Remission induced by renal protective therapy in nephrotic syndrome with thin basement membrane in an older patient: a case report.

BACKGROUND: Adult nephrotic syndrome is a well-known kidney disease that causes heavy proteinuria, hypoalbuminemia, hypercholesterolemia, edema, and hypertension. The treatment varies according to its underlying cause but often faces medication resistance or adverse drug effects. CASE PRESENTATION: A Japanese woman in her 80s presented with nephrotic syndrome after a 3 year latent period of urinary protein and occult blood. She did not have any secondary causes of nephrotic syndrome. Renal biopsy revealed thin glomerular basement membrane, partial foot process fusion on electron microscopy with minor glomerular change on light microscopy, and slight coarse immunoglobulin M deposition in the mesangium on immunofluorescence microscopy, which was inconsistent with any other glomerular diseases. Without steroid treatment, she dramatically remitted from proteinuria after the administration of the renal protective agents enalapril, ezetimibe, rosuvastatin, and dapagliflozin. Recurrence after 8 months of follow-up subsided with the administration of additional doses of the agents. CONCLUSIONS: This case illustrated the novel outcomes of combining medical treatment without steroid use for nephrotic syndrome with thin glomerular basement membrane disease. At the time of writing this report, the patient's renal function was stable and she was free of edema, although moderate proteinuria and occult hematuria persisted. The final diagnosis was uncertain because of the lack of genetic investigation; however, the response to the aforementioned medical treatment suggests the effectiveness of the supportive therapy.

Quantitative assessment of glomerular basement membrane collagen IV α chains in paraffin sections from patients with focal segmental glomerulosclerosis and Alport gene variants.

Focal segmental glomerulosclerosis (FSGS) lesions have been linked to variants in COL4A3/A4/A5 genes, which are also mutated in Alport syndrome. Although it could be useful for diagnosis, quantitative evaluation of glomerular basement membrane (GBM) type IV collagen (colIV) networks is not widely used to assess these patients. To do so, we developed immunofluorescence imaging for collagen α5(IV) and α1/2(IV) on kidney paraffin sections with Airyscan confocal microscopy that clearly distinguishes GBM collagen α3α4α5(IV) and α1α1α2(IV) as two distinct layers, allowing quantitative assessment of both colIV networks. The ratios of collagen α5(IV):α1/2(IV) mean fluorescence intensities (α5:α1/2 intensity ratios) and thicknesses (α5:α1/2 thickness ratios) were calculated to represent the levels of collagen α3α4α5(IV) relative to α1α1α2(IV). The α5:α1/2 intensity and thickness ratios were comparable across all 11 control samples, while both ratios were significantly and markedly decreased in all patients with pathogenic or likely pathogenic Alport COL4A variants, supporting validity of this approach. Thus, with further validation of this technique, quantitative measurement of GBM colIV subtype abundance by immunofluorescence, may potentially serve to identify the subgroup of patients with FSGS lesions likely to harbor pathogenic COL4A variants who could benefit from genetic testing.

A case of rapidly progressive glomerulonephritis with double-positive anti-GBM antibody and MPO-ANCA after SARS-CoV-2 vaccination and relapse during 1 year follow-up.

Although mRNA vaccines for COVID-19 are highly beneficial and are recommended for patients with kidney disease, adverse reactions in some patients after vaccination have been problematic. Various vasculitis and renal disorders have been reported after vaccination; however, a causal relationship has not yet been identified. In this report, we describe a case of rapidly progressive glomerulonephritis that developed after SARS-CoV-2 vaccination, in which both anti-glomerular basement membrane (anti-GBM) and myeloperoxidase antineutrophil cytoplasmic antibodies (MPO-ANCA) were present. The patient's renal biopsy showed that of the 48 glomeruli in total, four showed global sclerosis and none showed segmental sclerosis. The biopsy showed 11 cellular glomerular crescents and 5 fibrocellular glomerular crescents. Renal function improved with steroids, rituximab, and plasma exchange. Approximately 9 months later, MPO-ANCA was again elevated, and the pulmonary lesions worsened, again requiring multidisciplinary treatment. This case suggests that caution should be exercised in the development of double-positive disease after vaccination, and that long-term observation may be necessary because of the possibility of relapse.

Development of an automated estimation of foot process width using deep learning in kidney biopsies from patients with Fabry, minimal change, and diabetic kidney diseases.

Podocyte injury plays a key role in pathogenesis of many kidney diseases with increased podocyte foot process width (FPW), an important measure of podocyte injury. Unfortunately, there is no consensus on the best way to estimate FPW and unbiased stereology, the current gold standard, is time consuming and not widely available. To address this, we developed an automated FPW estimation technique using deep learning. A U-Net architecture variant model was trained to semantically segment the podocyte-glomerular basement membrane interface and filtration slits. Additionally, we employed a post-processing computer vision approach to accurately estimate FPW. A custom segmentation utility was also created to manually classify these structures on digital electron microscopy (EM) images and to prepare a training dataset. The model was applied to EM images of kidney biopsies from 56 patients with Fabry disease, 15 with type 2 diabetes, 10 with minimal change disease, and 17 normal individuals. The results were compared with unbiased stereology measurements performed by expert technicians unaware of the clinical information. FPW measured by deep learning and by the expert technicians were highly correlated and not statistically different in any of the studied groups. A Bland-Altman plot confirmed interchangeability of the methods. FPW measurement time per biopsy was substantially reduced by deep learning. Thus, we have developed a novel validated deep learning model for FPW measurement on EM images. The model is accessible through a cloud-based application making calculation of this important biomarker more widely accessible for research and clinical applications.

Successful treatment of coexisting membranous nephropathy and immune thrombocytopenia by eradicating gastric Helicobacter pylori infection: a case report.

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in middle-aged and older adults. MN etiology is mainly primary or idiopathic; however, it may also be secondary to infections, drugs, neoplasms, and autoimmune diseases. We present the case of a 52-year-old Japanese man with coexisting nephrotic MN and immune thrombocytopenic purpura (ITP). Renal biopsy revealed glomerular basement membrane thickening with immunoglobulin (Ig) G and complement component 3 deposition. Glomerular IgG subclass analysis revealed predominant IgG4 deposition with weak IgG1 and IgG2 deposition. IgG3 and phospholipase A2 receptor deposits were negative. Upper endoscopy revealed no ulcers, but histological examination demonstrated Helicobacter pylori infection in the gastric mucosa with elevated IgG antibodies. After gastric Helicobacter pylori eradication, the nephrotic-range proteinuria and thrombocytopenia of the patient were markedly improved without initiation of immunosuppressive treatment. Therefore, clinicians should consider the possibility of Helicobacter pylori infection in patients with coexisting MN and ITP. Further studies are required to demonstrate the associated pathophysiological aspects.

Both sexes develop DKD in the CD1 uninephrectomized streptozotocin mouse model.

Diabetic kidney disease (DKD) is characterized by a progressive increase in albuminuria and typical pathologic features. Recent studies have shown that sex is an important factor to consider in the pathogenesis of DKD. Presently, the hallmarks of this disease have primarily been studied in male rodent models. Here we explored the influence of sex in a murine model of DKD. CD1 mice underwent a right nephrectomy followed by intraperitoneal injection with 200 mg/kg streptozotocin to induce type 1 diabetes. Due to a high mortality rate, females required a reduction in streptozotocin to 150 mg/kg. Mice were followed for 12 weeks. Both sexes developed comparable hyperglycemia, while albuminuria and glomerular volume were increased to a greater degree in females and kidney hypertrophy was only seen in females. Males had a greater increase in blood pressure and glomerular basement membrane thickening, and a greater decrease in endpoint weight. Serum TGFß1 levels were increased only in females. However, both sexes showed a similar increase in induction of kidney fibrosis. T cell and macrophage infiltration were also increased in both sexes. While some differences were observed, overall, both sexes developed clinical and pathologic characteristics of early DKD. Future studies evaluating therapeutic interventions can thus be assessed in both sexes of this DKD model.

Mayo Clinic consensus report on membranous nephropathy: proposal for a novel classification.

Membranous nephropathy (MN) is a pattern of injury caused by autoantibodies binding to specific target antigens, with accumulation of immune complexes along the subepithelial region of glomerular basement membranes. The past 20 years have brought revolutionary advances in the understanding of MN, particularly via the discovery of novel target antigens and their respective autoantibodies. These discoveries have challenged the traditional classification of MN into primary and secondary forms. At least 14 target antigens have been identified, accounting for 80%-90% of cases of MN. Many of the forms of MN associated with these novel MN target antigens have distinctive clinical and pathologic phenotypes. The Mayo Clinic consensus report on MN proposes a 2-step classification of MN. The first step, when possible, is identification of the target antigen, based on a multistep algorithm and using a combination of serology, staining of the kidney biopsy tissue by immunofluorescence or immunohistochemistry, and/or mass spectrometry methodology. The second step is the search for a potential underlying disease or associated condition, which is particularly relevant when knowledge of the target antigen is available to direct it. The meeting acknowledges that the resources and equipment required to perform the proposed testing may not be generally available. However, the meeting consensus was that the time has come to adopt an antigen-based classification of MN because this approach will allow for accurate and specific MN diagnosis, with significant implications for patient management and targeted treatment.

A closer look: ultrastructural evaluation of high-risk progression IgA nephropathy.

This retrospective, cross-sectional study sought to examine the ultrastructural characteristics of glomerular lesions using Transmission Electron Microscopy (TEM) in IgA nephropathy (IgAN) and their relationship with the high risk of progression phenotype defined by KDIGO guideline as proteinuria ≥1 g/24 hours despite 3 months of optimized supportive care. We analyzed 81 IgAN patients (median age 41 years, 67% male, eGFR 43.8 mL/min, proteinuria 1.04 g/day); 42 (52%) of them had high risk of progression. There were no differences in terms of age, sex, comorbidities, eGFR, and hematuria between the two groups. High-risk patients more often had segmental glomerulosclerosis (29% vs 8%, p 0.01) in optical microscopy, while in TEM had more frequent podocyte hypertrophy (62% vs 26%, p 0.001) and podocyte foot process detachment from the glomerular basement membrane (19% vs 8%, p 0.05), more often thicker (19% vs 5%, p 0.05) and duplicated (26% vs 10%, p 0.05) glomerular basement membrane, and the presence of subendothelial and subepithelial deposits (31% vs 13%, p 0.05). However, in multivariate binary logistic regression analysis, only podocyte hypertrophy (OR 3.14; 95%CI 1.12, 8.79) was an independent risk factor for high-risk progression in IgAN. These findings highlight the importance of podocytopathy in IgAN progression.

X-linked Alport Syndrome with Type IV Collagen α5 Chain Staining Revealing Normal Expression in the Glomerular Basement Membrane and Negative on Bowman's Capsule and Distal Tubular Basement Membrane: A Case Report.

X-linked Alport syndrome is a hereditary progressive renal disease resulting from the disruption of collagen α3α4α5 (IV) heterotrimerization caused by pathogenic variants in the COL4A5 gene. This study aimed to report a male case of X-linked Alport syndrome with a mild phenotype accompanied by an atypical expression pattern of type IV collagen α5 [α5 (IV)] chain in glomerulus. A 38-year-old male presented with proteinuria (2.3 g/day) and hematuria. He has been detected urinary protein and occult blood since childhood. A renal biopsy was performed at the age of 29 years; however, a diagnosis of Alport syndrome was not considered. A renal biopsy 9 years later revealed diffuse thinning and lamellation of the glomerular basement membrane. Α staining for α5 (IV) revealed a normal expression pattern in the glomerular basement membrane and a complete negative expression in Bowman's capsule and distal tubular basement membrane. Using next-generation sequencing, we detected a COL4A5 missense variant within exon 35 (NM_000495.5: c.3088G>A, p. G1030S). The possibility of X-linked Alport syndrome should be considered when negative expression of α5 (IV) staining on Bowman's capsule was observed.

Alport syndrome misdiagnosed with IgA nephropathy from familial history: a case report and brief review.

BACKGROUND: Alport syndrome is a rare inherited disease resulting from a primary disorder of the glomerular basement membrane. This disease results from mutations in genes encoding alpha chains of type IV collagen. In the differential diagnosis of this disease, IgA nephropathy is the most common primary glomerular disease with gross or microscopic hematuria. CASE PRESENTATION: A 50-year-old woman was presented with microscopic hematuria and proteinuria of under one gram. Due to the diagnosis of IgA nephropathy in family members, she was treated and followed up for 4 years as a possible case of IgA nephropathy. Eye examination and audiometry were normal. She underwent renal biopsy with an exacerbation of proteinuria. There was no finding in favor of IgA nephropathy in the histological examination, but the findings of electron microscopy and family history favored Alport syndrome. CONCLUSIONS: This case demonstrates the importance of accurate history and electron microscopy in the complete histological evaluation and diagnosis of glomerular disease. Although in most cases the two can be differentiated based on clinical manifestations, laboratory findings, and histopathological examination, sometimes the association of these two diseases in the families involved or the lack of accurate history and complete histological examinations can complicate the diagnosis.

Functional and morphological renal changes in a Göttingen Minipig model of obesity-related and diabetic nephropathy.

Obesity-related glomerulopathy and diabetic nephropathy (DN) are serious complications to metabolic syndrome and diabetes. The purpose was to study effects of a fat, fructose and cholesterol-rich (FFC) diet with and without salt in order to induce hypertension on kidney function and morphology in Göttingen Minipigs with and without diabetes. Male Göttingen Minipigs were divided into 4 groups: SD (standard diet, n = 8), FFC (FFC diet, n = 16), FFC-DIA (FFC diet + diabetes, n = 14), FFC-DIA + S (FFC diet with extra salt + diabetes, n = 14). Blood and urine biomarkers, glomerular filtration rate (GFR), blood pressure (BP) and resistive index (RI) were evaluated after 6-7 months (T1) and 12-13 months (T2). Histology, electron microscopy and gene expression (excluding FFC-DIA + S) were evaluated at T2. All groups fed FFC-diet displayed obesity, increased GFR and RI, glomerulomegaly, mesangial expansion (ME) and glomerular basement membrane (GBM) thickening. Diabetes on top of FFC diet led to increased plasma glucose and urea and proteinuria and tended to exacerbate the glomerulomegaly, ME and GBM thickening. Four genes (CDKN1A, NPHS2, ACE, SLC2A1) were significantly deregulated in FFC and/or FFC-DIA compared to SD. No effects on BP were observed. Göttingen Minipigs fed FFC diet displayed some of the renal early changes seen in human obesity. Presence of diabetes on top of FFC diet exacerbated the findings and lead to changes resembling the early phases of human DN.

Proprotein convertase subtilisin/kexin type 6 (PCSK6) is a likely antigenic target in membranous nephropathy and nonsteroidal anti-inflammatory drug use.

Drugs are an important secondary cause of membranous nephropathy (MN) with the most common drugs associated with MN being nonsteroidal anti-inflammatory drugs (NSAIDs). Since the target antigen in NSAID-associated MN is not known, we performed laser microdissection of glomeruli followed by mass spectrometry (MS/MS) in 250 cases of PLA2R-negative MN to identify novel antigenic targets. This was followed by immunohistochemistry to localize the target antigen along the glomerular basement membrane and western blot analyses of eluates of frozen biopsy tissue to detect binding of IgG to the novel antigenic target. MS/MS studies revealed high total spectral counts of a novel protein Proprotein Convertase Subtilisin/Kexin Type 6 (PCSK 6) in five of the 250 cases in the discovery cohort. A validation cohort using protein G immunoprecipitation, MS/MS, and immunofluorescence detected PCSK6 in eight additional cases. All cases were negative for known antigens. Ten of 13 cases had a history of heavy NSAID use with no history available in one case. The mean serum creatinine and proteinuria at kidney biopsy were 0.93 ± 0.47 mg/dL and 6.5 ± 3.3 gms/day, respectively. Immunohistochemistry/immunofluorescence showed granular staining for PCSK6 along the glomerular basement membrane, and confocal microscopy showed co-localization of IgG and PCSK6. IgG subclass analysis in three cases revealed codominance of IgG1 and IgG4. Western blot analysis using eluates from frozen tissue showed IgG binding to PCSK6 in PCSK6-associated but not in PLA2R-positive MN. Thus, PCSK6 may be a likely novel antigenic target in MN in patients with prolonged NSAID use.

Thin Basement Membrane: An Underrated Cause of End-Stage Renal Disease.

The term "thin basement membrane" (TBM) refers to a glomerular disorder characterized by diffuse uniform thinning of the glomerular basement membrane (GBM) on electron microscopy. Patients with TBM usually show an isolated hematuria with excellent renal prognosis. However, some patients can develop proteinuria and progressive kidney dysfunction in the long term. Most patients with TBM are heterozygous for pathogenic variants in genes encoding for both the α3 and α4 chains of collagen IV, a major constituent of GBM. Such variants are responsible for a wide range of clinical and histological phenotypes. The differential diagnosis between TBM and autosomal-dominant Alport syndrome and IgA nephritis (IGAN) may be difficult in some cases. Patients who progress to chronic kidney disease may show clinicopathologic features similar to those of primary focal and segmental glomerular sclerosis (FSGS). Without a shared classification of these patients, the risk of misdiagnosis and/or underestimation of the risk of progressive kidney disease is real. New efforts are needed to understand the determinants of renal prognosis and recognize the early signs of renal deterioration, allowing a custom-made diagnosis and therapeutic approach. For this purpose, a practical and simple clinical approach is supplied.

An atypical anti-GBM disease complicated by idiopathic nodular glomerulosclerosis: Case report.

Both atypical anti-glomerular basement membrane (anti-GBM) disease and idiopathic nodular glomerulosclerosis are rare diseases. We report a case of a 53-year-old non-diabetic male who presented with leg edema, nephritic range proteinuria, microscopic hematuria, and decreased renal function. The renal biopsy demonstrated membranoproliferative glomerulonephritis (MPGN) pattern of glomerular injury with focal crescent and segmental nodular glomerulosclerosis. The immunofluorescence studies showed intense linear IgG (IgG1 and IgG4) deposits along the GBM but negative serology. Electron microscopy demonstrated GBM thickening and fibrillar deposition. The presence of MPGN with crescents and the linear IgG along the GBM were consistent with a diagnosis of atypical ant-GBM disease. Superimposed nodular glomerulosclerosis was considered to be idiopathic by excluding other glomerular diseases characterized by fibrillar deposition and nodular glomerulosclerosis. Both diseases were found to have a strong causative association with patient's history of long-term heavy smoking. This unusual case with combination of atypical anti-GBM disease and idiopathic nodular glomerulosclerosis, has brought great challenge for the diagnosis and also made the clinical course highly complicated. This nodular glomerulosclerosis with anti-GBM-like glomerulonephritis may represent a distinct pattern of kidney injury observed in heavy smokers.

Hilar lymphadenopathy, development of tubulointerstitial nephritis, and dense deposit disease following Pfizer-BioNTech COVID-19 vaccination.

Despite the reports on glomerulonephritis associated with COVID-19 mRNA vaccines, no study has reported about the dense deposit disease (DDD). Here, we present a case of hilar lymphadenopathy after the COVID-19 mRNA vaccination, following which the patient developed tubulointerstitial nephritis (TIN) and DDD. A 74-year-old man received his second dose of mRNA vaccine, and on the next day, he developed fever, urticaria, and dyspnea. On further examination, he had pleural effusion and right hilar lymphadenopathies, which were improved with conservative therapy. After 48 days of the second vaccination, he developed renal dysfunction and new-onset hematuria. Light microscopy findings by renal biopsy revealed apparent mesangial cell proliferation, increased mesangial matrix in the glomeruli, and diffuse inflammatory cell infiltration in the interstitium. Immunofluorescence analysis revealed 1 + positive results for IgG and IgM, negative results for IgA, and 2 + positive results for C3 with a garland pattern on the capillary walls. Electron microscopy revealed that severe cell proliferation in the capillary rumen, and continuous, thickened, and highly dark-stained spotty dense deposits in the glomerular basement membrane; and noncontinuous spotty dense deposits in the tubular basement membrane. Based on the decrease in C3 and pathological findings, TIN accompanied with DDD was diagnosed. The mRNA vaccine might have contributed to the development of lymphadenopathies, TIN, and DDD in this case. Moreover, TIN and DDD might be associated with the activated alternative pathway induced by the mRNA vaccine.

[Electron microscopy in nephropathology]. / Elektronenmikroskopie in der Nephropathologie.

Non-neoplastic kidney diseases represent a broad spectrum of diseases. Although their pathogenesis differs, the histological findings may be similar in terms of conventional morphology. A precise classification of these diseases is a prerequisite for correct therapy and prognostic assessment. In the diagnostic process, the magnification achieved by electron microscopy is essential and cannot be replaced by any other technique. The most frequent diagnostic questions addressed by ultrastructural studies represent (1) alterations of podocytes (e.g., minimal-change disease), (2) changes of the thickness and structure of the glomerular basement membrane (e.g., diabetic glomerulosclerosis or Alport disease), (3) the presence, characteristics and exact localisation of immune complexes (e.g., membranous glomerulonephritis or lupus nephritis), (4) alterations of endothelial cells and capillaries (e.g., thrombotic microangiopathy) and (5) diseases of the tubular cells (e.g., light-chain nephropathy or toxic effects). Therefore, ultrastructural investigations are-together with conventional microscopy and immunohistochemistry (or immunofluorescence)-an integral part of the so-called triple-diagnostics in routine nephropathology.

Focal segmental glomerulosclerosis and proteinuria associated with Myo1E mutations: novel variants and histological phenotype analysis.

BACKGROUND: Pathogenic mutations in the non-muscle single-headed myosin, myosin 1E (Myo1e), are a rare cause of pediatric focal segmental glomerulosclerosis (FSGS). These mutations are biallelic, to date only reported as homozygous variants in consanguineous families. Myo1e regulates the actin cytoskeleton dynamics and cell adhesion, which are especially important for podocyte functions. METHODS: DNA and RNA sequencing were used to identify novel MYO1E variants associated with FSGS. We studied the effects of these variants on the localization of Myo1e in kidney sections. We then analyzed the clinical and histological observations of all known pathogenic MYO1E variants. RESULTS: We identified a patient compound heterozygote for two novel variants in MYO1E and a patient homozygous for a deletion of exon 19. Computer modeling predicted these variants to be disruptive. In both patients, Myo1e was mislocalized. As a rule, pathogenic MYO1E variants map to the Myo1e motor and neck domain and are most often associated with steroid-resistant nephrotic syndrome in children 1-11 years of age, leading to kidney failure in 4-10 years in a subset of patients. The ultrastructural features are the podocyte damage and striking diffuse and global Alport-like glomerular basement membrane (GBM) abnormalities. CONCLUSIONS: We hypothesize that MYO1E mutations lead to disruption of the function of podocyte contractile actin cables resulting in abnormalities of the podocytes and the GBM and dysfunction of the glomerular filtration barrier. The characteristic clinicopathological data can help to tentatively differentiate this condition from other genetic podocytopathies and Alport syndrome until genetic testing is done. A higher resolution version of the Graphical abstract is available as Supplementary information.

Genetic Variants of the COL4A3 , COL4A4 , and COL4A5 Genes Contribute to Thinned Glomerular Basement Membrane Lesions in Sporadic IgA Nephropathy Patients.

BACKGROUND: Thinned glomerular basement membrane (tGBM) lesions are not uncommon in IgA nephropathy (IgAN). Type IV collagen-built of α 3, α 4, and α 5 chains, encoded by COL4A3 / COL4A4 / COL4A5 genes-is the major component of glomerular basement membrane (GBM). In recent years, mutations in type IV collagen-encoding genes were also reported in patients with a histologic diagnosis of FSGS. Pathogenic COL4A3 / COL4A4 / COL4A5 variants were recently identified in familial cases of IgAN, but the contribution of these variants to sporadic IgAN is still unclear. METHODS: We compared 161 patients with sporadic IgAN with tGBM lesions (IgAN-tGBM) to matched patients with IgAN without tGBM lesions and matched patients with thin basement membrane nephropathy (TBMN). Variants of COL4A3 / COL4A4 / COL4A5 genes were screened and evaluated after whole-exome sequencing. GBM thickness was measured, and levels of circulating galactose-deficient IgA1 (Gd-IgA1) were assessed by ELISA. RESULTS: The patients with IgAN-tGBM manifested milder disease than did patients with IgAN without tGBM but had more severe features than the patients with TBMN. Exome sequence analysis of the 122 patients with IgAN-tGBM identified 37 diagnostic variants of the COL4A3 / COL4A4 / COL4A5 genes among 38 patients (31.1%). Furthermore, patients with IgAN-tGBM who had diagnostic variants had higher proportions of GBM thickness <250 nm and milder glomerular injury, whereas patients with IgAN-tGBM who did not have diagnostic variants showed more characteristic features of IgAN, including higher intensity of glomerular IgA deposits and elevated Gd-IgA1 levels. These findings suggest different mechanisms in patients with versus without diagnostic variants of these collagen genes. CONCLUSIONS: COL4A3 / COL4A4 / COL4A5 variant detection is essential in evaluating patients with sporadic IgAN with tGBM lesions.

Understanding the podocyte immune responses in proteinuric kidney diseases: from pathogenesis to therapy.

The glomerular filtration barrier, comprising the inner layer of capillary fenestrated endothelial cells, outermost podocytes, and the glomerular basement membrane between them, plays a pivotal role in kidney function. Podocytes, terminally differentiated epithelial cells, are challenging to regenerate once injured. They are essential for maintaining the integrity of the glomerular filtration barrier. Damage to podocytes, resulting from intrinsic or extrinsic factors, leads to proteinuria in the early stages and eventually progresses to chronic kidney disease (CKD). Immune-mediated podocyte injury is a primary pathogenic mechanism in proteinuric glomerular diseases, including minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and lupus nephritis with podocyte involvement. An extensive body of evidence indicates that podocytes not only contribute significantly to the maintenance of the glomerular filtration barrier and serve as targets of immune responses but also exhibit immune cell-like characteristics, participating in both innate and adaptive immunity. They play a pivotal role in mediating glomerular injury and represent potential therapeutic targets for CKD. This review aims to systematically elucidate the mechanisms of podocyte immune injury in various podocyte lesions and provide an overview of recent advances in podocyte immunotherapy. It offers valuable insights for a deeper understanding of the role of podocytes in proteinuric glomerular diseases, and the identification of new therapeutic targets, and has significant implications for the future clinical diagnosis and treatment of podocyte-related disorders.

Clinicopathological characteristics and outcome predictors of anti-glomerular basement membrane glomerulonephritis.

OBJECTIVE: To explore the clinicopathological features of anti-glomerular basement membrane (anti-GBM) glomerulonephritis (anti-GBM-GN) and the prognostic values of clinical and laboratory indicators at diagnosis on renal and patient survival. METHODS: A total of 76 patients (34 males and 42 females) with anti-GBM-GN who were hospitalized in the First Affiliated Hospital of Nanjing Medical University between January 2010 and June 2021 were included in this study. The baseline clinical features, histopathological data from renal biopsies, and predictors of renal and patient survival were retrospectively analyzed. RESULTS: Among the 76 patients, the median serum creatinine at diagnosis was 618.0 (350.98, 888.25) µmol/L and the median estimated glomerular filtration rate (eGFR) was 6.62 (4.39, 14.41) mL/min. Of these 76 patients, 55 (72.4%) received initial kidney replacement therapy (KRT) and 39 (51.3%) received plasma exchange or double-filtered plasmapheresis (DFPP). During a median follow-up duration of 28.5 (6.0, 71.8) months, 53 (69.7%) patients progressed to kidney failure with replacement therapy (KFRT) and received maintenance dialysis. Initial KRT (HR = 3.48, 95% CI = 1.22-9.97, p = 0.020) was a significant risk factor for renal survival. During the follow-up, 49 (64.5%) of 76 patients survived. Age (≥60 years, HR = 4.13, 95% CI = 1.65-10.38, p = 0.003) and initial KRT (HR = 2.87, 95% CI = 1.01-8.14, p = 0.047) were predictive of patient survival. CONCLUSIONS: Among patients with anti-GBM-GN, initial KRT at presentation was predictive of KFRT while older age and initial KRT were associated with higher all-cause mortality.