Trojan horses: drug culprits associated with antineutrophil cytoplasmic autoantibody (ANCA) vasculitis

Treatment strategies for ANCA-associated vasculitides: from standard protocols to future horizons

INTRODUCTION

ANCA-associated vasculitides (AAV), classified into granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis represent a group of disorders characterized by necrotizing vasculitis of small vessels, endothelial injury and tissue damage. The outcomes and prognosis of AAV have undergone significant changes with the introduction of glucocorticoids (GCs) and other immunosuppressants (cyclophosphamide, azathioprine, methotrexate, and mycophenolate mofetil). The enhanced understanding of pathogenesis has subsequently led to the incorporation into clinical practice of drugs targeting specific therapeutic targets.

AREAS COVERED

After an extensive literature search of Pubmed, Medline, Embase of the most recent evidence, we provide an overview of available treatments, highlighting how newer drugs have integrated into standard protocols. Our review also explores potential new therapeutic targets, including B cell depletion and inhibition, T cell inhibition, complement inhibition, and IL-5 and IgE inhibition.

EXPERT OPINION

There is hope that the new treatment targets currently under study in AAV may enable a faster and more lasting clinical response, ensuring the reduction of possible side effects from therapies. Moreover, numerous aspects necessitate further exploration in the future, such as tailoring of GCs, integration of GCs-sparing agents, efficacy of combination therapy, optimal maintenance therapy, to reduce organ-damage and improve quality of life.

ANCA-Associated Vasculitis

ANCA-associated vasculitis (AAV) is a necrotizing, small-to-medium vessel vasculitis associated with significant morbidity and mortality. AAV is a systemic autoimmune disease affecting kidneys, eyes, sinuses, peripheral nerves, skin, and upper and lower respiratory tracts. AAV tends to present in characteristic phenotypes categorized clinically as granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic GPA (EGPA). Kidney involvement is a common feature of AAV, and has important implications on disease prognosis and management. Existing therapies have been refined and improvements in our understanding of the pathophysiology of AAV has led to approval of novel therapies. In this review, we provide an overview of epidemiology, disease mechanisms, clinical presentation and review therapeutic strategies for induction and maintenance of remission.

[Secondary vasculitides]

Vasculitides that occur in association with underlying primary diseases are called secondary vasculitides. In the diverse differential diagnostics of vasculitides, a large variety of secondary vasculitides have to be considered. Secondary vasculitides cover the full spectrum of vasculitides, presenting in manifold clinical manifestations. This article provides an overview of systemic diseases and etiological factors, such as infections, drugs, and malignancies, which can be associated with vasculitides. The possible associations with infectious agents are too numerous to be comprehensively covered and are discussed in an exemplary fashion and with a western European focus. Especially in atypical and refractory disease courses, a secondary vasculitis should be considered. In light of the diversity of differential diagnoses and the particular challenges posed by secondary vasculitides, interdisciplinary collaboration is the key for an accurate and early diagnosis as well as for successful treatment management. Treatment of the primary disease should always be prioritized and, if a drug-induced vasculitis is suspected, immediate cessation of the culprit drug is mandatory.

ANCA-Associated Vasculitis: Practical Issues in Management

ANCA associated vasculitides are multi-system autoimmune diseases which are increasing in prevalence. In this review we will discuss the clinical manifestations and review the management options. We highlight the various trials of induction and maintenance therapy and discuss the areas of unmet need. These include understanding which patients are at highest risk of relapse, clinical adaptation of improved biomarkers of disease activity and tools to discuss long term prognosis.

Unilateral Diffuse Alveolar Hemorrhage as an Initial Presentation of Microscopic Polyangiitis

Diffuse alveolar hemorrhage (DAH) is a life-threatening condition due to widespread damage to small pulmonary vessels commonly caused by systemic vasculitis. Alveolar involvement is typically multi-lobar and bilateral. It frequently presents as bilateral diffuse airspace opacities on chest imaging. Unilateral DAH is rare. Patients presenting with hemoptysis, anemia, hypoxemia, progressive dyspnea, and opacities on chest imaging should be evaluated for systemic vasculitis such as antineutrophilic cytoplasmic antibody (ANCA) vasculitis. We report the case of a 23-year-old female who presented with hemoptysis, severe dyspnea, hypoxemia, anemia, and oliguria. The laboratory exam results showed the patient to be p-ANCA positive, which suggests a diagnosis of microscopic polyangiitis. Chest X-ray showed unilateral airspace opacities, and DAH was confirmed by hemosiderin-laden macrophages on bronchoalveolar fluid histopathological examination. After treatment with plasmapheresis, intravenous methylprednisolone pulse, and cyclophosphamide, the patient's symptoms and radiographic findings improved.

A Rare Case of Hydralazine-Induced Diffuse Alveolar Hemorrhage

Hydralazine-induced anti-neutrophil cytoplasmic antibody (ANCA) vasculitis may occur any time after hydralazine initiation. General internists should recognize diffuse alveolar hemorrhage (DAH) as a rare complication of this condition, as early treatment reduces the associated high risk of mortality. We describe the case of an 82-year-old female with diastolic heart failure who presented with a one-month history of worsening dyspnea on exertion and a one-week history of scant hemoptysis and fatigue. Her medications included aspirin and hydralazine. She was hypoxic with bilateral expiratory wheezes on exam. Labs showed new anemia, elevated creatinine, proteinuria, and hematuria. Chest computed tomography showed asymmetric bilateral upper lobe ground-glass attenuation superimposed on interlobular septal thickening and intralobular lines. Further testing showed anti-nuclear antibody, positive ANCA, perinuclear ANCA (p-ANCA), and anti-myeloperoxidase ANCA (anti-MPO-ANCA). Renal biopsy revealed MPO-ANCA, pauci-immune, necrotizing, and crescentic glomerulonephritis. She was diagnosed with DAH secondary to hydralazine-induced ANCA-associated vasculitis (AAV). Hydralazine is an anti-hypertensive medication with known potential for autoimmune reactions. Of these, AAV is a rare sequela mediated by anti-MPO and most commonly affects the kidneys. In rare circumstances, patients with AAV can develop pulmonary-renal syndrome, resulting in both glomerulonephritis and DAH with an associated high risk of mortality. Diagnosis requires a high index of suspicion in patients with acute kidney injury of unclear etiology. Early diagnosis through immune work-up and kidney biopsy should be pursued, as prompt recognition of the vasculitis, cessation of hydralazine, immunosuppression, and early plasma exchange are essential to an improved prognosis.

Diagnostic dilemma: drug-induced vasculitis versus systemic vasculitis

Drug-induced vasculitis can rarely cause inflammation and necrosis of blood vessel walls of both kidney and lung tissue. Diagnosis is challenging because of the lack of difference between systemic and drug-induced vasculitis in clinical presentation, immunological workup and pathological findings. Tissue biopsy guides diagnosis and treatment. Pathological findings must be correlated with clinical information to arrive at a presumed diagnosis of drug-induced vasculitis. We present a patient with hydralazine-induced antineutrophil cytoplasmic antibodies-positive vasculitis with a pulmonary-renal syndrome manifesting as pauci-immune glomerulonephritis and alveolar haemorrhage.

Focal Alveolar Hemorrhage Secondary to Hydralazine-Associated Antineutrophilic Cytoplasmic Antibody Vasculitis

Hydralazine is rarely associated with antineutrophilic cytoplasmic antibody (ANCA) vasculitis. In the appropriate clinical scenario, such as in a patient with pulmonary, renal, or cutaneous manifestations, finding antibodies against nuclear and cytoplasmic neutrophil antigens may suggest drug-induced vasculitis after exposure to hydralazine. We present the case of an elderly man diagnosed with focal alveolar hemorrhage with elevated concentrations of anti-myeloperoxidase antibody, anti-proteinase-3 antibody, and antinuclear antibodies in the setting of prolonged hydralazine therapy. We observed a rapid clinical improvement with hydralazine discontinuation and systemic corticosteroids. We did not observe further disease activity while on mycophenolate mofetil six months later.

Kidney Biopsy Findings in Patients with SARS-CoV-2 Infection or After COVID-19 Vaccination

BACKGROUND

Emerging case series described a temporal association between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and de novo or relapsing kidney diseases. We aimed to further understand vaccination- and coronavirus disease 2019 (COVID-19)-associated kidney diseases.

METHODS

We present findings from native kidney biopsies of patients recently vaccinated against SARS-CoV-2 ( n =27) and those with COVID-19 ( n =15), reviewed at a single German center. Diagnoses were compared among all native kidney biopsies ( n =10,206) obtained between the prepandemic (2019), pandemic (2020), and vaccination periods (2021) to determine whether there was an increase in kidney diseases in the observed periods.

RESULTS

Biopsy indication was increased serum creatinine and/or new-onset proteinuria. Glomerulopathies (20/27, 74%) were more common than tubulointerstitial diseases in postvaccination patients, with necrotizing GN (8/27, 30%) and primary podocytopathies and other GN types (6/27, 22% each) the most common forms. Acute tubular injury was the most common kidney disease in patients with COVID-19, followed by thrombotic microangiopathy (TMA) and necrotizing GN. The postvaccination and COVID-19 infection groups had similar kidney function recovery rates (69% and 73%, respectively). Furthermore, the frequencies of necrotizing GN, pauci-immune GN, TMA, or primary podocytopathies at our center did not increase between 2019 and 2021.

CONCLUSIONS

We observed differences in entity frequencies between the SARS-CoV-2 vaccination or COVID-19 groups, with glomerulopathies being more common in patients after vaccination and tubulointerstitial diseases in patients with COVID-19. Cases of TMA were observed only in the COVID-19 group. We detected no increase in the frequency of necrotizing GN, TMA, or podocytopathies between 2019 and 2021.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Kidney Histopathology After COVID-19 and SARS-CoV-2 Vaccination, NCT05043168.

PODCAST

This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/CJASN/2023_05_08_CJN0000000000000106.mp3.

Oral manifestations of anti-neutrophil cytoplasmic antibody-associated vasculitis: an update and narrative review of the literature

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is a multisystem disorder of small blood vessels subdivided into granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). Oral manifestations (OMs) have been reported to include mucosal ulceration, gingival enlargement, alveolar bone necrosis, tooth loss, oro-antral communication, palatal perforation, parotitis, and candidal infection mainly in GPA. They may appear during the course of the disease, as a disease flare-up, or as the presenting sign. These OMs are often nonspecific and can mimic an array of conditions, therefore formulating a differential diagnosis can be challenging. This review updates the OMs of GPA, and, for the first, time includes OMs of other AAVs. It provides recommendations for the overall assessment and the diagnosis and management of all AAV OMs with considerations for treatment coordination. The role of oral health care providers in multidisciplinary care is highlighted.

Vaskulitis mimics

Idiopathische Vaskulitiden sind seltene entzündliche Systemerkrankungen, die nach der Chapel-Hill Konsensus-Nomenklatur nach der Größe der prädominant betroffenen Gebiete von Blutgefäßen (große, mittelgroße, kleine Gefäße und Gefäße variabler Größe) eingeteilt werden. Vaskulitis mimics sind Syndrome, die ein ähnliches klinisches Bild hervorrufen oder leicht mit einer idiopathischen Vaskulitis verwechselt werden und teils sogar ein Krankheitsbild, das klinisch und histologisch einer Vaskulitis gleicht, auslösen können. Die Zahl der Vaskulitis mimics ist groß, je nach betroffenem Gefäßgebiet kommen hereditäre Erkrankungen des Bindegewebes, genetisch bedingte Immundefekt- und Autoinflammationssyndrome, infektiöse Erkrankungen, seltene entzündliche Systemerkrankungen, Tumorerkrankungen, medikamenteninduzierte Syndrome und zahlreiche weitere infrage. In diesem Review wird eine Auswahl klassischer Imitatoren von Vaskulitiden, orientiert an der Größe der betroffenen Blutgefäße präsentiert und Konstellationen, die typische „Fallstricke“ in der klinischen Abklärung darstellen können, diskutiert.

Overlapping Syndromes: Drug-Induced Vasculitis From Hydralazine With Positive Antinuclear Antibodies

Hydralazine is an antihypertensive medication that has been associated with drug-associated autoimmune syndromes like interstitial lung disease, pauci-immune glomerulonephritis, and hypocomplementemia. Hydralazine-induced ANCA-associated vasculitis and hydralazine induced positive antinuclear antibodies are rare. Clinical manifestations range from arthralgia, petechiae, or rash to multiorgan involvement. When presented as pulmonary-renal syndrome, it can be rapidly progressive and fatal. Here, we describe a case of hydralazine-associated vasculitis with rapidly progressive glomerulonephritis and highlight the importance of early diagnosis and prompt treatment.

The Utility of Bronchoscopy in Hydralazine-Induced ANCA-Associated Vasculitis

Hydralazine is a vasodilator used for the management of hypertension, heart failure, and hypertensive emergencies in pregnancy. It has been implicated in the causation of drug-induced lupus erythematosus (DLE) and rarely with ANCA-associated vasculitis (AAV), which may present as a pulmonary-renal syndrome and be rapidly fatal. Herein, we describe a case of hydralazine-associated AAV presenting as acute kidney injury with the use of early bronchoalveolar lavage (BAL) with serial aliquots to aid with diagnosis. Our case highlights how, in the correct clinical setting, BAL can act as a rapid diagnostic test to help guide quicker treatment to allow for better patient outcomes.

Caspase-8 activation in neutrophils facilitates autoimmune kidney vasculitis through regulating CD4+ effector memory T cells

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are closely associated with neutrophil recruitment and activation, but the impact of the neutrophil apoptosis process in autoimmune disease has been rarely explained. Here, by integrating and analyzing single-cell transcriptome datasets, we found that the caspase-8-associated pathway in neutrophils was highly activated in the kidney rather than in the blood. To verify the function of caspase-8 in neutrophils on AAVs progression, we constructed neutrophil-specific caspase-8 knockout mice combined with an AAVs model induced by human ANCA from AAVs patients, a rapid and powerful model developed in this study. Our results show that caspase-8 activation of neutrophils up-regulates the expression of several inflammatory and immunoregulatory factors, especially IL23A, regulating the activation and differentiation of tissue-resident CD4⁺ effector memory T cells. This study reveals that the activation of caspase-8 in neutrophils can worsen glomerulonephritis of AAVs by regulating inflammation and immunity.

Diagnosing and treating ANCA-associated vasculitis: an updated review for clinical practice

ANCA-associated vasculitides (AAV) are a group of rare, primary, systemic necrotizing small-vessel vasculitides. Granulomatosis with polyangiitis and microscopic polyangiitis account for ∼80–90% of all AAV. Exposure to silica dust, farming and chronic nasal Staphylococcus aureus carriage are associated with increased risk of developing AAV. When a diagnosis of AAV is suspected, as in patients with multisystem organ dysfunction or those with features such as chronic recurrent rhinosinusitis, cavitated lung nodules, palpable purpura or acute kidney injury, then appropriate further investigations are needed, including ANCA testing. In this scenario, a structured clinical assessment should be conducted, evaluating all the organs possibly involved, and tissue biopsy may be necessary for confirmation of the diagnosis. Therapeutic algorithms vary based on the severity of AAV, the clinical diagnosis/ANCA specificity, and the patient’s age, weight, comorbidities and prognosis. Recent data favour rituximab as a preferable option for both induction and maintenance of remission. In addition, regimens with less glucocorticoids are equally effective and safer in inducing remission compared with conventional regimens, and avacopan is an effective glucocorticoid-sparing option. In contrast, there is not compelling evidence to support the routine use of plasma exchange in addition to standard remission-induction therapy in AAV. ANCA and other biomarkers can be helpful in association with clinical assessment to guide diagnosis and treatment decisions. Patients should be frequently evaluated during follow-up for possible disease relapses or treatment-related morbidity, and for monitoring damage accrual, especially metabolic and cardiovascular damage.

Serum ANCA as Disease Biomarkers: Clinical Implications Beyond Vasculitis

Usually associated with autoimmune diseases, anti-neutrophil cytoplasmic antibodies are also detected in other conditions, such as infections, malignancies, and after intake of certain drugs. Even if the mechanisms of production and their pathogenic role have not been fully elucidated yet, ANCA are widely recognized as a clinically alarming finding due to their association with various disorders. While ANCA target several autoantigens, proteinase-3, and myeloperoxidase are the ones proved to be most frequently related to chronic inflammation and tissue damage in murine models. Albeit these autoantibodies could be present as an isolated observation without any implications, ANCA are frequently used in clinical practice to guide the diagnosis in a suspect of small vessel vasculitis. Conditions that should prompt the clinician to test ANCA status range from various forms of lung disease to renal or peripheral nervous system impairment. ANCA positivity in the presence of an autoimmune disease, especially rheumatoid arthritis, or connective tissue diseases, is frequently correlated with more clinical complications and treatment inefficacy, even in the absence of signs of vasculitis. For this reason, it has been postulated that ANCA could represent the final expression of an immune dysregulation rather than a pathogenic event responsible for organs damage. Recently, it has also been proposed that ANCA specificity (PR3 or MPO) could possibly define ANCA-associated vasculitides better than clinical phenotype. This review aims at summarizing the latest advancements in the field of ANCA study and clinical interpretation.

A Spotlight on Drug-Induced Vasculitis

PURPOSE OF REVIEW

Drug-induced vasculitis (DIV) is a rare form of vasculitis related to the use of various drugs. DIV primarily affects small to medium size vessels, but it can potentially involve vessels of any size. Differentiating between primary systemic vasculitis and DIV can be challenging; however, it is crucial, so that the offending agent can be discontinued promptly.

RECENT FINDINGS

The clinical phenotype of DIV is protean and depends on the size of the affected vessels. It ranges from arthralgias, to an isolated cutaneous rash, to severe single or multi-organ involvement. While withdrawal of the offending drug is the most important step in management, a significant number of patients require immunosuppressive therapy for varying periods of time. DIV can affect any vascular bed size, leading to protean vasculitic syndromes. Increased awareness among general practitioners, specialty, and subspecialty physicians is crucial for early recognition, and withdrawal of drug for better outcomes.

The presentation, etiologies, pathophysiology, and treatment of pulmonary renal syndrome: A review of the literature

Pulmonary renal syndrome (PRS) is a constellation of different disorders that cause both rapidly progressive glomerulonephritis and diffuse alveolar hemorrhage. While antineutrophil cytoplasmic antibody associated vasculitis and anti-glomerular basement membrane disease are the predominant causes of PRS, numerous other mechanisms have been shown to cause this syndrome, including thrombotic microangiopathies, drug exposures, and infections, among others. This syndrome has high morbidity and mortality, and early diagnosis and treatment is imperative to improve outcomes. Treatment generally involves glucocorticoids and immunosuppressive agents, but treatment targeted to the underlying disorder can improve outcomes and mitigate side effects. Familiarity with the wide range of possible causes of PRS can aid the clinician in workup, diagnosis and early initiation of treatment. This review provides a summary of the clinical presentation, etiologies, pathophysiology, and treatment of PRS.

Rare complication of a commonly used antihypertensive agent: A case of hydralazine-induced ANCA-associated vasculitis presenting as rapidly progressive glomerulonephritis

Hydralazine-induced ANCA-associated vasculitis is a rare clinical entity, with complications including rapidly progressive glomerulonephritis, pulmonary hemorrhage, and pulmonary-renal syndrome. We present this case to highlight the clinical features that support this challenging diagnosis and to emphasize the importance of prompt recognition and aggressive intervention given its significant morbidity and mortality.

Fulminant Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis After 10 Years of Hydralazine Use

Vasculitis, by definition, causes changes in the walls of blood vessels, including thickening, weakening, narrowing, and scarring, leading to inflammation and necrosis of the blood vessel walls. Small-vessel vasculitis is commonly associated with anti-neutrophil cytoplasmic antibodies (ANCA), which activate cytokine-primed neutrophils and monocytes that express ANCA antigens proteinase 3 (PR3) and myeloperoxidase (MPO) on their surface. The continuous injury and inflammation of these small vessels characterized by circulating immune complexes and antinuclear antibodies result in clinical features standard in all types of vasculitis. When a 59-year-old male with a history of heart failure, hypertension (on hydralazine 100 mg every eight hours for more than ten years), diabetes mellitus, and dyslipidemia presented to the hospital, he was complaining of hematuria, intermittent periumbilical abdominal pain, and 40-lb weight loss over four months. Initial evaluation showed symptomatic anemia and large blood cells with proteinuria on urine analysis. During his clinical course, the patient developed a new diffuse purpuric rash. Imaging showed systemic involvement with ground-glass opacities, diffuse alveolar hemorrhage, and peripancreatic inflammatory changes, consistent with small-vessel vasculitis. Immunological tests confirmed ANCA-associated vasculitis, and kidney biopsy showed ANCA-mediated pauci-immune glomerulonephritis supported by the salvage technique used by pronase immunofluorescence, which provides evidence against the glomerular disease of the complex immune type in the setting of MPO-ANCA seropositivity. Despite the withdrawal of hydralazine and prompt initiation of immunosuppressive therapy and alternating sessions of plasmapheresis, the patient succumbed to acute massive pulmonary hemorrhage and subsequent demise. We recommend that patients on the common antihypertensive, hydralazine, should be monitored with non-specific inflammatory markers and, if warranted, with qualitative and quantitative assessment tools to measure inflammatory disease activity for possible complications of hydralazine drug-induced vasculitis or hydralazine ANCA-associated vasculitis (HAAV). Furthermore, cumulative dosages may be a predisposing factor for HAAV to present as a pulmonary-renal syndrome, which can be fulminant and fatal, despite aggressive efforts. Therefore, screening, revisiting therapy, early diagnosis, and prompt discontinuation of the drug are imperative.

Looks can be Deceiving: A Challenging Case of Anti-Neutrophil Cytoplasmic Autoantibody Associated Vasculitis

[Anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis] (AAV) is an autoimmune disease characterized by systemic vascular inflammation. We present a case of a 76-year-old man who presented with shortness of breath, fatigue, and weakness. He was eventually diagnosed with hydralazine-induced ANCA-associated renal limited glomerulonephritis. The presentation of this case was unique for a few reasons; the patient showed an initial improvement in kidney function, was non-oliguric, and had no systemic signs of vasculitis. This led to the patient being discharged prematurely with the diagnosis of acute tubular necrosis. We discuss educational features of this case and warn future clinicians about the possibility of waxing and waning renal function in these patients, as well as the importance of having a higher index of suspicion for glomerulonephritis in patients who take hydralazine.

Severe cutaneous presentation of hydralazine-induced ANCA vasculitis without renal or pulmonary involvement, complicated by DIC

Hydralazine is a common arterial vasodilator used in the management of congestive heart failure and hypertension. It can be associated with drug-induced lupus and less commonly antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV). Drug-induced AAV typically has a favourable long-term prognosis. It is not commonly associated with primary skin involvement, as most cases also have notable kidney and lung disease. Cases with isolated skin findings are rare. We present a rare case of a 60-year-old woman on long-term hydralazine who presented with AAV with primary skin and mucosal involvement, in the form of diffuse bullous and ulcerative lesions, which posed a diagnostic challenge. Her hospital course was marked by several complications including disseminated intravascular coagulation. She required intensive therapy with high-dose steroids, plasmapheresis and rituximab. She tolerated immunosuppression well and with multidisciplinary supportive care, she recovered well and was able to be discharged from the hospital.

Muscle biopsy in anti-neutrophil cytoplasmic antibody-associated vasculitis: diagnostic yield depends on anti-neutrophil cytoplasmic antibody type, sex and neutrophil count

OBJECTIVES

This study aimed to examine the sensitivity of muscle biopsy (MB) in ANCA-associated vasculitis (AAV), identify factors predicting MB positivity and assess the prognostic value of a positive MB.

METHODS

We conducted a single-centre retrospective study of AAV with an MB performed at diagnosis. AAV classification [granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA)] followed the European Medicines Agency algorithm. A logistic regression model was used to identify the factors associated with MB positivity. Survival curves were generated using the Kaplan-Meier method.

RESULTS

Among 276 AAV patients (1995-2018), 101 had an MB. Seventy-eight patients were included: 33 with GPA, 25 with MPA and 20 with EGPA. MB samples were positive in 45 cases (58%): 17 GPA, 16 MPA and 12 EGPA. Univariate analysis focussed on GPA and MPA, revealed that the MB yield was higher in females [22/31 (71%) vs 11/27 (41%); P = 0.02] and in anti-MPO patients [25/37 (68%) vs 6/19 (32%) for anti-PR3; P = 0.01]. By multivariate analysis, three factors predicted MB positivity: anti-MPO ANCA [odds ratio (OR) 10.67 (CI 2.09, 81.68)], female sex [OR 5.3 (CI 1.16, 32.35)] and neutrophil count [OR 1.33 (CI 1.07, 1.8)]. MB positivity had no impact on relapse, death or end-stage renal disease-free survival.

CONCLUSIONS

MB is a safe and efficient diagnostic tool for AAV. Predictors of MB yield include ANCA type, sex and neutrophil count. MB cannot substitute for kidney biopsy when indicated, but should be considered in other cases.

Anti-neutrophil cytoplasmic antibody associated glomerulonephritis complicating treatment with hydralazine

Hydralazine, a widely used therapy for hypertension and heart failure, can elicit autoimmune disease, including anti-neutrophil cytoplasmic antibody associated glomerulonephritis (ANCA-GN). We identified 80 cases of ANCA-GN complicating treatment with hydralazine, accounting for 4.3% (80/1858 biopsies) of ANCA-GN diagnosed between 2006 and 2019. Over three-fourths of patients were on hydralazine for at least one year, with mean daily dose of approximately 250 mg/day. ANCA testing revealed p-ANCA/myeloperoxidase-ANCA seropositivity in 98%, including 39% with dual p-ANCA/myeloperoxidase-ANCA and cANCA/anti-protinase 3-ANCA positivity, often accompanied by anti-nuclear antibody (89%), anti-histone antibody (98%), and hypocomplementemia (58%). Kidney biopsy revealed necrotizing and crescentic glomerulonephritis, similar to primary ANCA-GN, but significantly less frequently pauci-immune (77 vs. 100%) and more commonly associated with mesangial hypercellularity (30 vs. 5%), electron dense deposits (62 vs. 20%), and endothelial tubuloreticular inclusions (11 vs. 0%); all significant differences. On follow-up, 42 of 51 patients received induction immunosuppression: 19 reached the combined end-points of kidney failure or death and 32 had mean creatinine of 1.49 mg/dL at last follow-up. Thus, hydralazine-associated ANCA-GN often exhibits overlapping clinical and pathologic features of mild immune complex glomerulonephritis resembling lupus nephritis. With discontinuation of hydralazine and immunosuppression, outcomes are similar to primary ANCA-GN.

Isotretinoin induced small vessel vasculitis: a life-threatening pulmonary-renal syndrome-a case report

Oral isotretinoin is a synthetic analog of vitamin - A, reserved for cases with severe resistant acne. We hereby report a case of drug-induced vasculitis (DV) from isotretinoin exposure leading to life-threatening pulmonary-renal syndrome requiring immunosuppression and plasmapheresis. A previously healthy 21-year-old female receiving oral isotretinoin presented with a 10-day history of worsening myalgias, arthralgias, and abdominal pain. Soon after admission she progressed to severe pulmonary-renal syndrome requiring intubation and renal replacement therapy. Urinalysis revealed >50 dysmorphic RBC with casts and renal ultrasound was unremarkable. Serological testing was only positive for antineutrophil cytoplasmic antibodies (ANCA) at 1:80 with Anti- proteinase 3 (PR3) at 830 AU/mL and Anti-histone Ab at 2.9. As clinical presentation and serology are highly suggestive of ANCA associated DV, plasmapheresis, and rituximab were also initiated along with the continuation of steroids. She clinically improved but remained dialysis dependent and received a live donor renal transplant. The temporal relationship of symptom onset and drug initiation with no other possible identifiable etiologies-DV in our case was attributed to isotretinoin exposure. Though considered safe, oral Isotretinoin in rare instances can cause the life-threatening pulmonary-renal syndrome. Given its widespread use, it is prudent that prescribers should educate patients regarding the possible symptoms of vasculitis and to seek immediate medical attention when warranted. Physicians should also be vigilant of this complication and should act swiftly to avoid uneventful outcomes.

Eosinophilic Granulomatosis With Polyangiitis: Dissecting the Pathophysiology

Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a rare multisystemic disease classified both amongst hypereosinophilic disorders and ANCA-associated vasculitis. Vessel inflammation and eosinophilic proliferation are the hallmarks of the disease and main effectors of organ damage. Two distinct disease phenotypes have classically been described according to ANCA-status: the ANCA-negative subset with eosinophil-driven manifestation and the ANCA-positive one with vasculitic manifestations. An analogous dichotomization has also been backed by histological findings and a distinct genetic background. EGPA is typically consider a Th2-mediated disease and blood and tissue eosinophilia represent the cornerstone of diagnosis. Besides, ANCA are known for inducing endothelial injury and vascular inflammation by activating the circulating neutrophils. Thus, the pathogenesis of EGPA seems to be mediated by two coexisting mechanisms. However, the verbatim application of this strict dualism cannot always be translated into routine clinical practice. In the present review we describe the current knowledge on the eosinophilic and ANCA-mediated aspects of EGPA pathogenesis. Finally, we review the rationale of the currently proposed EGPA dichotomy and future research perspectives.

Natalizumab induced blood eosinophilia: A retrospective pharmacovigilance cohort study and review of the literature

OBJECTIVE

To describe frequency of natalizumab related eosinophilia and clinical symptoms of eosinophilic disease in our monocentric cohort.

METHODS

Comparison of clinical characteristics of 115 natalizumab treated and 116 untreated RRMS patients and review of literature.

RESULTS

38% of natalizumab treated patients had eosinophilia, which occurred significantly more frequently compared to untreated MS patients (3%, p-value<0.001). In symptomatic patients, mean eosinophil counts were significantly higher than in asymptomatic patients and symptoms developed within one year.

DISCUSSION

Eosinophilia is a side effect of natalizumab and mostly asymptomatic. However, few patients develop within one year after start of natalizumab an eosinophilic disease as severe side effect.

The biology, pathogenetic role, clinical implications, and open issues of serum anti-neutrophil cytoplasmic antibodies

Anti-neutrophil cytoplasmic antibodies (ANCA) are a group of autoantibodies, predominantly IgG, involved in the pathogenesis of several autoimmune disorders, detected either through indirect immunofluorescence or enzyme-linked immunosorbent assay. By means of indirect immunofluorescence, the main patterns are C-ANCA (cytoplasmic) and P-ANCA (perinuclear), while proteinase 3 (PR3) and myeloperoxidase (MPO) represent the main autoantigens in granulomatosis with polyangiitis and microscopic polyangiitis, both belonging to the family of ANCA-associated vasculitis (AAV). While several experiments established the pathogenicity of MPO-ANCA, evidence remains elusive for PR3-ANCA and an additional target antigen, i.e. LAMP2, has been postulated with specific clinical relevance. The presence of a subset of AAV without ANCA may be explained by the presence of further target antigens or the presence of molecules in blood which make ANCA undetectable. A rise in ANCA titers is not necessarily predictive of a flare of disease in AAV if not accompanied by clinical manifestations. ANCA may develop through variable mechanisms, such as autoantigen complementarity, apoptosis impairment, neutrophil extracellular traps dysfunction and molecular mimicry. We will provide herein a comprehensive review of the available evidence on the biological mechanisms, pathogenetic role, and clinical implications of ANCA testing and disease management. Further, we will address the remaining open challenges in the field, including the role of ANCA in inflammatory bowel disease and in cocaine-induced vasculitis.

Role of Neutrophils in Systemic Vasculitides

Neutrophils and neutrophil extracellular traps (NETs) contribute to the pathogenesis of many autoimmune diseases, including vasculitis. Though neutrophils, and NETs, can break self-tolerance by being a source of autoantigens for autoantibodies in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, playing a key role in driving the autoimmune response, the role of neutrophils and NETs in large vessel vasculitis, including giant cell arteritis (GCA), is not well understood. In this review, we summarize the current insight into molecular mechanisms contributing to neutrophil-mediated pathology in small and medium vessel vasculitis, as well as provide potential translational perspectives on how neutrophils, and NETs, may partake in large vessel vasculitis, a rare disease entity of unclear pathogenesis.

[Cutaneous vasculitis and vasculopathy : Differential diagnosis in biopsies of the lower extremities]

The skin is one of the most frequently involved organs in primary systemic and secondary vasculitis; moreover, a vasculitis can occur as single organ vasculitis, limited to the skin. For most types of vasculitis, the lower extremities constitute common sites with clinical symptoms of palpable purpura, nodules, and ulcers. In histopathology of cutaneous vasculitis, it is of utmost importance to correctly identify the vessel types involved and to discriminate between vasculitic vessel damage, unspecific reactive vessel changes, vascular occlusive diseases, noninflammatory purpura, or perivascular infiltrates due to other inflammatory skin diseases. Small-vessel vasculitis is the most frequent type of cutaneous vasculitis; during florid phases, a dermal leukocytoclastic vasculitis is found regardless of etiology. Additional extravascular changes may give etiological clues, however, a correlation with the clinical picture, radiology, and serology is essential. The biopsy type and technique need to be adjusted to the suspected diagnosis and site of the vessels involved. Polyarteritis nodosa and nodular vasculitis can be diagnosed only in biopsies with sufficient subcutaneous tissue. Especially in cutaneous ulcers, a lateral rim of vital skin and subcutaneous tissue is indispensable for a correct diagnosis. Large-vessel vasculitis is not found in skin biopsies of the lower extremities.

Environmental risk factors associated with ANCA associated vasculitis: A systematic mapping review

BACKGROUND

Anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) is a rare multi-system autoimmune disease, characterised by a pauci-immune necrotising small-vessel vasculitis, with a relapsing and remitting course. Like many autoimmune diseases, the exact aetiology of AAV, and the factors that influence relapse are unknown. Evidence suggests a complex interaction of polygenic genetic susceptibility, epigenetic influences and environmental triggers. This systematic mapping review focuses on the environmental risk factors associated with AAV. The aim was to identify gaps in the literature, thus informing further research.

METHODS

Articles that examined any environmental risk factor in AAV disease activity (new onset disease or relapse) were included. Studies had to make explicit reference to AAV, which includes the 3 clinico-pathological phenotypes (GPA, MPA and EGPA), rather than isolated ANCA-positivity. All articles identified were English-language, full manuscripts involving adult humans (>16 years). There was no restriction on publication date and all study designs, except single case reports, were included. The systematic search was performed on 9th December 2019, using the following databases: EMBASE, Medline (Ovid), Cochrane Library, CINAHL and Web of Science.

RESULTS

The search yielded a total of 2375 articles. 307 duplicates were removed, resulting in the title and abstract of 2068 articles for screening. Of these, 1809 were excluded. Thus, 259 remained for full-text review, of which 181 were excluded. 78 articles were included in this review. The most notable findings support the role of various pollutants - primarily silica and other environmental antigens released during natural disasters and through farming. Assorted geoepidemiological triggers were also identified including seasonality and latitude-dependent factors such as UV radiation. Finally, infection was tightly associated, but the exact microorganism(s) is not clear - Staphylococcus aureus is the most presently convincing.

CONCLUSION

The precise aetiology of AAV has yet to be elucidated. It is likely that different triggers, and the degree to which they influence disease activity, vary by subgroup (e.g. ANCA subtype, geographic region). There is a need for more interoperable disease registries to facilitate international collaboration and hence large-scale epidemiological studies, with novel analytical techniques.

ANCA-associated vasculitis

The anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are a group of disorders involving severe, systemic, small-vessel vasculitis and are characterized by the development of autoantibodies to the neutrophil proteins leukocyte proteinase 3 (PR3-ANCA) or myeloperoxidase (MPO-ANCA). The three AAV subgroups, namely granulomatosis with polyangiitis (GPA), microscopic polyangiitis and eosinophilic GPA (EGPA), are defined according to clinical features. However, genetic and other clinical findings suggest that these clinical syndromes may be better classified as PR3-positive AAV (PR3-AAV), MPO-positive AAV (MPO-AAV) and, for EGPA, by the presence or absence of ANCA (ANCA⁺ or ANCA^-, respectively). Although any tissue can be involved in AAV, the upper and lower respiratory tract and kidneys are most commonly and severely affected. AAVs have a complex and unique pathogenesis, with evidence for a loss of tolerance to neutrophil proteins, which leads to ANCA-mediated neutrophil activation, recruitment and injury, with effector T cells also involved. Without therapy, prognosis is poor but treatments, typically immunosuppressants, have improved survival, albeit with considerable morbidity from glucocorticoids and other immunosuppressive medications. Current challenges include improving the measures of disease activity and risk of relapse, uncertainty about optimal therapy duration and a need for targeted therapies with fewer adverse effects. Meeting these challenges requires a more detailed knowledge of the fundamental biology of AAV as well as cooperative international research and clinical trials with meaningful input from patients.

Aortic Involvement in Antineutrophil Cytoplasmic Antibodies Vasculitis, a Coincidence or a Real Association?

Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) is a type of small-vessel vasculitis. It is unusual for ANCA to involve aorta. However, multiple cases have been found where ANCA involved large vessels, particularly the aorta. Among vasculitides, aortic vasculitis is a part of Takayasu arteritis (TAK). In this review article, we tried to find the mechanism behind the aortic involvement in AAV. PubMed was used as a primary search engine, and all the available cases of aortic, as well as large-vessel involvement in ANCA-associated vasculitis, were thoroughly reviewed. Very limited data was available that could provide the mechanism behind this involvement. It is observed that ANCA-associated aortitis is more common in immunocompromised people; however, cases in previously healthy individuals have also been found. Pathogenesis of ANCA-related aortitis is different from Takayasu arteritis and is more close to ANCA-associated small vasculitis. ANCA-related aortitis involves the aorta through the same mechanism as it uses to involve small vessels. This rare manifestation of ANCA-associated vasculitis could be life-threatening but has a good prognosis if timely diagnosed and treated. ANCA-associated vasculitis must be considered as a differential diagnosis while treating a case of aortitis. We believe that there is a need to revise the classification of different types of vasculitides, and physicians should be aware of the possible overlap between different forms of vasculitides.

2020 international consensus on ANCA testing beyond systemic vasculitis

This document follows up on a 2017 revised international consensus on anti-neutrophil cytoplasm antibodies (ANCA) testing in granulomatosis with polyangiitis and microscopic polyangiitis and focuses on the clinical and diagnostic value of ANCA detection in patients with connective tissue diseases, idiopathic interstitial pneumonia, autoimmune liver diseases, inflammatory bowel diseases, anti-glomerular basement membrane (GBM) disease, infections, malignancy, and during drug treatment. Current evidence suggests that in certain settings beyond systemic vasculitis, ANCA may have clinical, pathogenic and/or diagnostic relevance. Antigen-specific ANCA targeting proteinase-3 and myeloperoxidase should be tested by solid phase immunoassays in any patient with clinical features suggesting ANCA-associated vasculitis and in all patients with anti-GBM disease, idiopathic interstitial pneumonia, and infective endocarditis associated with nephritis, whereas in patients with other aforementioned disorders routine ANCA testing is not recommended. Among patients with autoimmune liver diseases or inflammatory bowel diseases, ANCA testing may be justified in patients with suspected autoimmune hepatitis type 1 who do not have conventional autoantibodies or in case of diagnostic uncertainty to discriminate ulcerative colitis from Crohn's disease. In these cases, ANCA should be tested by indirect immunofluorescence as the target antigens are not yet well characterized. Many questions concerning the optimal use of ANCA testing in patients without ANCA-associated vasculitis remain to be answered.

Drug-induced cutaneous vasculitis and anticoagulant-related cutaneous adverse reactions: insights in pathogenesis, clinical presentation, and treatment

Drug-induced vasculitis and anticoagulant-related skin reactions are commonly encountered in the inpatient and outpatient settings. The spectrum of clinical presentation is broad and ranges from focal, skin-limited disease, to more extensive cutaneous and soft tissue necrosis, to potentially fatal systemic involvement. The prompt recognition of these adverse events can have a significant impact on patient morbidity and mortality. We highlight the key features of the clinical presentation with an emphasis on primary lesion morphology, distribution, and epidemiology of purpuric drug reactions. The proposed pathophysiology, histologic findings, and therapeutic interventions of these potentially life-threatening diseases are discussed.

Hydralazine-induced antineutrophil cytoplasmic antibody-associated vasculitis with pulmonary-renal syndrome: a case report

Background

Hydralazine is a common vasodilator which has been used for the treatment of hypertension and heart failure. Hydralazine can induce antineutrophil cytoplasmic antibody-associated vasculitis due to its auto-immunogenic capability and one of the very rare presentations is pulmonary–renal syndrome.

Case presentation

We report a case of a 64-year-old African American woman, who presented to our emergency room with shortness of breath, orthopnea, paroxysmal nocturnal dyspnea, leg swelling, fatigue, loss of appetite, cough with clear sputum, and lightheadedness. On admission, she developed acute hypoxic respiratory failure requiring intubation and acute renal failure requiring hemodialysis. A serologic workup was positive for antineutrophil cytoplasmic antibody, antinuclear antibody, anti-histone, anti-cardiolipin IgM, and anti-double-stranded DNA antibodies. A renal biopsy was done due to persistent deterioration in kidney function and demonstrated classic crescentic (pauci-immune) glomerulonephritis. Hydralazine was empirically discontinued early in the admission and she was started on corticosteroids and cyclophosphamide following biopsy results. She was clinically stable but remained dependent on hemodialysis after discharge.

Conclusion

Hydralazine-induced antineutrophil cytoplasmic antibody-associated vasculitis with pulmonary–renal syndrome is a rare occurrence. In the setting of hydralazine use, multiple positive antigens, and multisystem involvement, clinicians should consider this rare condition requiring prompt cessation of offending drug, early evaluation with biopsy, and contemplate empiric immunosuppressive therapy while biopsy confirmation is pending.

ANCA associated vasculitis

Vasculitis is characterized by inflammation of the vascular wall. It reaches vessels of different sizes and locations, conditioning multisystem and complex manifestations that require a holistic approach. Antineutrophil cytoplasmic antibody-associated vasculitis has an annual incidence rate of 20 per million inhabitants. It is the result of the interaction of infectious, genetic and environmental factors and manifest itself with varied and unspecific symptoms, often reaching the general state, respiratory and renal systems. The combination of clinical, laboratory, imaging and fundamentally histological changes allows the diagnosis and classification of the extent / severity of the disease necessary for the decision of the therapeutics to be taken. Glucocorticoids are generally used; with methotrexate being considered when localized disease and cyclophosphamide, rituximab or azathioprine when generalized disease. A systematized approach can increase survival rates from 12% to 70% over a 5-year span.

A Case of Diffuse Alveolar Hemorrhage Associated with High-Titer of MPO-ANCA Demonstrating Cytoplasmic Staining Pattern

Diffuse alveolar hemorrhage (DAH) is a life-threatening complication of ANCA-associated vasculitis (AAV) that requires urgent recognition and treatment. A presumptive diagnosis is often rendered without histopathology if concordant positivity of ANCA by indirect immunofluorescence (IIF) and ELISA assays, i.e., P-ANCA+/myeloperoxidase (MPO) Ab+ or C-ANCA+/proteinase-3 (PR3) Ab+, is documented in the context of pulmonary-renal syndrome or rapidly progressive glomerulonephritis. In this respect, the discordance between IIF and ELISA assays poses a diagnostic challenge in the absence of convincing histopathology and involves the risks of delaying the implementation of timely immunosuppressive therapy. Here, we report a 74-year-old woman who developed DAH and was found to have a high titer of MPO-ANCA exhibiting cytoplasmic staining on IIF, i.e., MPO-C-ANCA. The literature suggests that the availability of distinct epitopes on the MPO molecule dictates the perinuclear versus cytoplasmic staining pattern, which potentially explains the discordance between ELISA and IIF assays. Her DAH was controlled in association with seven sessions of plasmapheresis, methylprednisolone 1 gram daily for 3 days followed by 1 mg/kg/day, and rituximab. This case exemplifies the importance of consideration of pretest probability of suspected diagnosis that would realize a plausible interpretation of seemingly inconsistent serological profile and its effective incorporation into the diagnostic reasoning.

Drug Hypersensitivity Reactions

Drug hypersensitivity reactions (DHRs) may be classified based on timing (immediate vs delayed), mechanisms, and pattern of clinical manifestations. Management may include selection of alternative, non-cross reactive agents, drug allergy testing, graded challenge and/or desensitization. Immediate skin testing only identifies risk for immediate-type allergic DHR and has a negative predictive value for only a limited number of drugs (eg, penicillin). Desensitization induces a temporary state of tolerance that is maintained only so long as the drug is continued. This article discusses special considerations about antibiotics, angiotensin-converting enzyme inhibitors, anesthetic agents, aspirin and nonsteroidal antiinflammatory drugs, radiocontrast media, and chemotherapeutic agents.

Incidentally Diagnosed Alport Syndrome in a Patient with Drug-Induced Vasculitis

A 53-year-old woman is admitted with a serum creatinine of 16 mg/dl. Seven months earlier, she was diagnosed with heart failure and started on several medications, including Hydralazine. Laboratory studies revealed the presence of dual Anti-Neutrophil Cytoplasmic Antibodies (anti-MPO and anti-PR3), anti-nuclear and anti-histone antibodies. The clinical diagnosis was Drug-Induced ANCA Vasculitis (DIAV). Kidney histology, however, did not reveal crescents, but showed characteristic features of Alport's syndrome.

Demographic, Clinical, and Immunologic Correlates among a Cohort of 50 Cocaine Users Demonstrating Antineutrophil Cytoplasmic Antibodies

OBJECTIVE

Cocaine/levamisole-associated autoimmunity syndrome (CLAAS) is a poorly understood form of drug-induced autoimmunity. Our goals were to better characterize the spectrum of clinical and immunologic features of CLAAS, to identify demographic risk factors, and to generate new hypotheses regarding pathogenesis.

METHODS

CLAAS subjects were identified between 2001 and 2015 at the University of Washington Medical Center, Harborview Medical Center, and affiliated clinics in Seattle, Washington, USA. Demographic, clinical, and immunologic variables were collected and correlated using contingency and logistic regression analyses. We used similar analyses to compare CLAAS subjects with all individuals exhibiting antineutrophil cytoplasmic antibodies (ANCA+) or cocaine use (Cocaine+) in an associated deidentified clinical data repository.

RESULTS

We identified 50 CLAAS subjects. Compared to all Cocaine+ individuals (n = 2740), CLAAS subjects were more likely to be female and less likely to self-identify as black/African American. CLAAS subjects showed several ANCA patterns, including anti-MPO (myeloperoxidase)/anti-PR3 (proteinase 3) dual reactivity, a finding that appears to be specific to CLAAS. Hematologic, renal, and skin abnormalities were most frequently reported, including neutropenia and skin purpura. Finally, we observed strong, independent associations between the cytoplasmic ANCA (C-ANCA) pattern and mortality.

CONCLUSION

We identify sex and race as important risk modifiers in the developing CLAAS among cocaine users. The development of C-ANCA was associated with increased mortality. Moreover, we confirm the enriched presence of anti-MPO/anti-PR3 dual reactivity in CLAAS, further supporting the diagnostic utility of this feature.

Pulmonary-renal syndrome: diagnostic challenge

Vasculitis presents several diagnostic challenges. Herein, we present a clinical case of a 71- year old woman, observed in our emergency department due to asthenia, vomiting and persistent cough. The patient had a history of progressive renal failure and anaemia over the last years. On physical examinations, fine pulmonary crackles were detected and laboratory test showed haemoglobin 69 g/L, creatinine 4 mg/dL, potassium 6.3 mmol/L, positive antineutrophil cytoplasm antibody (ANCA), with proteins and dimorphic erythrocytes in the urinary sediment. CT analysis of the thorax revealed patchy ground glass haziness, likely due to diffuse alveolar haemorrhage. Pulmonary-renal syndrome was assumed, and induction therapy was initiated. She was discharged after 33 days of hospitalisation. On the following months, ANCA titres remained undetectable, but minor recovery of renal function was observed, requiring haemodialysis. Indeed, the use of aggressive induction therapy at early stage dramatically improve prognosis, maintenance of disease remission may be difficult, as relapse is frequent.

"NETtling" the host: Breaking of tolerance in chronic inflammation and chronic infection

How and why we break tolerance to self-proteins still remains a largely unanswered question. Neutrophils have been identified as a rich source of autoantigens in a wide array of autoimmune diseases that arise as a consequence of different environmental and genetic factors, e.g. rheumatoid arthritis (RA), lupus, vasculitis, cystic fibrosis (CF) etc. Specifically, neutrophil extracellular trap (NET) formation has been identified as a link between innate and adaptive immune responses in autoimmunity. Autoantigens including neutrophil granular proteins (targeted by anti-neutrophil cytoplasmic antibodies, ANCA) as well as post-translationally modified proteins, i.e. citrullinated and carbamylated proteins targeted by anti-citrullinated protein antibodies (ACPA) and anti-carbamylated protein antibodies (ACarPA), respectively, localize to the NETs. Moreover, NETs provide stimuli to dendritic cells that potentiate adaptive autoimmune responses. However, while NETs promote inflammation and appear to induce humoral autoreactivity across autoimmune diseases, the antigen specificity of autoantibodies found in these disorders is striking. These unique autoantigen signatures suggest that not all NETs are created equal and that the environment in which NETs arise shapes their disease-specific character. In this review article, we discuss the effects of different stimuli on the mechanism of NET formation as well as how they contribute to antigen specificity in the breaking of immune tolerance. Specifically, we compare and contrast the autoreactive nature of NETs in two settings of chronic airway inflammation: one triggered by smoking, a recognized environmental NET stimulus in RA patients, and one mediated by Pseudomonas aeruginosa, the most prevalent lung pathogen in CF patients. Finally, we draw attention to novel findings that, together with the specific environmental/chemical stimuli, should be taken into account when investigating how and why antigen specificity arises in the context of NET formation.