Long-term renal injury in ANCA-associated vasculitis: an analysis of 31 patients with follow-up biopsies

Endotrophin, a collagen type VI-derived matrikine, reflects the degree of renal fibrosis in patients with IgA nephropathy and in patients with ANCA-associated vasculitis

BACKGROUND

Renal fibrosis is the hallmark of chronic kidney disease (CKD) and is characterized by an imbalanced extracellular matrix remodelling. Endotrophin (ETP) is a signalling molecule released from collagen type VI (COL VI). ETP can be measured by the PRO-C6 assay, which quantifies the levels of COL VI formation. ETP levels were previously associated with mortality and disease progression in patients with CKD. We hypothesized that serum and urinary ETP levels correlate with the degree of interstitial fibrosis in kidney biopsies from patients with immunoglobulin A nephropathy (IgAN) and patients with anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV).

METHODS

We examined a cohort of 49 IgAN and 47 AAV patients. A validation cohort of 85 IgAN patients was included. ETP was measured in serum (S-ETP) and urine (U-ETP/Cr) samples, taken on the same day before renal biopsy was performed, using the enzyme-linked immunosorbent assay PRO-C6. The biopsies were evaluated for interstitial fibrosis and tubular atrophy according to the Banff and MEST-C scores.

RESULTS

S-ETP and U-ETP/Cr levels correlated with kidney function, increased CKD severity, correlated with the extent of interstitial fibrosis and gradually increased with increasing degree of interstitial fibrosis and tubular atrophy. ETP outperformed the known fibrosis biomarker Dickkopf-3 for discrimination of patients with high fibrotic burden. The association of S-ETP and U-ETP/Cr with the level of kidney fibrosis was confirmed in the validation cohort.

CONCLUSIONS

We demonstrated that high levels of circulating and excreted ETP are not only indicative of lower kidney function, but also reflect the burden of fibrosis in the kidneys.

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.

Glomerulonephritis in AKI: From Pathogenesis to Therapeutic Intervention

Acute kidney injury (AKI) is increasingly emerging as a global emergency. Sepsis, major surgery, and nephrotoxic drugs are the main causes of AKI in hospitalized patients. However, glomerulonephritis accounts for about 10% of AKI episodes in adults, mainly related to rapidly progressive glomerulonephritis resulting from granulomatous polyangiitis (GPA, Wegener granulomatosis), microscopic polyangiitis (MPA), and anti-glomerular basement membrane (GBM) disease. Also, diffuse proliferative lupus nephritis, immunoglobulin A nephropathy, post-streptococcal glomerulonephritis, mixed cryoglobulinemia, mesangiocapillary glomerulonephritis, membranous nephropathy, hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and scleroderma can induce acute renal failure. Early diagnosis of AKI due to glomerulonephritis is crucial for prompt, effective management to improve short- and long-term outcomes. Kidney biopsy is the gold standard for the diagnosis of glomerular disease, but it is not frequently performed in critically ill patients because of their clinical conditions. In this setting, a growing number of diagnostic assays can support the working hypothesis, including antineutrophil cytoplasmic antibodies (ANCAs), anti-double-stranded DNA antibodies, anti-GBM antibodies, antistreptolysin O and anti-DNase B antibodies, cryoglobulins, antiphospholipid antibodies, and complement levels. Therapeutic strategies in AKI patients with glomerulonephritis include high-dose corticosteroids, cyclophosphamide, and plasma exchange. This article reviews the wide spectrum of glomerulopathies associated with AKI, describing the immunological mechanisms underlying glomerular diseases and presenting an overview of the therapeutic options.

Etiological Spectrum and Clinical Features in 215 Patients of Crescentic Glomerulonephritis: Is it Different in India?

INTRODUCTION

Crescentic glomerulonephritis (CrGN) characterized by the presence of crescents in most (≥50%) glomeruli on renal histology clinically presents as rapidly progressive renal failure. It can occur due to diverse etiologies with varying course and renal outcomes. We studied the prognostic significance of its classification as pauci-immune, anti-GBM, and immune-complex mediated CrGN.

MATERIALS AND METHODS

Renal biopsies diagnosed as CrGN over 9 years were included. Clinical, biochemical, serological, and histological features of various classes of CrGN were correlated with renal outcome.

RESULTS

215 biopsies were diagnosed as CrGN during this period. A majority (63%) were immune-complex mediated while 32% were pauci-immune, followed by anti-GBM disease (5%). 85.5% of pauci-immune CrGN were ANCA associated. The levels of proteinuria and serum creatinine were significantly higher in anti-GBM CrGN as compared to the other two classes. The various histological features including Bowman's capsule rupture, peri-glomerular granulomatous reaction, fibrinoid necrosis, and vasculitis were more common in anti-GBM disease and pauci-immune CrGN. The median renal survival was 6.3, 5.3, 2.1 months in immune-complex mediated, pauci-immune, and anti-GBM CrGN, respectively.

CONCLUSION

Immune-complex mediated is the commonest etiology of CrGN in India. Anti-GBM disease has the worst prognosis followed by pauci-immune and immune-complex mediated CrGN. Raised serum creatinine levels (>5mg%) and the degree of glomerulosclerosis at diagnosis were predictors of poor renal survival. High index of suspicion and prompt diagnosis can improve the outcome in these patients.

Biomarkers in ANCA-Associated Vasculitis: Potential Pitfalls and Future Prospects

Over the past 3 decades, significant advancements in the understanding of the pathophysiology of ANCA-associated vasculitis has led to the development of a multitude of potential candidate biomarkers. Accompanied by the advent of increasingly effective therapeutic strategies, the need for a dependable biomarker to help determine the extent of disease activity and risk of relapse is ever present. Implementation of such a biomarker would enable tailored therapy, optimizing disease control while helping to mitigate unnecessary exposure to therapy and potential treatment-related damage. Although far from perfect, ANCA serology and B-cell population are the two main staple biomarker tools widely used in practice to help supplement clinical assessment. Over recent years, the application and progress of more novel biomarker tools have arisen in both organ-limited and multisystem disease, including genomics, urinary proteins, degradation products of the alternative complement system, cytokines, metabolomics, and biospectroscopy. Validation studies and clinical translation of these tools are required, with serial assessment of disease activity and determination of therapy according to biomarker status correlated with patient outcomes.

[Kidney disease care for the elderly]

In our aging population, kidney disease management needs to take into account the frailty of the elderly. Standardized geriatric assessments can be proposed to help clinicians apprehend this dimension in their daily practice. These tools allow to better identify frail patients and offer them more personalized and harmless treatments. This article aims to focus on the kidney diseases commonly observed in elderly patients and analyze their specific nephrogeriatric care modalities. It should be noticed that all known kidney diseases can be also observed in the elderly, most often with a quite similar clinical presentation. This review is thus focused on the diseases most frequently and most specifically observed in elderly patients (except for monoclonal gammopathy associated nephropathies, out of the scope of this work), as well as the peculiarities of old age nephrological care.

Prognostic Factors in Anti-Neutrophil Cytoplasmic Antibody-Associated Glomerulonephritis with Severe Glomerular Sclerosis: A National Registry-Based Cohort Study

Background

Classification of patients with anti-neutrophil cytoplasmic antibody-associated glomerulonephritis (ANCA-GN) into histological classes is useful for predicting a patient's risk of progression to end-stage renal disease (ESRD). However, even in the worst prognostic group, the 5-year end-stage renal disease-free survival rate is as high as 50%.

Objectives

To investigate those prognostic factors indicative of progression to ESRD in patients with ANCA-GN and sclerosing histology.

Methods

Patients from the Norwegian Kidney Biopsy Registry between 1991 and 2012 who had biopsy verified pauci-immune glomerulonephritis, positive ANCA serology, and sclerosing histology were included. Cases with ESRD during follow-up were identified via linkage with the Norwegian Renal Registry. Potential prognostic factors with relevant cut-offs were compared in patients with and without progression to ESRD during follow-up.

Results

Of 23 included patients, 10 progressed to ESRD. ESRD patients had a lower initial estimated glomerular filtration rate (eGFR; 21 versus 52 ml/min/1.73 m²) and a lower percentage of normal glomeruli (4% versus 15%). Five-year risks of ESRD with eGFR >15 versus ≤15 ml/min/1.73 m² were 77% and 15%, with percentage normal glomeruli >10% versus ≤10%, 83% and 39%.

Conclusions

eGFR and percentage of normal glomeruli are strong risk factors for ESRD in ANCA-GN with sclerosing histology.

Impact of Proteinase 3 versus Myeloperoxidase Positivity on Risk of End-Stage Renal Disease in ANCA-Associated Glomerulonephritis Stratified by Histological Classification: A Population-Based Cohort Study

Background

End-stage renal disease (ESRD) risk in patients with antineutrophil cytoplasmic antibody- (ANCA-) associated glomerulonephritis (ANCA-GN) according to ANCA serotype and stratified by histological classification has not been previously investigated.

Methods

Patients from the Norwegian Kidney Biopsy Registry (NKBR) between 1991 and 2012 who had biopsy-verified pauci-immune glomerulonephritis and positive antineutrophil cytoplasmic antibody serology were included. Cases with ESRD during follow-up were identified in the Norwegian Renal Registry. ESRD-free survival with proteinase 3 (PR3) versus myeloperoxidase- (MPO-) ANCA positivity stratified into 4 histological classes was investigated.

Results

Three hundred fifty-eight patients, of whom 87 progressed to ESRD during follow-up, were included. Patients with PR3- as compared to MPO-ANCA were younger (58 versus 64 years, p = 0.001), had a higher percentage of males (62 versus 41%, p < 0.001), had a lower percentage with a sclerozing glomerulonephritis pattern (4 versus 16%, p < 0.001), and had a significantly higher cumulative ESRD-free survival (90 versus 80%, p = 0.007) at 1-year follow-up. No significant differences in cumulative ESRD-free survival with PR3- as compared to MPO-ANCA were observed by histological stratification.

Conclusion

Advanced glomerular sclerosis is found more frequently in patients with MPO-ANCA, explaining the higher risk of ESRD. ANCA serotypes have no impact on prognosis of patients with similar histological findings.

Patient Outcomes in Renal-Limited Antineutrophil Cytoplasmic Antibody Vasculitis With Inactive Histology

Introduction

Little is known about the anticipated disease course for individuals who present with renal-limited antineutrophil cytoplasmic antibody (ANCA)−associated vasculitis but who lack inflammation on a kidney biopsy. The impact of immunosuppression on renal and overall survival is unknown.

Methods

Patients were recruited from 2005 to 2016 from 8 centers worldwide (N = 16) for this descriptive study. All had positive ANCA, elevated serum creatinine with active urine sediment, histologic evidence of pauci-immune glomerulonephritis without active lesions, and had no evidence of extrarenal vasculitis. We describe the characteristics of this cohort and the differences in the clinical, histologic, and therapeutic parameters of those who developed primary outcomes of end-stage renal disease (ESRD) and vasculitis relapse.

Results

The cohort was 63% Caucasian, and 75% were men, with a median age of 62 years. At entry, the mean ± SD estimated glomerular filtration rate (eGFR) was 24 ± 20 ml/min per 1.73 m², and 5 patients required dialysis. Twelve patients received immunosuppressive therapy, 25% experienced disease relapse, and 38% developed ESRD. Patients who developed ESRD had lower baseline eGFRs (8 ± 5 ml/min per 1.73 m² vs. 35 ± 18 ml/min per 1.73 m²; P = 0.001) and more often required dialysis at presentation (83% vs. 0%; P = 0.001). Patients who relapsed were less likely to receive immunosuppression (25% for the relapsed group vs. 92% for the nonrelapsed group; relative risk: 0.27, risk difference: 67%; P = 0.03).

Conclusion

Among these patients, lower initial eGFR and dialysis dependence at presentation might increase the risk for ESRD. Immunosuppression did not affect renal outcomes in this sample of patients but was associated with a reduced risk for vasculitis relapse. More information is needed on factors that predict treatment response in this high-risk group.

Vasculitis for the internist: focus on ANCA-associated vasculitis

Vasculitides comprise several diseases affecting vessels of different sizes, mainly arteries, but also capillaries and veins. Antineutrophil cytoplasm antibody-associated vasculitides (AAVs) belong to the systemic necrotizing small-vessel vasculitis group that comprises granulomatosis with polyangiitis, microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis. Internists often see AAV patients, and although their outcomes are usually good, the disease can be responsible for morbidity and mortality. Herein, after reviewing the literature, we concentrate on selected aspects important for the internist, including classification, diagnostic dilemmas, treatment novelties, and follow-up.

Histopathological Classification and Renal Outcome in Patients with Antineutrophil Cytoplasmic Antibodies-associated Renal Vasculitis: A Study of 186 Patients and Metaanalysis

Objective.

Renal vasculitis is one of the most common manifestations of antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) and renal histology is a key predictor of the outcome. A new histopathologic classification was proposed and validated, but the results are still debated.

Methods.

We performed a retrospective analysis to validate the histopathologic classification and performed a metaanalysis to evaluate its predictive value. There were 186 patients with ANCA-associated renal vasculitis diagnosed at Ruijin Hospital who were enrolled in the retrospective study. The metaanalysis considered the data for 1601 patients.

Results.

In our retrospective study, patients with focal class had the best renal outcome while patients with mixed class had the worst (p < 0.001). Metaanalysis showed that patients with focal class had better renal outcome than did those with crescentic class [risk ratio (RR) 0.23, 95% CI 0.16–0.34, p < 0.00001], with no evidence of heterogeneity (I2 = 0%, p = 0.96). Patients with crescentic class had better renal outcome than did those with sclerotic class (RR 0.52, 95% CI 0.41–0.64, p < 0.00001), with no evidence of heterogeneity (I2 = 2%, p = 0.43). We did not find statistical significance regarding renal outcome between mixed and crescentic classes (RR 1.14, 95% CI 0.91–1.43, p = 0.27), with no evidence of heterogeneity (I2 = 23%, p = 0.19). The retrospective study showed that lung and upper respiratory tract involvement were the most common extrarenal manifestations.

Conclusion.

We demonstrated the clinical utility of histopathologic classification in determining renal outcome in patients with AAV. Metaanalysis showed that patients with focal class had the best outcome while sclerotic class had the worst.

Twenty-five years of RENHIS: a history of histopathological studies within EUVAS

In the early 1990s, an international working group of experienced renal pathologists, the Renal Histology group, set up a scoring system for biopsies with anti-neutrophil cytoplasmic autoantibody (ANCA)-associated glomerulonephritis. This scoring system subdivided glomerular, interstitial and vascular lesions and served as a tool for the evaluation of all renal biopsies from studies of the European Vasculitis Study Group (EUVAS). Histopathological studies gave new insights into the prediction of renal outcome in patients with ANCA-associated glomerulonephritis. Percentage of normal glomeruli and a selected number of interstitial parameters were reliable predictors of long-term follow-up glomerular filtration rate in all studies. Out of these results, a histopathological classification distinguishing focal, crescentic, mixed and sclerotic classes of ANCA-associated glomerulonephritis was developed. Until today, 13 studies have validated this classification system. Future studies will try to determine if and how renal histology could be helpful in guiding treatment of ANCA-associated glomerulonephritis.

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.

ANCA serotype and histopathological classification for the prediction of renal outcome in ANCA-associated glomerulonephritis

BACKGROUND

The phenotype of renal involvement in anti-neutrophil cytoplasmic antibodies (ANCA) vasculitis has a major influence on survival, and histological subgrouping of diagnostic renal biopsies has been proposed to aid in the prediction of renal outcome. We aimed to validate this histological subgrouping and to investigate the additional value of ANCA serotype in the prediction of renal outcome.

METHODS

Data were retrospectively collected from the time of diagnosis by systematic review of medical records from 136 patients with renal biopsies recruited to cohorts from the UK and Spain, over 15 years. The end point, renal survival, was the composite of end-stage renal disease (ESRD) or death from any cause. The occurrence of ESRD, Stage 4 Kidney Disease Outcomes Quality Initiative-Chronic Kidney Disease, was assessed separately, in order to establish a severity index risk of chronic kidney disease.

RESULTS

Renal survival at 5 years was 96% in the focal, 86% in the crescentic, 81% in the mixed and 61% in the sclerotic subgroups (P = 0.03). Myeloperoxidase (MPO)-ANCA was associated with more severe disease when compared with PR3-ANCA, as demonstrated by a lower frequency of focal and higher frequency of sclerotic subgroups, by more advanced interstitial fibrotic change and by lower glomerular filtration rate at diagnosis and worse renal function at 1 and 2 years.

CONCLUSIONS

We have confirmed the predictive value for renal survival of the ANCA vasculitis histology classification in a multi-centre study. We found a worse renal outcome in patients with tubulointerstitial fibrosis and atrophy. MPO-ANCA positive patients had a worse renal prognosis due to more severe glomerular injury. These results contribute to patient stratification in renal vasculitis for therapeutic, epidemiological and basic research.

Repeat protocol renal biopsy in ANCA-associated renal vasculitis

BACKGROUND

Histopathological lesions in renal biopsy (RB) at presentation of ANCA-associated vasculitis (AAV) have been described in depth but repeat protocolized renal biopsies are seldomly performed in AAV. In this study, we present a group of AAV patients with repeat protocolized biopsies, and we evaluate their clinical significance.

METHODS

A total of 17 consecutive patients diagnosed between 1991 and 1995 with AAV and renal involvement confirmed by biopsy at presentation in a single center underwent a protocol planned rebiopsy in remission after a median of 13 months (range 11-28) from diagnosis. Biopsies were assessed by two independent pathologists, blinded to patient data. Clinical data were collected retrospectively.

RESULTS

Patients were followed-up for a median of 189 months from diagnosis. Renal relapse was observed in eight patients (47.1%), seven patients died, three patients reached end-stage renal failure. There was a significant decrease in the percentage of acute lesions (cellular crescents, fibrinoid necrosis, P < 0.001) and a significant increase in chronic lesions (glomerulosclerosis, interstitial fibrosis, P ≤ 0.01) in the repeat RB compared with the first RB. This resulted in a class change over the biopsies within most patients. The percentage of normal glomeruli in the first biopsy positively correlated with estimated GFR at the end of follow-up (rs = 0.509, P = 0.05).

CONCLUSIONS

This is the first study on protocolized repeat biopsies in AAV, giving insight into disease activity under immunosuppressive treatment. Apparently, many AAV patients have grumbling disease with ongoing activity, eventually leading to an increased amount of chronic lesions.

Validation of the new classification of pauci-immune glomerulonephritis in a United States cohort and its correlation with renal outcome

Background

Renal biopsies provide important diagnostic and prognostic information in ANCA associated glomerulonephritis. A new classification for prognostication of pauci-immune glomerulonephritis (GN) based on four categories (Mixed, Crescentic, Sclerotic and Focal) was proposed by an international working group of renal pathologists (IWGRP). The goal of our study was to apply the proposed classification system to a United States cohort of vasculitis patients and determine the association of IWGRP class with estimated glomerular filtration rate (eGFR) at one year.

Methods

Seventy-six cases of pauci-immune glomerulonephritis diagnosed from 1995 to 2011 from a single center were identified for this retrospective study. Clinical data were collected by abstraction from medical records. Histology was reviewed by a pathologist and classified according to the new classification. MDRD formula was used to calculate eGFR. We correlated IWGRP class to renal function at presentation and at one year. ײ, ANOVA, and linear regression analysis were performed as appropriate.

Results

Renal biopsies were categorized as focal: n = 20, crescentic: n = 18, mixed: n = 27, sclerotic: n = 11. The baseline e-GFR was lowest in the crescentic class and highest in the focal class. In linear regression analysis investigating e-GFR at 1 year; age and baseline e-GFR were independent predictors of e-GFR at 1 year.

Conclusions

The e-GFR at diagnosis and age were predictors of e-GFR at 1 year. Pathologic class at diagnosis may also be a helpful tool in risk stratification at diagnosis.

Treatment of renal manifestations of ANCA-associated vasculitis

CONTEXT

Vasculitis is a clinicopathological entity characterized by inflammation and necrosis of blood vessels.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched.

RESULTS

Two major autoantigens for ANCA are myeloperoxidase (MPO) and proteinase 3 (PR3), which are proteins in the primary granules of neutrophils and in the lysosomes of monocytes. They are expressed in mature neutrophils of patients with ANCA, while absent in healthy subjects.

CONCLUSIONS

The kidney is the most commonly affected vital organ in ANCA-associated vasculitis, and patient outcomes are largely determined by the severity of renal disease at diagnosis and by its response to treatment.

Persistent or New Onset Microscopic Hematuria in Patients with Small Vessel Vasculitis in Remission: Findings on Renal Biopsy

Objective.

Hematuria is considered a sign of active renal disease in patients with small-vessel vasculitis. In patients who are in apparent clinical remission, presence of persistent or new-onset microscopic hematuria may reflect active vasculitis, damage, or other glomerular pathology.

Methods.

We identified 74 patients from the Johns Hopkins Renal Pathology database between 1995 and 2009 with the diagnosis of pauciimmune glomerulonephritis (GN). Among them we identified 9 who were in clinical remission and underwent a renal biopsy for evaluation of persistent or new-onset hematuria.

Results.

Nine patients with small-vessel vasculitis, 8 antineutrophil cytoplasmic antibody (ANCA)-positive and 1 ANCA-negative, underwent a renal biopsy at variable time periods after remission of vasculitis (6 to 164 months) for persistent microscopic hematuria (n = 6) or new-onset microscopic hematuria (n = 3). All patients were in apparent clinical remission at the time of renal biopsy. Of the 3 patients presenting with new-onset hematuria, 2 had crescentic IgA nephropathy and 1 had healed crescentic pauciimmune GN. Of the 6 patients with persistent hematuria, 2 had arteriosclerosis, 2 had focal segmental glomerulosclerosis, and 2 had global and segmental glomerulosclerosis and healed crescentic GN, and none had active vasculitis.

Conclusion.

Microscopic hematuria in patients with renal vasculitis otherwise in remission could represent chronic glomerular injury from prior episode of vasculitis or may represent new glomerular pathology. Renal biopsy should be considered in these patients to guide therapy.

Histopathologic classification of ANCA-associated glomerulonephritis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is the most common cause of rapidly progressive glomerulonephritis worldwide, and the renal biopsy is the gold standard for establishing the diagnosis. Although the prognostic value of the renal biopsy in ANCA-associated glomerulonephritis is widely recognized, there is no consensus regarding its pathologic classification. We present here such a pathologic classification developed by an international working group of renal pathologists. Our classification proposes four general categories of lesions: Focal, crescentic, mixed, and sclerotic. To determine whether these lesions have predictive value for renal outcome, we performed a validation study on 100 biopsies from patients with clinically and histologically confirmed ANCA-associated glomerulonephritis. Two independent pathologists, blinded to patient data, scored all biopsies according to a standardized protocol. Results show that the proposed classification system is of prognostic value for 1- and 5-year renal outcomes. We believe this pathologic classification will aid in the prognostication of patients at the time of diagnosis and facilitate uniform reporting between centers. This classification at some point might also provide means to guide therapy.

Prediction of ESRD in pauci-immune necrotizing glomerulonephritis: quantitative histomorphometric assessment and serum creatinine

Background

Clinical and pathologic features that predict outcome have important potential application in patients with pauci-immune necrotizing glomerulonephritis (usually antineutrophil cytoplasmic antibody–associated vasculitis). This study examines the predictive value of simple quantitative renal histologic measurements in a large cohort with extended follow-up.

Study Design

Cohort study.

Setting & Participants

390 consecutive patients with pauci-immune necrotizing glomerulonephritis at a single hospital (1983-2002); 90 patients underwent repeated kidney biopsy during follow-up.

Predictors

Age and serum creatinine concentration at biopsy, antineutrophil cytoplasmic antibody specificity, percentage of normal glomeruli, percentage of glomeruli with active lesions, and index of chronic damage (quantitative measurement of established cortical damage) in the initial kidney biopsy for all patients. The same factors were assessed in both biopsy specimens for patients undergoing an additional biopsy.

Outcomes & Measurements

End-stage renal disease and patient survival.

Results

Mortality at 1 and 5 years was 23% and 40%, respectively: standardized mortality ratio, 4.74 (95% CI, 3.62-6.32). End-stage renal disease was reached by 14% and 18% at 1 and 5 years, respectively. In multivariable analysis, serum creatinine level at biopsy and percentage of normal glomeruli in the initial biopsy specimen were the best predictors of kidney survival. C Statistics were 0.80 for creatinine level alone and 0.83 for creatinine level with normal glomeruli. In patients undergoing an additional biopsy, rapid progression in the index of chronic damage and serum creatinine level at the second biopsy were associated with kidney survival in multivariable analysis.

Limitations

Retrospective analysis. External validity of the index of chronic damage requires further assessment. Selection bias may influence repeated biopsy analyses.

Conclusions

Serum creatinine level at biopsy best predicts kidney survival in patients with pauci-immune necrotizing glomerulonephritis overall.

Improvement in Relative Survival of Patients with Vasculitis: Study of 101 Cases Compared to the General Population

Immunosuppressive treatment has changed the prognosis of renal vasculitis over time, but improvement in prognosis is difficult to analyze in different historical periods, and can be better demonstrated by comparison with life expectancy of sex- and age-matched people. Long-term survival of 101 patients diagnosed with systemic vasculitis at our center from 1975 to 2002 was retrospectively evaluated in comparison with that of the Region's age- and sex-matched population. Patient and kidney survival significantly increased over time. Multivariate analyses showed that risks of patient and renal death decreased by 10% and 7%, respectively, at each year of follow-up, and increased by 6.3% and 5.2% for each year of age. Relative survival significantly improved over time, approaching that of the general population for cases diagnosed after 1993, mainly in women <60 years (from 0.671 at 5-years in the first period to 0.916 in the last period), while 5-year-relative-survival was still 0.530 and 0.682 in men and women > 60 years, respectively. Poisson-based multinomial analyses confirmed the significant risk of the first periods of diagnosis and of dialysis in worsening of the relative survival of patients compared to that of the general population. Life expectancy in patients with renal vasculitis has improved over time, paralleling a significant increase in steroid pulse/cyclophosphamide association therapy and an earlier diagnosis due to the introduction of the ANCA test. Relative survival has considerably improved, and now approaches that expected in the general population for women, but not for men.

Renal pathology of ANCA-related vasculitis: proposal for standardization of pathological diagnosis in Japan

BACKGROUND

In Japan, systematic evaluation of the histologic parameters of anti-neutrophil cytoplasmic autoantibodies (ANCA)-related vasculitis has been performed according to the Japanese classification by Shigematsu et al. However, this classification is quite different from that of the European Vasculitis Study Group (EUVAS) classification. Therefore, a histological common basis is needed to compare Japanese histological data with the international database.

METHOD

Histological parameters concerning glomerular, tubulointerstitial, and vascular lesions of ANCA-related vasculitis, which are indispensable for clinical management, were elucidated and defined by reviewing, utilizing the merits of, and amending the two scoring systems.

RESULTS AND CONCLUSION

A new comprehensive and standardized scoring system, by which histological quantitative assessment can provide evidence for therapy planning, has been developed for renal biopsy of Japanese ANCA-related vasculitis.

Peritubular endothelium: The Achilles heel of the kidney?

The development of renal ischemia has been postulated to be a main cause of the progressive nature of kidney diseases. In recent years, it has become clear that inappropriate and sustained activation of the endothelium could mediate this phenomenon. Endothelial activation will result in leucostasis and can compromise peritubular flow. The associated sustained redox signaling will also accelerate the development of endothelial senescence. In addition, risk factors for renal disease progression can reduce endothelial repair. In the course of these events, loss of capillary structure and rarefaction develops, which drives the further development of nephron loss. In this mini review, the evidence for this pathophysiological concept as well as the possibility to detect such endothelial activation in the clinical arena is summarized.

Predictors of outcome in idiopathic rapidly progressive glomerulonephritis (IRPGN)

Background

Small vessel vasculitides are known to follow a devastating course towards end-stage renal disease, unless treated with immunosuppressive regiments. We investigated the value of clinical, histological and immunohistochemical parameters as predictors of outcome at diagnosis in patients with pauci immune necrotizing glomerulonephritis.

Methods

In 34 patients the percentage and evolution stage of crescents, the presence of glomerular necrosis, the degree or severity of arteriosclerosis, as well as the extent of tubulointerstitial infiltration, interstial fibrosis and tubular atrophy were assessed. Monoclonal antibodies were used to identify infiltrating macrophages, α-SMA(+) and PCNA(+) cells, the expression of integrins α3β1 and LFA-1β, the adhesion molecule ICAM-1, the growth factor TGF-β1 and the terminal complement component C5b-9.

Results

24 pts (70.6%) showed a complete or partial response to the treatment. The follow-up period was 20 ± 22 months. At multivariate analysis, serum CRP (p = 0.024), the intensity of tubular expression of C5b-9 (p < 0.0001) as well as the extent of glomerular and tubular expression of α3β1 integrin (p = 0.001 and 0.008 respectively) independently predicted the response to treatment. The response rate was better in ANCA(+) pts (p = 0.008). The extent of interstitial infiltrate (p < 0.0001), the severity of tubulointerstitial fibrosis (p < 0.0001) and the severity of tubular TGF-β1 expression (p < 0.0001) were independent predictors of long term outcome of renal function.

Conclusion

Patients with ANCA-associated renal vasculitis seem to respond better to the treatment. Acute phase reactants, such as CRP, implying a more intense parenchymal inflammatory reaction, as well as the intensity of the de novo expression of C5b-9 and the glomerular and tubular expression of α3β1 integrin predict the response to therapy. The severity of TIN lesions and of the tubulo-interstitial TGF-β1 and C5b-9 expression predict an unfavourable outcome.

Clinical and Histologic Determinants of Renal Outcome in ANCA-Associated Vasculitis: A Prospective Analysis of 100 Patients with Severe Renal Involvement

This study aimed to identify clinical and histologic prognostic indicators of renal outcome in patients with ANCA-associated vasculitis and severe renal involvement (serum creatinine >500 micromol/L). One hundred patients who were enrolled in an international, randomized, clinical trial to compare plasma exchange with intravenous methylprednisolone as an additional initial treatment were analyzed prospectively. Diagnostic renal biopsies were performed upon entry into the study. Thirty-nine histologic and nine clinical parameters were determined as candidate predictors of renal outcome. The end points were renal function at the time of diagnosis (GFR0) and 12 mo after diagnosis (GFR12), dialysis at entry and 12 mo after diagnosis, and death. Multivariate analyses were performed. Predictive of GFR0 were age (r = -0.40, P = 0.04), arteriosclerosis (r = -0.53, P = 0.01), segmental crescents (r = 0.35, P = 0.07), and eosinophilic infiltrate (r = -0.41, P = 0.04). Prognostic indicators for GFR12 were age (r = -0.32, P = 0.01), normal glomeruli (r = 0.24, P = 0.04), tubular atrophy (r = -0.28, P = 0.02), intraepithelial infiltrate (r = -0.26, P = 0.03), and GFR0 (r = 0.29, P = 0.01). Fibrous crescents (r = 0.22, P = 0.03) were predictive of dialysis at entry. Normal glomeruli (r = -0.30, P = 0.01) and treatment arm (r = -0.28, P = 0.02) were predictive of dialysis after 12 mo. No parameter predicted death. Both chronic and acute tubulointerstitial lesions predicted GFR12 in severe ANCA-associated glomerulonephritis, whereas plasma exchange was a positive predictor of dialysis independence after 12 mo for the entire patient group. Plasma exchange remained a positive predictor when patients who were dialysis dependent at presentation were analyzed separately (r = -0.36, P = 0.01). Normal glomeruli were a positive predictor of dialysis independence and improved renal function after 12 mo, indicating that the unaffected part of the kidney is vital in determining renal outcome.

Renal involvement in Churg-Strauss syndrome

BACKGROUND

Churg-Strauss syndrome (CSS) is a rare disorder characterized by asthma, eosinophilia, and systemic vasculitis. Renal involvement is not regarded as a prominent feature, and its prevalence and severity vary widely in published reports that usually refer to small series of selected patients.

METHODS

We examined the prevalence, clinicopathologic features, and prognosis of renal disease in 116 patients with CSS.

RESULTS

There were 48 men and 68 women with a mean age of 51.9 years (range, 18 to 86 years). Signs of renal abnormalities were present in 31 patients (26.7%). Rapidly progressive renal insufficiency was documented in 16 patients (13.8%); urinary abnormalities, 14 patients (12.1%); and chronic renal impairment, 1 patient. There were 3 additional cases of obstructive uropathy. Sixteen patients underwent renal biopsy, which showed necrotizing crescentic glomerulonephritis in 11 patients. Other diagnoses were eosinophilic interstitial nephritis, mesangial glomerulonephritis, and focal sclerosis. Antineutrophil cytoplasmic antibody (ANCA) was positive in 21 of 28 patients (75.0%) with nephropathy versus 19 of 74 patients without (25.7%; P < 0.001). In particular, all patients with necrotizing crescentic glomerulonephritis were ANCA positive. After a median follow-up of 4.5 years, 10 patients died (5 patients with nephropathy) and 7 patients developed mild chronic renal insufficiency. Five-year mortality rates were 11.7% (95% confidence interval, 3.9 to 33.3) in patients with nephropathy and 2.7% (95% confidence interval, 0.7 to 10.7) in those without (P = 0.10).

CONCLUSION

Renal abnormalities are present in about one quarter of patients with CSS. The prevailing picture is ANCA-associated necrotizing crescentic glomerulonephritis; however, other forms of nephropathy also may occur. Outcome and long-term follow-up usually are good.

Pathways to nephron loss starting from glomerular diseases-insights from animal models

Studies of glomerular diseases in animal models show that progression toward nephron loss starts with extracapillary lesions, whereby podocytes play the central role. If injuries remain bound within the endocapillary compartment, they will undergo recovery or be repaired by scaring. Degenerative, inflammatory and dysregulative mechanisms leading to nephron loss are distinguished. In addition to several other unique features, the dysregulative mechanisms leading to collapsing glomerulopathy are particular in that glomeruli and tubules are affected in parallel. In contrast, in degenerative and inflammatory diseases, tubular injury is secondary to glomerular lesions. In both of the latter groups of diseases, the progression starts in the glomerulus with the loss of the separation between the tuft and Bowman's capsule by forming cell bridges (parietal cells and/or podocytes) between the glomerular and the parietal basement membranes. Cell bridges develop into tuft adhesions to Bowman's capsule, which initiate the formation of crescents, either by misdirected filtration (proteinaceous crescents) or by epithelial cell proliferation (cellular crescents). Crescents may spread over the entire circumference of the glomerulus and, via the glomerulotubular junction, may extend onto the tubule. Two mechanisms concerning the transfer of a glomerular injury onto the tubulointerstitium are discussed: (1) direct encroachment of extracapillary lesions and (2) protein leakage into tubular urine, resulting in injury to the tubule and the interstitium. There is evidence that direct encroachment is the crucial mechanism. Progression of chronic renal disease is underlain by a vicious cycle which passes on the damage from lost and/or damaged nephrons to so far healthy nephrons. Presently, two mechanisms are discussed: (1) the loss of nephrons leads to compensatory mechanisms in the remaining nephrons (glomerular hypertension, hyperfiltration, hypertrophy) which increase their vulnerability to any further challenge (overload hypothesis); and (2) a proteinuric glomerular disease leads, by some way or another, to tubulointerstitial inflammation and fibrosis, accounting for the further deterioration of renal function (fibrosis hypothesis). So far, no convincing evidence has been published that in primary glomerular diseases fibrosis is harmful to healthy nephrons. The potential of glomerular injuries to regenerate or to be repaired by scaring is limited. The only option for extracapillary injuries with tuft adhesion is repair by formation of a segmental adherent scar (i.e., segmental glomerulosclerosis).

Histological and clinical predictors of early and late renal outcome in ANCA-associated vasculitis

BACKGROUND

Renal involvement remains a major determinant in antineutrophil cytoplasmic autoantibody-associated small vessel vasculitis (AASV). While some patients may develop persistent renal damage, others have a favourable outcome.

METHODS

To identify patients at risk for poor renal outcome, we evaluated 95 renal biopsies (67 initial biopsies and 28 repeat biopsies) of 67 patients with AASV for the presence and extent of active (AI) and chronic (CI) lesions, retrospectively. AI, CI, levels of proteinuria and dose of cyclophosphamide (CYC) were related to renal outcome.

RESULTS

Recovery of renal function in patients initially dialysis dependent was associated with a lower CI compared with patients who remained on dialysis (P<0.001), while AI did not differ significantly. In these patients, age <65 years revealed a positive predictive value of 85% for renal function recovery. Patients initially requiring dialysis exhibited a higher AI and CI compared with those who did not. Renal function in long-term follow-up correlated with CI and the amount of proteinuria. This relationship increased with time, exhibiting at 4 years a correlation coefficient of 0.607 for CI (P<0.01) and of 0.775 for proteinuria (P<0.001). Follow-up biopsies showed a more pronounced CI compared with initial biopsies (P<0.001). None of the investigated initial parameters was predictive for renal relapse. However, there was a relationship between dose and duration of CYC and time to relapse. Compared with the initial biopsy, repeat biopsies of eight patients with a creeping serum creatinine in clinical remission showed a decrease of AI (P<0.001) while CI increased rapidly. These patients also had less initial CYC (NS).

CONCLUSIONS

These data suggest that in AASV, evaluation of renal histopathology is helpful in predicting early and late renal outcome. Chronicity and proteinuria were the best determinants of poor renal prognosis. Activity may regress under therapy, while chronicity may progress despite treatment. The amount of CYC seems to influence the occurrence of early relapses and renal survival.