Genetic insights into the mechanisms of proliferative glomerulonephritis.

Glomerular visceral epithelial cells (i.e., podocytes) are an essential component of the tripartite glomerular filtration barrier. Healthy podocytes are terminally differentiated cells with limited replicative capacity; however, inappropriate cell cycle reentry can be induced in podocytes by various injurious stimuli. In this issue of the JCI, Yamaguchi et al. report on a somatic mosaic gain-of-function mutation in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic α subunit (p110α, encoded by PIK3CA). The study reveals that activating mutations of p110α can drive podocyte proliferation in PIK3CA-related overgrowth syndrome (PROS). They also showed that selective, small-molecule inhibitors of p110 may be useful for the treatment of proliferative glomerulonephritis.

Histopathologic Characteristics of Childhood Nephrotic Syndrome in a Tertiary Health Facility in Nigeria.

BACKGROUND: Globally, the predominant histopathologic characteristic of childhood nephrotic syndrome has been minimal change nephropathy (MCN). However, some studies from Africa and Nigeria have revealed otherwise. It is imperative that this pattern is re-examined from time to time given changing disease and environmental dynamics from place to place. OBJECTIVE: This study aimed to determine the histopathological characteristics of childhood nephrotic syndrome in Ilorin, northcentral Nigeria. METHODS: A prospective study of all new patients aged 2-14 years who presented with clinical features of nephrotic syndrome between January 2010 to December 2023 at the University of Ilorin Teaching Hospital, Ilorin was carried out. All eligible patients underwent renal biopsy. RESULTS: A total of 47 children with nephrotic syndrome were biopsied comprising of 21 males and 26 females making an M: F ratio of 1:1.2. The age range of subjects was 2-14 years with a mean of 7.8 ±3.6 years. The most common histological type of nephrotic syndrome was minimal change nephrotic syndrome (MCNS) which occurred in 35(74.5%) children followed by membranoproliferative glomerulonephritis (MPGN) in 5(10.6%) and focal segmental glomerulosclerosis (FSGS) in 2(4.3%). Of the 35 MCNS patients, 31(88.6%) were steroid sensitive while 4(11.4%) were steroid resistant. CONCLUSION: The predominant histopathological characteristic of childhood nephrotic syndrome was minimal change nephrotic syndrome, which was mostly steroid-sensitive.

CONTEXTE: Au niveau mondial, la principale caractéristique histopathologique du syndrome néphrotique de l'enfant a été la néphropathie à lésions minimales (NLM). Cependant, certaines études en Afrique et au Nigeria ont montré des résultats différents. Il est essentiel de réévaluer ce modèle régulièrement en raison de l'évolution des maladies et de l'environnement d'un endroit à l'autre. OBJECTIF: Cette étude visait à déterminer les caractéristiques histopathologiques du syndrome néphrotique de l'enfant à Ilorin, dans le nord-centre du Nigeria. MÉTHODES: Une étude prospective de tous les nouveaux patients âgés de 2 à 14 ans présentant des signes cliniques de syndrome néphrotique entre janvier 2010 et décembre 2023 à l'hôpital universitaire d'Ilorin, à Ilorin, a été réalisée. Tous les patients éligibles ont subi une biopsie rénale. RÉSULTATS: Au total, 47 enfants atteints du syndrome néphrotique ont été biopsiés, dont 21 garçons et 26 filles, soit un ratio H/F de 1/1,2. La tranche d'âge des sujets était de 2 à 14 ans avec une moyenne de 7,8 ± 3,6 ans. Le type histologique le plus fréquent du syndrome néphrotique était la néphropathie à lésions minimales (NLM), obser vée chez 35 (74,5 %) enfants, suivie de la glomérulonéphrite membranoproliférative (GMPN) chez 5 (10,6 %) et du sclérose segmentaire et focale (SSF) chez 2 (4,3 %). Parmi les 35 patients atteints de NLM, 31 (88,6 %) étaient cortico-sensibles et 4 (11,4 %) cortico-résistants. CONCLUSION: La principale caractéristique histopathologique du syndrome néphrotique de l'enfant était la néphropathie à lésions minimales, qui était principalement cortico-sensible. MOTS-CLÉS: Syndrome néphrotique, Enfant, Histopathologie, Nigeria.

Membranoproliferative Glomerulonephritis Pattern of Injury.

Membranoproliferative glomerulonephritis (MPGN) is no longer a disease but a pattern of injury in various diseases. Characterized by electron-dense deposits, mesangial proliferation, and duplication of the glomerular basement membrane, MPGN was previously classified by findings seen by electron microscopy. However, recognizing complement dysfunction in relation to cases with the MPGN pattern of injury substantially changed our view of its pathogenesis. A new classification, including immune complex-mediated and complement-mediated MPGN, has become preferable and has been adopted by international guidelines. Despite these advancements, accurate diagnosis of MPGN remains a clinical challenge, given the pathological and clinical similarities between immune complex-mediated and complement-mediated MPGN. Additional testing, such as molecular and genetic testing, is often necessary. Here, we will summarize our current understanding of the MPGN pattern of injury from a pathology perspective as an introductory article in the following chapters.

Association Between Membranoproliferative Glomerulonephritis and Colorectal Cancer - A Case Report.

Membranoproliferative glomerulonephritis (MPGN) is a rare glomerular disease characterized by mesangial hypercellularity and thickening of the glomerular basement membrane (GBM). MPGN can be idiopathic or associated with malignancy, systemic immune complex disorders and chronic infections. It has rarely been associated with solid organ tumors, such as lung, gastric, breast or prostate cancer. We report a patient with MPGN and coexisting colorectal carcinoma. A 48-year-old man presented with anemia, loss of weight, hypertension, and nephrotic syndrome. The renal biopsy findings were compatible with type 1 MPGN. The antineutrophilic cytoplasmic antibodies, antinuclear antibodies, anti-GBM, serologic markers of hepatitis B and hepatitis C and tumor markers were negative. After ruling out the secondary causes of MPGN, the patient was treated with pulse doses of methylprednisolone and a single dose of cyclophosphamide. However, due to the worsening anemia and rectal bleeding, a colonoscopy was performed, which established a diagnosis of adenocarcinoma of the descending colon. The patient was treated with left hemicolectomy and oral corticosteroids. Within a year after the cancer treatment, the patient experienced a complete resolution of the proteinuria and improvement of the kidney function. Although rare, MPGN can be associated with hematologic malignancies and solid organ tumors. The most common causes of secondary MPGN should be ruled out before starting specific treatment. In our patient, cancer treatment has led to a subsequent remission of the nephrotic syndrome, which indicated that this association was not coincidental but rather causal. In patients with a tumor and concomitant glomerulopathy which is suspected to be paraneoplastic in etiology, the treatment of the underlying malignancy should be prioritized.

Clinical characteristics and outcomes of immune-complex membranoproliferative glomerulonephritis and C3 glomerulopathy in Japanese children.

BACKGROUND: Membranoproliferative glomerulonephritis (MPGN) can be divided into immune-complex MPGN (IC-MPGN) and C3 glomerulopathy (C3G), which includes dense deposit disease (DDD) and C3 glomerulonephritis (C3GN). These conditions result from abnormalities in different complement pathways and may lead to different prognoses. However, there are limited studies describing the respective clinical courses. METHODS: In this study, Japanese pediatric patients diagnosed with MPGN based on kidney biopsies conducted between February 2002 and December 2022 were reclassified as having IC-MPGN or C3G (DDD or C3GN). We retrospectively analyzed the clinical characteristics and outcomes of these patients. RESULTS: Out of 25 patients with MPGN, three (12.0%) were diagnosed with DDD, 20 (80.0%) with C3GN, and two (8.0%) with IC-MPGN. There were 13 (65.0%) patients and one (33.3%) patient in remission after treatment for C3GN and DDD, respectively, and no patients with IC-MPGN achieved remission. The median follow-up period was 5.3 (2.5-8.9) years, and none of the patients in either group progressed to an estimated glomerular filtration rate < 15 ml/min/1.73 m2. Patients with C3GN presenting mild to moderate proteinuria (n = 8) received a renin-angiotensin system inhibitor (RAS-I) alone, and these patients exhibited a significant decrease in the urinary protein creatinine ratio and a notable increase in serum C3 levels at the last follow-up. CONCLUSIONS: Most patients with MPGN were diagnosed with C3GN. The remission rate for C3GN was high, and no patients developed kidney failure during the approximately 5-year follow-up. Additionally, patients with C3GN with mild to moderate proteinuria had good outcomes with RAS-I alone, but continued vigilance is necessary to determine long-term prognosis.

Hydralazine use can be associated with IgM-dominated immune complex-mediated glomerulonephritis.

CONTEXT: IgM-dominant immune complex-mediated glomerulonephritis (IgM-dominant ICMGN) is a rare renal entity, characterized by a membranoproliferative pattern by light microscopy, dominant IgM staining by immunofluorescent staining, and subendothelial deposits by electron microscopy. This study was to investigate if some of IgM-ICMGN were associated with autoimmune disorders induced by hydralazine. DESIGN: Seven IgM-dominant ICMGN cases were identified over 8 years. Their pathologic phenotypes and clinical scenarios were analyzed in detail. RESULTS: Patients' ages ranged from 47 to 87 years old with 5 women and two men. Six of seven patients had drug-induced autoimmune phenomenon (hydralazine-induced positive ANCA and ANA). All of them had renal dysfunction and some proteinuria. Most pathologic features showed a membranoproliferative pattern of glomerulonephritis with dominant IgM deposits at subendothelial spaces. IgM nephropathy (a variant of focal segmental glomerulosclerosis), chronic thrombotic microangiopathy, and cryoglobulinemic glomerulopathy were ruled out in the cases. CONCLUSION: The hydralazine-induced autoimmune phenomenon can be seen in IgM-dominant ICMGN, which should be classified as a subtype of membranoproliferative glomerulonephritis.

Seeing through the density of dense deposit disease.

Little is known about what constitutes the dense deposits of dense deposit disease (DDD), apart from components of the complement pathway. This study presents the novel finding that large accumulations of apolipoprotein E are present in the deposits of DDD, as revealed by mass spectroscopy and confirmed by both confocal microscopy and immunohistochemistry. The findings suggest a new modality for diagnosis of DDD and introduce potential new mechanisms for understanding DDD pathophysiology.

Apolipoprotein E is enriched in dense deposits and is a marker for dense deposit disease in C3 glomerulopathy.

C3 glomerulopathy (C3G) is a rare disease resulting from dysregulation of the alternative pathway of complement. C3G includes C3 glomerulonephritis (C3GN) and dense deposit disease (DDD), both of which are characterized by bright glomerular C3 staining on immunofluorescence studies. However, on electron microscopy (EM), DDD is characterized by dense osmiophilic mesangial and intramembranous deposits along the glomerular basement membranes (GBM), while the deposits of C3GN are not dense. Why the deposits appear dense in DDD and not in C3GN is not known. We performed laser microdissection (LCM) of glomeruli followed by mass spectrometry (MS) in 12 cases each of DDD, C3GN, and pretransplant kidney control biopsies. LCM/MS showed marked accumulation of complement proteins C3, C5, C6, C7, C8, C9 and complement regulating proteins CFHR5, CFHR1, and CFH in C3GN and DDD compared to controls. C3, CFH and CFHR proteins were comparable in C3GN and DDD. Yet, there were significant differences. First, there was a six-to-nine-fold increase of C5-9 in DDD compared to C3GN. Secondly, an unexpected finding was a nine-fold increase in apolipoprotein E (ApoE) in DDD compared to C3GN. Most importantly, immunohistochemical and confocal staining for ApoE mirrored the dense deposit staining in the GBM in DDD but not in C3GN or control cases. Validation studies using 31 C3G cases confirmed the diagnosis of C3GN and DDD in 80.6 % based on ApoE staining. Overall, there is a higher burden of terminal complement pathway proteins in DDD compared to C3GN. Thus, our study shows that dense deposits in DDD are enriched with ApoE compared to C3GN and control cases. Hence, ApoE staining may be used as an adjunct to EM for the diagnosis of DDD and might be valuable when EM is not available.

Recurrent C3 glomerulopathy after kidney transplantation.

The complement system is part of innate immunity and is pivotal in protecting the body against pathogens and maintaining host homeostasis. Activation of the complement system is triggered through multiple pathways, including antibody deposition, a mannan-binding lectin, or activated complement deposition. C3 glomerulopathy (C3G) is a rare glomerular disease driven by complement dysregulation with high post-transplantation recurrence rates. Its treatment is mainly based on immunosuppressive therapies, specifically mycophenolate mofetil and glucocorticoids. Recent years have seen significant progress in understanding complement biology and its role in C3G pathophysiology. New complement-tergeting treatments have been developed and initial trials have shown promising results. However, challenges persist in C3G, with recurrent post-transplantation cases leading to suboptimal outcomes. This review discusses the pathophysiology and management of C3G, with a focus on its recurrence after kidney transplantation.

The Outcome of Pauci-immune Crescentic Glomerulonephritis and Its Prognostic Factors; A single Center Case Series.

INTRODUCTION: Pauci-immune crescentic glomerulonephritis (GN) is the most common cause of rapidly progressive GN in adults. The aim of this study was to determine the outcome of patients with pauci-immune crescentic GN and risk factors of the development of end-stage kidney disease (ESKD) in these patients. METHODS: This case series study was carried on 120 patients with pauci-immune crescentic GN biopsied in our center betwen 1998 and 2016. Inclusion criteria were age > 16 years, at least one crescentic glomerulus, maximally 1+ deposition of immunoglobulins and complement components at fluorescent microscopy, and at least 6 months follow-up. The main outcomes were ESKD and death. RESULTS: The study population included 120 patients with pauciimmune crescentic GN (mean age was 47 ± 17 years and 49.1% male). There was no significant difference in outcome between patients with diffuse or focal crescentic GN. Seventy-two patients (60%) developed ESKD and 31 patients (25.8%) died. The need for dialysis at admission, lower baseline hemoglobin and GFR and GFR at four months and high percentage of glomerulosclerosis and interstitial fibrosis had a significant relationship with low kidney survival (P < .05). The rate of ESKD was higher in patients who did not receive cyclophosphamide therapy, due to focal crescentic GN or high chronicity, compared to patients who received it (70.7 vs. 28.5%, P < .001). CONCLUSION: In our study, a high percentage of patients with pauciimmune crescentic GN developed ESKD. Low first GFR and high chronicity in biopsy were associated with lower kidney survival. Failure to administer cyclophosphamide in seemingly limited or advanced cases, together with late referral may have led to poor prognosis.  DOI: 10.52547/ijkd.7545.

Farmacocinética de eculizumab en pacientes adultos y pediátricos con síndrome hemolítico urémico atípico y glomerulopatía C3 / Pharmacokinetics of eculizumab in adult and pediatric patients with atypical hemolytic uremic syndrome and C3 glomerulopathy

Objetivo analizar y describir las concentraciones de eculizumab y el bloqueo del complemento en los pacientes con síndrome hemolítico urémico atípico (SHUa) y glomerulopatía C3, y definir un margen terapéutico donde se alcance una alta probabilidad de conseguir eficacia terapéutica. Métodos estudio observacional, ambispectivo y multicéntrico que incluyó pacientes adultos y pediátricos diagnosticados de SHUa y glomerulopatía C3 desde septiembre de 2020 hasta octubre de 2022 en 5 hospitales de España. Eculizumab se administró a las dosis recomendadas por la ficha técnica. Se determinaron las concentraciones pre y posdosis de eculizumab, así como del bloqueo de la vía clásica del complemento (CH50). Se recogieron variables sociodemográficas, analíticas y clínicas, y se calcularon los parámetros farmacocinéticos. Para establecer el punto de corte de las concentraciones de eculizumab que predecían el bloqueo del complemento se realizó un análisis de curvas ROC (Receiver Operating Characteristic). Se utilizó el test de Kruskal-Wallis para contrastar las diferencias en distintos parámetros según las concentraciones de eculizumab. Resultados se incluyeron 25 pacientes, 19 adultos (76,0%) y 6 pediátricos (24,0%), con edades medianas de 43,4 (RIC 35,7-48,8) y 10,1 (RIC 9,6-11,3) años, respectivamente. De ellos, 22 (88,0%) pacientes fueron diagnosticados con SHUa y 3 (12,0%) con glomerulopatía C3. Se determinaron un total de 111 concentraciones de eculizumab. Las concentraciones predosis y posdosis medias detectadas durante la fase de mantenimiento fueron 243,8 (SD 240,6) μg/ml y 747,4 (SD 444,3) μg/ml, respectivamente (AU)

Objective The objective of the study was to analyze and describe the concentrations of eculizumab and the complement blockade in patients with atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy, and to define a therapeutic margin where there is a high probability of achieving therapeutic efficacy. Methods Observational, ambispective and multicenter study that included adult and pediatric patients diagnosed with aHUS and C3 glomerulopathy from September 2020 to October 2022 in five hospitals in Spain. Eculizumab was administered at the doses recommended by the data sheet according to the European Medicines Agency (EMA). Pre-dose and post-dose concentrations of eculizumab were determined, as well as blockade of the classical complement pathway (CH50). Sociodemographic and clinical data were collected, and pharmacokinetic parameters were calculated. To establish the cut-off point for eculizumab concentrations that predicted complement blockade, Receiver Operating Characteristic (ROC) curve analysis was performed. Lastly, the Kruskal-Wallis test was used to contrast the differences in different parameters according to eculizumab concentrations. Results Twenty-five patients were included, 19 adults (76.0%) and 6 pediatrics (24.0%), with median ages of 43.4 (IQR 35.7-48.8) and 10.1 (IQR 9.6-11.3) years, respectively. Of these, 22 (88.0%) patients were diagnosed with aHUS and 3 (12.0%) with C3 glomerulopathy. A total of 111 eculizumab concentrations were determined (AU)

Comparison of Clinico-pathologic features and outcomes of ANCA negative and ANCA positive pauci immune crescentic glomerulonephritis: A single centre study.

Introduction: Pauci-immune crescentic glomerulonephritis (PICN) is an important cause of rapidly progressive renal failure. 10-40% of PICN cases have ANCA (antineutrophil cytoplasmic antibody) negative serology. The present study compared clinico-pathologic features, Brix's renal risk score, Berden's histopathological classes and differences in outcome between ANCAnegative vs ANCA positive PICN patients. Materials and Methods: Sixty-one patients of biopsy-proven PICN were studied. Biochemical findings and ANCA serology were recorded. Renal biopsy slides were reviewed along with direct immunofluorescence. Clinical and histological features were compared between ANCA negative and positive PICN using the Man Whitney U test and Chi-square test. Patients were compared for distribution in Berden's histological classes and Brix's renal risk categories. Patient and renal survival were compared using Kaplan-Meier survival analysis. Results: ANCA negative PICN patients were younger (44.9 ± 16.5 years vs 53.6 ± 15.1 years, P = 0.049). Nasal (0 vs 18%, P = 0.035) and pulmonary involvement (9% vs 38%, P = 0.014) were lower in ANCA negative group. Both ANCA groups had similar renal biochemical profiles, percentage normal glomeruli, 16.3 ± 18.2 vs 21.7 ± 20.4 and percentage glomeruli with crescents, 64.5 ± 28.1 vs 64.3 ± 27.1. Twenty-seven per cent of ANCA negative cases fell in the sclerotic class in Berden's classification vs just 2.5% in ANCA positive group (p = 0.037) without significant difference in Brix's renal risk categories (p = 0.329). Thirteen per cent of ANCA negative patients achieved complete remission on treatment compared to 33% in ANCA positive patients. Patient survival and overall probability of progressing to ESRD were similar in the two groups. Conclusion: ANCA negative PICN cases present at younger ages. Nasal and pulmonary involvement is uncommon in these patients. Patient survival and progression to ESRD are similar in both ANCA groups.

To interpret and analyze the changing patterns of histology and direct immunofluorescence findings in membranoproliferative glomerulonephritis.

Background: Membranoproliferative glomerulonephritis has in the recent past been regrouped into immune complex-mediated (ICM MPGN) disease (driven by the classical complement pathway) and complement-mediated (C3GN) disease (driven by the alternative complement pathway) based on pathogenetic role of alternative complement pathway and immunofluorescence deposits. The proposed regrouping lent therapeutic and prognostic support in managing the disease of MPGN. Aims and Objectives: The present study is undertaken to study the patterns of MPGN based on histopathological and DIF examination and sub-categorize the cases into mainly complement dominant and immune complex-mediated diseases for better prognostic and therapeutic utility. Materials and Methods: This is a prospective observational study carried out in a tertiary care center over a period of 2 yrs. The clinically suspected cases of MPGN were subjected to histopathologic and direct immunofluorescence examination (DIF), and the findings were interpreted in light of complement-mediated and immune complex-mediated MPGN. Results: Out of 620 renal biopsies, diagnosis of MPGN was confirmed both on histopathology and DIF in 36 cases accounting for 5.8% of all biopsies. Based on DIF findings, the various groups comprised 20 cases (55.6%) of immune complex deposits, 11 (30.5%) of C3 dominant picture, and 5 (13.9%) of Nil immune deposits. On analysis of the patterns on DIF, 16 cases (80%) of C3 + Ig group and 6 (54.5%) of C3GN group showed predominantly MPGN pattern. Crescentic glomerulonephritis, global glomerulosclerosis, and interstitial fibrosis were markedly observed in C3GN group. Conclusion: DIF is of immense prognostic and therapeutic value in managing cases of MPGN.