Estimating the epidemiology of anti-neutrophil cytoplasm antibody-associated renal vasculitis and the role of histologic chronicity in predicting renal outcomes

EULAR recommendations for the management of ANCA-associated vasculitis: 2022 update

BACKGROUND

Since the publication of the EULAR recommendations for the management of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) in 2016, several randomised clinical trials have been published that have the potential to change clinical care and support the need for an update.

METHODS

Using EULAR standardised operating procedures, the EULAR task force undertook a systematic literature review and sought opinion from 20 experts from 16 countries. We modified existing recommendations and created new recommendations.

RESULTS

Four overarching principles and 17 recommendations were formulated. We recommend biopsies and ANCA testing to assist in establishing a diagnosis of AAV. For remission induction in life-threatening or organ-threatening AAV, we recommend a combination of high-dose glucocorticoids (GCs) in combination with either rituximab or cyclophosphamide. We recommend tapering of the GC dose to a target of 5 mg prednisolone equivalent/day within 4-5 months. Avacopan may be considered as part of a strategy to reduce exposure to GC in granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA). Plasma exchange may be considered in patients with rapidly progressive glomerulonephritis. For remission maintenance of GPA/MPA, we recommend rituximab. In patients with relapsing or refractory eosinophilic GPA, we recommend the use of mepolizumab. Azathioprine and methotrexate are alternatives to biologics for remission maintenance in AAV.

CONCLUSIONS

In the light of recent advancements, these recommendations provide updated guidance on AAV management. As substantial data gaps still exist, informed decision-making between physicians and patients remains of key relevance.

Kidney Biopsy Chronicity Grading in Antineutrophil Cytoplasmic Antibody Associated Vasculitis

Background

Kidney biopsy is valuable for prognostic assessment of renal outcomes in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) with glomerulonephritis (AAV-GN) but the impact of chronic changes is not determined.

Methods

We conducted a retrospective cohort study of myeloperoxidase (MPO)- or proteinase 3 (PR3)-ANCA-positive patients with AAV and active renal disease. We applied the Mayo Clinic Chronicity Score (MCCS) and validated and evaluated its implications on outcome prediction in AAV-GN.

Results

We analyzed 329 patients with kidney biopsies available to score. The extent of chronicity was graded by MCCS as minimal [102 (31.0%)], mild [106 (32.2%)], moderate [86 (26.1%)] and severe [35 (10.6%)]. The MCCS grades correlated with the degree of renal function impairment at presentation [mean estimated glomerular filtration rate (eGFR) 48.3 versus 29.2 versus 23.7 versus 18.5 mL/min/1.73 m², respectively; P < 0.0001]. Higher degrees of the individual components of the MCCS (glomerulosclerosis, interstitial fibrosis, tubular atrophy and arteriosclerosis) were associated with lower median eGFR (P < 0.0001) and decreased event-free [kidney failure (KF) and death] survival (P = 0.002, P < 0.0001, P < 0.0001 and P = 0.017, respectively). Patients with lower MCCS grades recovered renal function more frequently (P < 0.0001). Increasing MCCS grades were associated with decreased renal recovery (P = 0.001), more frequent events and shorter time to KF (P < 0.0001), KF and death (P < 0.0001) and death (P = 0.042), independent of the remission induction treatment used (cyclophosphamide or rituximab). The MCCS stratified renal outcomes for each MCCS grade and can be used in clinical practice as a cutoff for KF prediction (MCCS ≥4).

Conclusions

Chronic changes on kidney histology independently predict renal function, outcomes and response to treatment in AAV-GN.

Systematic Histological Scoring Reveals More Prominent Interstitial Inflammation in Myeloperoxidase-ANCA Compared to Proteinase 3-ANCA Glomerulonephritis

Background: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic vasculitis, most frequently presenting as microscopic polyangiitis (MPA) or granulomatosis with polyangiitis (GPA). Kidney involvement is a common and severe complication of ANCA AAV which is observed in a considerable subset of patients, mainly affecting glomeruli. However, tubulointerstitial lesions have also been described in ANCA glomerulonephritis (GN). Therefore, we aim to describe active and chronic tubulointerstitial lesions in ANCA GN subtypes by systematic scoring analogous to the Banff scoring system while also utilizing clinical and laboratory findings. Methods: A total of 49 kidney biopsies with ANCA GN were retrospectively included in a single-center cohort study between 2015–2020. Results: We report that MPO-ANCA GN is associated with more severe deterioration of kidney function independent of systemic markers of AAV disease activity, and is also associated with increased proteinuria in MPO-ANCA GN and a decreased fraction of normal glomeruli. Finally, MPO-ANCA GN showed distinct, active, and chronic tubulointerstitial lesions. Conclusion: New insights into the pathophysiology of both entities, as well as differences in the clinical presentation of MPO- versus PR3-ANCA GN, could potentially pave the way for more precise treatment regimens. Therefore, it is important to understand the differences in histopathological presentation, especially in yet underestimated active tubulointerstitial lesions of ANCA GN subtypes. This research could further improve our understanding of distinct pathophysiological mechanisms.

Immunopathogenesis of ANCA-Associated Vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is an autoimmune disorder which affects small- and, to a lesser degree, medium-sized vessels. ANCA-associated vasculitis encompasses three disease phenotypes: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). This classification is largely based on clinical presentations and has several limitations. Recent research provided evidence that genetic background, risk of relapse, prognosis, and co-morbidities are more closely related to the ANCA serotype, proteinase 3 (PR3)-ANCA and myeloperoxidase (MPO)-ANCA, compared to the disease phenotypes GPA or MPA. This finding has been extended to the investigation of biomarkers predicting disease activity, which again more closely relate to the ANCA serotype. Discoveries related to the immunopathogenesis translated into clinical practice as targeted therapies are on the rise. This review will summarize the current understanding of the immunopathogenesis of ANCA-associated vasculitis and the interplay between ANCA serotype and proposed disease biomarkers and illustrate how the extending knowledge of the immunopathogenesis will likely translate into development of a personalized medicine approach in the management of ANCA-associated vasculitis.