encompassing two major syndromes: granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis) and microscopic polyangiitis. Its cause is unknown, and there is debate about whether it is a single disease entity and what role ANCA plays in its pathogenesis. We investigated its genetic basis.

METHODS

A genomewide association study was performed in a discovery cohort of 1233 U.K. patients with ANCA-associated vasculitis and 5884 controls and was replicated in 1454 Northern European case patients and 1666 controls. Quality control, population stratification, and statistical analyses were performed according to standard criteria.

RESULTS

We found both major-histocompatibility-complex (MHC) and non-MHC associations with ANCA-associated vasculitis and also that granulomatosis with polyangiitis and microscopic polyangiitis were genetically distinct. The strongest genetic associations were with the antigenic specificity of ANCA, not with the clinical syndrome. Anti-proteinase 3 ANCA was associated with HLA-DP and the genes encoding α(1)-antitrypsin (SERPINA1) and proteinase 3 (PRTN3) (P=6.2×10(-89), P=5.6×10(-12,) and P=2.6×10(-7), respectively). Anti-myeloperoxidase ANCA was associated with HLA-DQ (P=2.1×10(-8)).

CONCLUSIONS

This study confirms that the pathogenesis of ANCA-associated vasculitis has a genetic component, shows genetic distinctions between granulomatosis with polyangiitis and microscopic polyangiitis that are associated with ANCA specificity, and suggests that the response against the autoantigen proteinase 3 is a central pathogenic feature of proteinase 3 ANCA-associated vasculitis. These data provide preliminary support for the concept that proteinase 3 ANCA-associated vasculitis and myeloperoxidase ANCA-associated vasculitis are distinct autoimmune syndromes. (Funded by the British Heart Foundation and others.).

The Molecular Biology and Treatment of Systemic Vasculitis in Children

Primary systemic vasculitides are rare in childhood but are associated with significant morbidity and mortality. The cause of the majority of vasculitides is unknown, although it is likely that a complex interaction between environmental factors, such as infections and inherited host responses, triggers the disease and determines the vasculitis phenotype. Several genetic polymorphisms in vasculitides have now been described, which may be relevant in terms of disease predisposition or development of disease complications. Treatment regimens continue to improve with the use of different immunosuppressive medications and newer therapeutic approaches such as biologic agents. This chapter reviews recent studies shedding light on the pathogenesis of vasculitis with emphasis on molecular biology where known, and summarizes current treatment strategies. We discuss new emerging challenges particularly with respect to the long-term cardiovascular morbidity for children with systemic vasculitis and emphasize the importance of future international multicenter collaborative studies to further increase and standardize the scientific base investigating and treating childhood vasculitis.

[The genetics of vasculitides]

Genetic association studies have been of great value in the past by contributing to the understanding of pathophysiological mechanisms of chronic inflammatory and autoimmune diseases. Many genetic risk factors have been identified which confer susceptibility for one or several (autoimmune) disease(s). Using a candidate-gene approach, the first genetic risk factors and polymorphisms of vasculitides have been identified. Due to the rarity of autoimmune vasculitides often only small sample numbers have been generated and analysed, leading to inconsistent results. Furthermore, differences in ethnic background may complicate analysis. Only few of the detected risk factors have been reliably replicated in larger cohorts, such as the association of the PTPN22*620W allele with WG and MPA, the deficiency allele Pi*Z of the alpha1 antitrypsin gene and the HLA-DPB*04041 allele with WG and the HLA-DRB3/DRB4 with CSS. Genome-wide association studies (GWAS) offer the advantage of screening the whole genome for risk factors rather than relying on disease models postulated by the investigator; however, they require even larger sample sizes. Initial results from GWA studies are available for Behçet's disease and Kawasaki syndrome, which identified new genetic associations but require replication, especially since some of the identified risk factors could not be linked to pathophysiological pathways to date.