Histologic and Clinical Factors Associated with Kidney Outcomes in IgA Vasculitis Nephritis.

BACKGROUND: Nephritis is a common manifestation of IgA vasculitis and is morphologically indistinguishable from IgA nephropathy. While MEST-C scores are predictive of kidney outcomes in IgA nephropathy, their value in IgA vasculitis nephritis has not been investigated in large multiethnic cohorts. METHODS: Biopsies from 262 children and 99 adults with IgA vasculitis nephritis ( N =361) from 23 centers in North America, Europe, and Asia were independently scored by three pathologists. MEST-C scores were assessed for correlation with eGFR/proteinuria at biopsy. Because most patients ( N =309, 86%) received immunosuppression, risk factors for outcomes were evaluated in this group using latent class mixed models to identify classes of eGFR trajectories over a median follow-up of 2.7 years (interquartile range, 1.2-5.1). Clinical and histologic parameters associated with each class were determined using logistic regression. RESULTS: M, E, T, and C scores were correlated with either eGFR or proteinuria at biopsy. Two classes were identified by latent class mixed model, one with initial improvement in eGFR followed by a late decline (class 1, N =91) and another with stable eGFR (class 2, N =218). Class 1 was associated with a higher risk of an established kidney outcome (time to ≥30% decline in eGFR or kidney failure; hazard ratio, 5.84; 95% confidence interval, 2.37 to 14.4). Among MEST-C scores, only E1 was associated with class 1 by multivariable analysis. Other factors associated with class 1 were age 18 years and younger, male sex, lower eGFR at biopsy, and extrarenal noncutaneous disease. Fibrous crescents without active changes were associated with class 2. CONCLUSIONS: Kidney outcome in patients with biopsied IgA vasculitis nephritis treated with immunosuppression was determined by clinical risk factors and endocapillary hypercellularity (E1) and fibrous crescents, which are features that are not part of the International Study of Diseases of Children classification.

Dissecting the histological features of lupus nephritis highlights new common patterns of injury in class III/IV.

OBJECTIVE: The International Society of Nephrology/Renal Pathology Society classification is the gold standard for the characterisation of lupus nephritis (LN) on renal biopsy, with therapeutic repercussions. Its recent revision simplified the current class subdivisions, eliminating the S/G forms of class IV, although data on a possible pathogenetic/clinical value of this subdivision are still contradictory. METHODS: 353 renal biopsies from Belimumab International Study in LN were assessed through central pathology review. Univariate logistic models and a decision tree were performed on 314 adequate biopsies to evaluate the impact of histological features on focal/diffuse classes. Removing class I/II (n=6) and 'pure' class V (n=34), principal component analysis (PCA) and heatmap were used to explore similarities among III, IVS and IVG biopsies either incorporating or not the mixed classes (+V, n=274). Finally, a method aimed at partitioning the cases into k clusters based on their similarity (KMeans), was used to study features from the cohort of 'pure' class III/IVS/IVG cases (n=214) to determine alternative subdivisions based on phenotypic data. RESULTS: Segmental endocapillary hypercellularity (EH) was prevalent in class III, global EH, wire loops, hyaline thrombi and double contours were hallmarks of class IVG, with IVS cases showing intermediate characteristics. Heatmap and PCA confirmed the segregation of these features among classes, showing better segregation for focal/diffuse LN as compared with the mixed classes (+V). KMeans revealed the presence of two main clusters, membranoproliferative-like (n=83) or vasculitis-like (n=131). CONCLUSIONS: This study reveals new phenotypic forms of LN surpassing the traditional classes as determined by the current classification. Future validation and confirmation are required to confirm these findings.

[The origins of the Renal Immunopathology Group of the Italian Society of Nephrology].

This article describes the birth and development of the Renal Immunopathology Group of the Italian Society of Nephrology. It collects the stories of nephrologists and pathologists who, since the early Seventies up to the first decade of this century, devoted their professional lives to the study of renal pathology with a strong personal involvement, characterized by enthusiasm, commitment, ability, strong spirit of cooperation, and friendship. All this enabled the Group to: propose the criteria for a standardized histological and immuno-histological examination of renal biopsies and reporting; produce several multicenter studies, whose results were also published in important international journals; to set up a national registry of renal biopsies; to organize a number of courses, some of which were associated with the publication of monographs, on various renal diseases. This article also traces the history of renal pathology in Italy from the second half of the Sixties - when young Italian nephrologists and pathologists from different institutions moved to French laboratories to learn new techniques to apply to renal biopsies - up to the present days. It also shows us how Italian renal pathology has been an essential tool for the development of the nephrological clinical practice and the advancement of scientific research.

Digital pathology for the routine diagnosis of renal diseases: a standard model.

Whole-slide imaging and virtual microscopy are useful tools implemented in the routine pathology workflow in the last 10 years, allowing primary diagnosis or second-opinions (telepathology) and demonstrating a substantial role in multidisciplinary meetings and education. The regulatory approval of this technology led to the progressive digitalization of routine pathological practice. Previous experiences on renal biopsies stressed the need to create integrate networks to share cases for diagnostic and research purposes. In the current paper, we described a virtual lab studying the routine renal biopsies that have been collected from 14 different Italian Nephrology centers between January 2014 and December 2019. For each case, light microscopy (LM) and immunofluorescence (IF) have been processed, analysed and scanned. Additional pictures (eg. electron micrographs) along with the final encrypted report were uploaded on the web-based platform. The number and type of specimens processed for every technique, the provisional and final diagnosis, and the turnaround-time (TAT) have been recorded. Among 826 cases, 4.5% were second opinion biopsies and only 4% were suboptimal/inadequate for the diagnosis. Transmission electron microscopy (TEM) has been performed on 41% of cases, in 22% changing the final diagnosis, in the remaining 78% contributed to the better definition of the disease. For light microscopy and IF the median TAT was of 2 working days, with only 8.6% with a TAT longer than 5 days. For TEM, the average TAT was 26 days (IQR 6-64). In summary, we systematically reviewed the 6-years long nephropathological experience of an Italian renal pathology service, where digital pathology is a definitive standard of care for the routine diagnosis of glomerulonephritides.

Developments in the Histopathological Classification of ANCA-Associated Glomerulonephritis.

BACKGROUND AND OBJECTIVES: The histopathologic classification for ANCA-associated GN distinguishes four classes on the basis of patterns of injury. In the original validation study, these classes were ordered by severity of kidney function loss as follows: focal, crescentic, mixed, and sclerotic. Subsequent validation studies disagreed on outcomes in the crescentic and mixed classes. This study, driven by the original investigators, provides several analyses in order to determine the current position of the histopathologic classification of ANCA-associated GN. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A validation study was performed with newly collected data from 145 patients from ten centers worldwide, including an analysis of interobserver agreement on the histopathologic evaluation of the kidney biopsies. This study also included a meta-analysis on previous validation studies and a validation of the recently proposed ANCA kidney risk score. RESULTS: The validation study showed that kidney failure at 10-year follow-up was significantly different between the histopathologic classes (P<0.001). Kidney failure at 10-year follow-up was 14% in the crescentic class versus 20% in the mixed class (P=0.98). In the meta-analysis, no significant difference in kidney failure was also observed when crescentic class was compared with mixed class (relative risk, 1.15; 95% confidence interval, 0.94 to 1.41). When we applied the ANCA kidney risk score to our cohort, kidney survival at 3 years was 100%, 96%, and 77% in the low-, medium-, and high-risk groups, respectively (P<0.001). These survival percentages are higher compared with the percentages in the original study. CONCLUSIONS: The crescentic and mixed classes seem to have a similar prognosis, also after adjusting for differences in patient populations, treatment, and interobserver agreement. However, at this stage, we are not inclined to merge the crescentic and mixed classes because the reported confidence intervals do not exclude important differences in prognosis and because an important histopathologic distinction would be lost.

Reproducibility of the Oxford classification of immunoglobulin A nephropathy, impact of biopsy scoring on treatment allocation and clinical relevance of disagreements: evidence from the VALidation of IGA study cohort.

BACKGROUND: The VALidation of IGA (VALIGA) study investigated the utility of the Oxford Classification of immunoglobulin A nephropathy (IgAN) in 1147 patients from 13 European countries. Methods. Biopsies were scored by local pathologists followed by central review in Oxford. We had two distinct objectives: to assess how closely pathology findings were associated with the decision to give corticosteroid/immunosuppressive (CS/IS) treatments, and to determine the impact of differences in MEST-C scoring between central and local pathologists on the clinical value of the Oxford Classification. We tested for each lesion the associations between the type of agreement (local and central pathologists scoring absent, local present and central absent, local absent and central present, both scoring present) with the initial clinical assessment, as well as long-term outcomes in those patients who did not receive CS/IS. RESULTS: All glomerular lesions (M, E, C and S) assessed by local pathologists were independently associated with the decision to administer CS/IS therapy, while the severity of tubulointerstitial lesions was not. Reproducibility between local and central pathologists was moderate for S (segmental sclerosis) and T (tubular atrophy/interstitial fibrosis), and poor for M (mesangial hypercellularity), E (endocapillary hypercellularity) and C (crescents). Local pathologists found statistically more of each lesion, except for the S lesion, which was more frequent with central review. Disagreements were more likely to occur when the proportion of glomeruli affected was low. The M lesion, assessed by central pathologists, correlated better with the severity of the disease at presentation and discriminated better with outcomes. In contrast, the E lesion, evaluated by local pathologists, correlated better with the clinical presentation and outcomes when compared with central review. Both C and S lesions, when discordant between local and central pathologists, had a clinical phenotype intermediate to double absent lesions (milder disease) and double present (more severe). CONCLUSION: We conclude that differences in the scoring of MEST-C criteria between local pathologists and a central reviewer have a significant impact on the prognostic value of the Oxford Classification. Since the decision to offer immunosuppressive therapy in this cohort was intimately associated with the MEST-C score, this study indicates a need for a more detailed guidance for pathologists in the scoring of IgAN biopsies.

Revision of the International Society of Nephrology/Renal Pathology Society classification for lupus nephritis: clarification of definitions, and modified National Institutes of Health activity and chronicity indices.

We present a consensus report pertaining to the improved clarity of definitions and classification of glomerular lesions in lupus nephritis that derived from a meeting of 18 members of an international nephropathology working group in Leiden, Netherlands, in 2016. Here we report detailed recommendations on issues for which we can propose adjustments based on existing evidence and current consensus opinion (phase 1). New definitions are provided for mesangial hypercellularity and for cellular, fibrocellular, and fibrous crescents. The term "endocapillary proliferation" is eliminated and the definition of endocapillary hypercellularity considered in some detail. We also eliminate the class IV-S and IV-G subdivisions of class IV lupus nephritis. The active and chronic designations for class III/IV lesions are replaced by a proposal for activity and chronicity indices that should be applied to all classes. In the activity index, we include fibrinoid necrosis as a specific descriptor. We also make recommendations on issues for which there are limited data at present and that can best be addressed in future studies (phase 2). We propose to proceed to these investigations, with clinicopathologic studies and tests of interobserver reproducibility to evaluate the applications of the proposed definitions and to classify lupus nephritis lesions.

Association of kidney fibrosis with urinary peptides: a path towards non-invasive liquid biopsies?

Chronic kidney disease (CKD) is a prevalent cause of morbidity and mortality worldwide. A hallmark of CKD progression is renal fibrosis characterized by excessive accumulation of extracellular matrix (ECM) proteins. In this study, we aimed to investigate the correlation of the urinary proteome classifier CKD273 and individual urinary peptides with the degree of fibrosis. In total, 42 kidney biopsies and urine samples were examined. The percentage of fibrosis per total tissue area was assessed in Masson trichrome stained kidney tissues. The urinary proteome was analysed by capillary electrophoresis coupled to mass spectrometry. CKD273 displayed a significant and positive correlation with the degree of fibrosis (Rho = 0.430, P = 0.0044), while the routinely used parameters (glomerular filtration rate, urine albumin-to-creatinine ratio and urine protein-to-creatinine ratio) did not (Rho = -0.222; -0.137; -0.070 and P = 0.16; 0.39; 0.66, respectively). We identified seven fibrosis-associated peptides displaying a significant and negative correlation with the degree of fibrosis. All peptides were collagen fragments, suggesting that these may be causally related to the observed accumulation of ECM in the kidneys. CKD273 and specific peptides are significantly associated with kidney fibrosis; such an association could not be detected by other biomarkers for CKD. These non-invasive fibrosis-related biomarkers can potentially be implemented in future trials.

Clinicopathological characteristics of typical and atypical anti-glomerular basement membrane nephritis.

Anti-glomerular basement membrane (GBM) antibody disease is a rare pathological condition that mainly involves renal and/or pulmonary parenchyma. It is characterized by the presence of circulating anti-GBM antibodies accompanied by a linear deposition of immunoglobulins (Ig) detected through immunofluorescence (IF) technique and typical signs and symptoms of organ dysfunction, such as rapidly progressive glomerulonephritis (RPGN) and pulmonary hemorrhage (PH). However, recently atypical forms of anti-GBM disease have been described and the presence of overlapping diseases contributed to make its diagnosis challenging. In this review will be discussed the entire spectrum of renal anti-GBM related conditions, focusing the attention on the differences in terms of pathogenesis, diagnosis and therapy of these disparate entities.

Risk factors for progression in children and young adults with IgA nephropathy: an analysis of 261 cases from the VALIGA European cohort.

BACKGROUND: There is a need for early identification of children with immunoglobulin A nephropathy (IgAN) at risk of progression of kidney disease. METHODS: Data on 261 young patients [age <23 years; mean follow-up of 4.9 (range 2.5-8.1) years] enrolled in VALIGA, a study designed to validate the Oxford Classification of IgAN, were assessed. Renal biopsies were scored for the presence of mesangial hypercellularity (M1), endocapillary hypercellularity (E1), segmental glomerulosclerosis (S1), tubular atrophy/interstitial fibrosis (T1-2) (MEST score) and crescents (C1). Progression was assessed as end stage renal disease and/or a 50 % loss of estimated glomerular filtration rate (eGFR) (combined endpoint) as well as the rate of renal function decline (slope of eGFR). Cox regression and tree classification binary models were used and compared. RESULTS: In this cohort of 261 subjects aged <23 years, Cox analysis validated the MEST M, S and T scores for predicting survival to the combined endpoint but failed to prove that these scores had predictive value in the sub-group of 174 children aged <18 years. The regression tree classification indicated that patients with M1 were at risk of developing higher time-averaged proteinuria (p < 0.0001) and the combined endpoint (p < 0.001). An initial proteinuria of ≥0.4 g/day/1.73 m2 and an eGFR of <90 ml/min/1.73 m2 were determined to be risk factors in subjects with M0. Children aged <16 years with M0 and well-preserved eGFR (>90 ml/min/1.73 m2) at presentation had a significantly high probability of proteinuria remission during follow-up and a higher remission rate following treatment with corticosteroid and/or immunosuppressive therapy. CONCLUSION: This new statistical approach has identified clinical and histological risk factors associated with outcome in children and young adults with IgAN.

The putative role of MALDI-MSI in the study of Membranous Nephropathy.

Membranous Nephropathy (MN) is an immunocomplex mediated renal disease that represents one of the most frequent glomerulopathies worldwide. This glomerular disease can manifest as primary (idiopathic) or secondary and this distinction is crucial when choosing the most appropriate course of treatment. In secondary cases, the best strategy involves treating the underlying disease, whereas in primary forms, the identification of confirmatory markers of the idiopathic etiology underlining the process is requested by clinicians. Among those currently reported, the positivity to circulating antigens (PLA2R, IgG4 and THSD7A) was demonstrated in approximately 75% of iMN patients, while approximately 1 in 4 patients with iMN still lack a putative diagnostic marker. Ultimately, the discovery of biomarkers to help further stratify these two different forms of glomerulopathy seems mandatory. Here, MALDI-MSI was applied to FFPE renal biopsies from histologically diagnosed primary and secondary MN patients (n=20) in order to detect alterations in their tissue proteome. MALDI-MSI was able to generate molecular signatures of primary and secondary MN, with one particular signal (m/z 1459), identified as Serine/threonine-protein kinase MRCK gamma, being over-expressed in the glomeruli of primary MN patients with respect to secondary MN. Furthermore, a number of signals that could differentiate the different forms of iMN that were positive to PLA2R or IgG4 were detected, as well as a further set of signals (m/z 1094, 1116, 1381 and 1459) that could distinguish these patients from those who were negative to both. These signals could potentially represent future targets for the further stratification of iMN patients. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann.

ANCA-Associated Glomerulonephritis: Risk Factors for Renal Relapse.

Relapse in ANCA-associated vasculitis (AAV) has been studied previously, but there are few studies on renal relapse in particular. Identifying patients at high risk of renal relapse may aid in optimizing clinical management. We investigated which clinical and histological parameters are risk factors for renal relapse in ANCA-associated glomerulonephritis (AAGN). Patients (n = 174) were newly diagnosed and had mild-moderate or severe renal involvement. Data were derived from two trials of the European Vasculitis Society: MEPEX and CYCAZAREM. The Cox regression model was used to identify parameters increasing the instantaneous risk (= rate) of renal relapse (useful for instant clinical decisions). For identifying predictors of renal relapse during follow-up, we used Fine & Gray's regression model. Competing events were end-stage renal failure and death. The cumulative incidence of renal relapse at 5 years was 9.5% (95% CI: 4.8-14.3%). In the Cox model, sclerotic class AAGN increased the instantaneous risk of renal relapse. In Fine & Gray's model, the absence of interstitial infiltrates at diagnosis was predictive for renal relapse. In this study we used two different models to identify possible relationships between clinical and histopathological parameters at time of diagnosis of AAV with the risk of experiencing renal relapse. Sclerotic class AAGN increased the instantaneous risk of renal relapse. This association is most likely due to the high proportion of sclerosed glomeruli reducing the compensatory capacity. The absence of interstitial infiltrates increased the risk of renal relapse which is a warning sign that patients with a relatively benign onset of disease may also be prone to renal relapse. Renal relapses occurring in patients with sclerotic class AAGN and renal relapses occurring in patients without interstitial infiltrates were mutually exclusive, which may indicate that they are essentially different.

α-1-Antitrypsin detected by MALDI imaging in the study of glomerulonephritis: Its relevance in chronic kidney disease progression.

Idiopathic glomerulonephritis (GN), such as membranous glomerulonephritis, focal segmental glomerulosclerosis (FSGS), and IgA nephropathy (IgAN), represent the most frequent primary glomerular kidney diseases (GKDs) worldwide. Although the renal biopsy currently remains the gold standard for the routine diagnosis of idiopathic GN, the invasiveness and diagnostic difficulty related with this procedure highlight the strong need for new diagnostic and prognostic biomarkers to be translated into less invasive diagnostic tools. MALDI-MS imaging MALDI-MSI was applied to fresh-frozen bioptic renal tissue from patients with a histological diagnosis of FSGS (n = 6), IgAN, (n = 6) and membranous glomerulonephritis (n = 7), and from controls (n = 4) in order to detect specific molecular signatures of primary glomerulonephritis. MALDI-MSI was able to generate molecular signatures capable to distinguish between normal kidney and pathological GN, with specific signals (m/z 4025, 4048, and 4963) representing potential indicators of chronic kidney disease development. Moreover, specific disease-related signatures (m/z 4025 and 4048 for FSGS, m/z 4963 and 5072 for IgAN) were detected. Of these signals, m/z 4048 was identified as α-1-antitrypsin and was shown to be localized to the podocytes within sclerotic glomeruli by immunohistochemistry. α-1-Antitrypsin could be one of the markers of podocyte stress that is correlated with the development of FSGS due to both an excessive loss and a hypertrophy of podocytes.

Tonsillectomy in a European Cohort of 1,147 Patients with IgA Nephropathy.

BACKGROUND: Tonsillectomy has been considered a treatment for IgA nephropathy (IgAN). It is aimed at removing a source of pathogens, reducing mucosa-associated lymphoid tissue and decreasing polymeric IgA synthesis. However, its beneficial effect is still controversial. In Asia, favorable outcomes have been claimed mostly in association with corticosteroids. In Europe, small, single-center uncontrolled studies have failed to show benefits. METHODS: The European validation study of the Oxford classification of IgAN (VALIGA) collected data from 1,147 patients with IgAN over a follow-up of 4.7 years. We investigated the outcome of progression to end-stage renal disease (ESRD) and/or 50% loss of estimated glomerular filtration rate (eGFR) and the annual loss of eGFR in 61 patients who had had tonsillectomy. RESULTS: Using the propensity score, which is a logistic regression model, we paired 41 patients with tonsillectomy and 41 without tonsillectomy with similar risk of progression (gender, age, race, mean blood pressure, proteinuria, eGFR at renal biopsy, previous treatments and Oxford MEST scores). No significant difference was found in the outcome. Moreover, we performed an additional propensity score pairing 17 patients who underwent tonsillectomy after the diagnosis of IgAN and 51 without tonsillectomy with similar risk of progression at renal biopsy and subsequent treatments. No significant difference was found in changes in proteinuria, or in the renal end point of 50% reduction in GFR and/or ESRD, or in the annual loss of eGFR. CONCLUSION: In the large VALIGA cohort of European subjects with IgAN, no significant correlation was found between tonsillectomy and renal function decline.

Tubulointerstitial lesions in lupus nephritis: International multicentre study in a large cohort of patients with repeat biopsy.

BACKGROUND: The glomerulocentric International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification is the gold standard for the evaluation of lupus nephritis, while tubulointerstitial (TIN) parameters are often under-recognized in pathological reports. METHODS: Renal biopsies from 142 patients who underwent repeat biopsy (RB) were evaluated for the following histological parameters: (i) inflammatory interstitial infiltrates; (ii) interstitial fibrosis; (iii) tubulitis; and (iv) tubular atrophy. The inter-relationships between the four TIN variables were explored by multivariate analysis. A linear mixed model was used to investigate the potential impact of TIN variables on eGFR and proteinuria at the two biopsy occasions. RESULTS: The study showed that moderate-severe lesions were not so frequent at the reference biopsy, but more extensively represented upon RB. A strong association was found between the two inflammatory indices and between those related to chronic damage, while the relationship with the ISN/RPS classification was present at RB. If class IV-G was the most related with TIN (especially at RB), the existence of primary TIN in class II patients was also confirmed. Finally, our results support the hypothesis that tubulitis is an independent predictive factor for eGFR. CONCLUSIONS: We recommend that the standard histological evaluation of SLE nephritis also includes TIN features.

The Revisited Classification of GN in SLE at 10 Years: Time to Re-Evaluate Histopathologic Lesions.

Over 10 years have passed since the latest revision of the histopathologic classification of lupus nephritis. This revision was a significant improvement compared with the previous version, mainly because of clearer and more concise definitions and the elimination of mixed subclasses. Despite these improvements, there are still some difficulties in the classification for lupus nephritis, many of which are in the definitions provided. In this review, we focus on the difficulties surrounding the evaluation of classes III and IV lesions, particularly the definitions of endocapillary and extracapillary proliferation, the use of the terms endocapillary proliferation and hypercellularity, the clinical relevance of segmental and global subdivision in class IV, and the value of distinguishing lesions that indicate activity and chronicity. Vascular and tubulointerstitial lesions are also discussed. Furthermore, we give an overview of the history of the classification to provide background on the origin and development of the definitions in lupus nephritis. The issues raised in this review as well as the suggestions for improvements may assist with a revision of the lupus nephritis classification in the near future.