Charting new frontiers in IgA nephropathy: a paradigm shift toward precision medicine and early intervention?

Advancements in glomerular transcriptomics offer a promising avenue toward precision medicine in IgA nephropathy. Traditional prognostic biomarkers, including proteinuria, blood pressure, and histomorphometry, fall short at capturing the complexity of IgA nephropathy and can only crudely guide therapeutic decisions. This issue needs to be addressed urgently as pathway-specific treatments become available. Glomerular transcriptomics, although technically challenging, offers an opportunity to refine prognostic precision and identify therapeutic targets, even when apparent risk of disease progression is low.

Glomerular transcriptomics predicts long term outcome and identifies therapeutic strategies for patients with assumed benign IgA nephropathy.

Some patients diagnosed with benign IgA nephropathy (IgAN) develop a progressive clinical course, not predictable by known clinical or histopathological parameters. To assess if gene expression can differentiate between progressors and non-progressors with assumed benign IgAN, we tested microdissected glomeruli from archival kidney biopsy sections from adult patients with stable clinical remission (21 non-progressors) or from 15 patients that had undergone clinical progression within a 25-year time frame. Based on 1 240 differentially expressed genes from patients with suitable sequencing results, we identified eight IgAN progressor and nine non-progressor genes using a two-component classifier. These genes, including APOL5 and ZXDC, predicted disease progression with 88% accuracy, 75% sensitivity and 100% specificity on average 21.6 years before progressive disease was clinically documented. APOL lipoproteins are associated with inflammation, autophagy and kidney disease while ZXDC is a zinc-finger transcription factor modulating adaptive immunity. Ten genes from our transcriptomics data overlapped with an external genome wide association study dataset, although the gene set enrichment test was not statistically significant. We also identified 45 drug targets in the DrugBank database, including angiotensinogen, a target of sparsentan (dual antagonist of the endothelin type A receptor and the angiotensin II type 1 receptor) currently investigated for IgAN treatment. Two validation cohorts were used for substantiating key results, one by immunohistochemistry and the other by nCounter technology. Thus, glomerular mRNA sequencing from diagnostic kidney biopsies from patients with assumed benign IgAN can differentiate between future progressors and non-progressors at the time of diagnosis.

A phase 2b, randomized, double-blind, placebo-controlled, clinical trial of atacicept for treatment of IgA nephropathy.

Atacicept is a first-in-class, dual anti-B-cell Activation Factor-A Proliferation-Inducing Ligand fusion protein in clinical evaluation for treatment of IgA nephropathy. To compare efficacy and safety of atacicept versus placebo in patients with IgAN, this randomized, double-blind, placebo-controlled phase 2b clinical trial ORIGIN enrolled 116 individuals with biopsy-proven IgA nephropathy. Participants were randomized to atacicept 150, 75, or 25 mg versus placebo once weekly for up to 36 weeks. Primary and key secondary endpoints were changes in urine protein creatinine ratio based on 24-hour urine collection at weeks 24 and 36, respectively, in the combined atacicept 150 mg and 75 mg group versus placebo. The primary endpoint was met at week 24 as the mean urine protein creatinine ratio was reduced from baseline by 31% in the combined atacicept group versus 8% with placebo, resulting in a significant 25% reduction with atacicept versus placebo. At week 36, the key secondary endpoint was met as the mean urine protein creatinine ratio reduced from baseline by 34% in the combined atacicept group versus a 2% increase with placebo, resulting in a significant 35% reduction with atacicept versus placebo. The reduction in proteinuria was accompanied by stabilization in endpoint eGFR with atacicept compared to a decline with placebo at week 36, resulting in significant between-group geometric mean difference of 11%, approximating an absolute difference of 5.7 mL/min/1.73m2. Endpoint galactose deficient IgA1 levels significantly decreased from baseline by 60% versus placebo. The safety profile of atacicept was like placebo. Thus, our results provide evidence to support a pivotal, phase 3 study of atacicept in IgA nephropathy.

Evidence from the large VALIGA cohort validates the subclassification of focal segmental glomerulosclerosis in IgA nephropathy.

Evidence from the Oxford IgA nephropathy (IgAN) cohort supports the clinical value of subclassifying focal segmental glomerulosclerosis lesions (S1). Using the larger Validation in IgA (VALIGA) study cohort, we investigated the association between podocytopathic changes and higher proteinuria, kidney outcome and response to immunosuppressive therapy. All biopsies were evaluated for glomeruli with segmental capillary occlusion by matrix ("not otherwise specified", NOS lesion), simple capsular adhesion without capillary occlusion (Adh), tip lesions, and podocyte hypertrophy (PH). S1 required a NOS lesion and/or Adh. A Chi-Squared Automatic Interaction Detection method was used to identify subgroups of FSGS lesions associated with distinctive proteinuria at biopsy. We assessed survival from a combined event (kidney failure or 50% decline in estimated glomerular filtration rate). Finally, we evaluated within each subgroup if immunosuppression was associated with a favorable outcome using propensity analysis. In 1147 patients, S1 was found in 70% of biopsies. Subclassification found NOS lesions in 44%, Adh in 59%, PH in 13%, and tip lesions in 3%, with much overlap. Four subgroups were identified with progressively higher proteinuria: from lowest, S1 without NOS, S1 with NOS but without Adh/PH, to highest, S1 with NOS and Adh but without PH, and S1 with NOS and PH. These four subgroups showed progressively worse kidney survival. Immunosuppression was associated with a better outcome only in the two highest proteinuria subgroups. Propensity analysis in these two groups, adjusted for clinical and pathological findings, found a significantly reduced time-dependent hazard of combined outcome with corticosteroids. Podocyte hypertrophy and glomeruli with simple adhesions appeared to reflect active lesions associated with a response to corticosteroids, while other S1 lesions defined chronicity. Thus, our findings support subclassifying S1 lesions in IgAN.

Time-Varying Proteinuria and Progression of IgA Nephropathy: A Cohort Study.

RATIONALE & OBJECTIVE: Proteinuria is a surrogate end point for predicting long-term kidney outcomes in IgA nephropathy (IgAN) with levels<1g/day identified as a therapeutic target. However, this threshold has not been sufficiently studied. We quantified the associations of progression of IgAN with various levels of proteinuria. STUDY DESIGN: Observational cohort study. SETTING & PARTICIPANTS: 1,530 patients with IgAN and at least 12 months of follow-up at Peking University First Hospital. EXPOSURE: Proteinuria levels updated over time (time-varying proteinuria, TVP). OUTCOME: A composite kidney outcome of a 50% reduction in the estimated glomerular filtration rate or end-stage kidney disease. ANALYTICAL APPROACH: Marginal structural models. RESULTS: After a median follow-up period of 43.5 (IQR, 27.2-72.8) months, 254 patients (16.6%) developed the composite kidney outcome. A graded association was observed between TVP and composite kidney outcomes with higher risk among those with proteinuria of≥0.5g/day. Compared with TVP<0.3g/day, the HRs for proteinuria levels of 0.3 to<0.5g/day, 0.5 to<1.0g/day, 1.0 to<2.0g/day, and≥2.0g/day were 2.22 (95% CI, 0.88-5.58), 4.04 (95% CI, 1.93-8.46), 8.46 (95% CI, 3.80-18.83), and 38.00 (95% CI, 17.62-81.95), respectively. The trend was more pronounced in patients with baseline proteinuria of≥1.0g/day, among whom a higher risk was observed with TVP of 0.3 to<0.5g/day compared with TVP<0.3g/day (HR, 3.26 [95% CI, 1.07-9.92], P=0.04). However, in patients with baseline proteinuria levels of<1g/day, the risk of composite kidney outcome only began to increase when TVP was≥1.0g/day (HR, 3.25 [95% CI, 1.06-9.90]). LIMITATIONS: Single-center observational study, selection bias, and unmeasured confounders. CONCLUSIONS: This study showed that patients with IgAN and proteinuria levels of>0.5g/day, have an elevated risk of kidney failure especially among patients with proteinuria levels≥1.0g/day before initiating treatment. These data may serve to inform the selection of proteinuria targets in the treatment of IgAN. PLAIN-LANGUAGE SUMMARY: The presence of proteinuria has often been considered a surrogate end point and a possible therapeutic target in clinical trials in IgA nephropathy (IgAN). Some guidelines recommend a reduction in proteinuria to<1g/day as a treatment goal based on the results of previous longitudinal studies. However, these findings may have been biased because they did not properly adjust for time-dependent confounders. Using marginal structural models to appropriately account for these confounding influences, we observed that patients with IgAN and proteinuria levels≥0.5g/day have an elevated risk of kidney failure, especially among patients who had proteinuria levels of≥1.0g/day before initiating treatment. These data may serve to inform the selection of proteinuria targets in the treatment of IgAN.

Urinary Plasminogen as a Marker of Disease Progression in Human Glomerular Disease.

RATIONALE & OBJECTIVE: Glomerular disorders have a highly variable clinical course, and biomarkers that reflect the molecular mechanisms underlying their progression are needed. Based on our previous work identifying plasminogen as a direct cause of podocyte injury, we designed this study to test the association between urine plasmin(ogen) (ie, plasmin and its precursor plasminogen) and end-stage kidney disease (ESKD). STUDY DESIGN: Multicenter cohort study. SETTING & PARTICIPANTS: 1,010 patients enrolled in the CureGN Cohort with biopsy-proven glomerular disease (focal segmental glomerulosclerosis, membranous nephropathy, and immunoglobulin A nephropathy). PREDICTORS: The main predictor was urine plasmin(ogen) at baseline. Levels were measured by an electrochemiluminescent immunoassay developed de novo. Traditional clinical and analytical characteristics were used for adjustment. The ratio of urine plasmin(ogen)/expected plasmin(ogen) was evaluated as a predictor in a separate model. OUTCOME: Progression to ESKD. ANALYTICAL APPROACH: Cox regression was used to examine the association between urinary plasmin(ogen) and time to ESKD. Urinary markers were log2 transformed to approximate normal distribution and normalized to urinary creatinine (Log2uPlasminogen/cr, Log2 urinary protein/cr [UPCR]). Expected plasmin(ogen) was calculated by multiple linear regression. RESULTS: Adjusted Log2uPlasminogen/cr was significantly associated with ESKD (HR per doubling Log2 uPlasminogen/cr 1.31 [95% CI, 1.22-1.40], P<0.001). Comparison of the predictive performance of the models including Log2 uPlasminogen/cr, Log2 UPCR, or both markers showed the plasmin(ogen) model superiority. The ratio of measured/expected urine plasmin(ogen) was independently associated with ESKD: HR, 0.41 (95% CI, 0.22-0.77) if ratio<0.8 and HR 2.42 (95% CI, 1.54-3.78) if ratio>1.1 (compared with ratio between 0.8 and 1.1). LIMITATIONS: Single plasmin(ogen) determination does not allow for the study of changes over time. The use of a cohort of mostly white patients and the restriction to patients with 3 glomerular disorders limits the external validity of our analysis. CONCLUSIONS: Urinary plasmin(ogen) and the ratio of measured/expected plasmin(ogen) are independently associated with ESKD in a cohort of patients with glomerular disease. Taken together with our previous experimental findings, urinary plasmin(ogen) could be a useful biomarker in prognostic decision making and a target for the development of novel therapies in patients with proteinuria and glomerular disease. PLAIN-LANGUAGE SUMMARY: Glomerular diseases are an important cause of morbidity and mortality in patients of all ages. Knowing the individual risk of progression to dialysis or transplantation would help to plan the follow-up and treatment of these patients. Our work studies the usefulness of urinary plasminogen as a marker of progression in this context, since previous studies indicate that plasminogen may be involved in the mechanisms responsible for the progression of these disorders. Our work in a sample of 1,010 patients with glomerular disease demonstrates that urinary plasminogen (as well as the ratio of measured to expected plasminogen) is associated with the risk of progression to end-stage kidney disease. Urine plasminogen exhibited good performance and, if further validated, could enable risk stratification for timely interventions in patients with proteinuria and glomerular disease.

Differentiated metabolomic profiling reveals plasma amino acid signatures for primary glomerular disease.

Primary glomerular disease (PGD) is an idiopathic cause of renal glomerular lesions that is characterized by proteinuria or hematuria and is the leading cause of chronic kidney disease (CKD). The identification of circulating biomarkers for the diagnosis of PGD requires a thorough understanding of the metabolic defects involved. In this study, ultra-high performance liquid chromatography-tandem mass spectrometry was performed to characterize the amino acid (AA) profiles of patients with pathologically diagnosed PGD, including minimal change disease (MCD), focal segmental glomerular sclerosis (FSGS), membranous nephropathy, and immunoglobulin A nephropathy. The plasma concentrations of asparagine and ornithine were low, and that of aspartic acid was high, in patients with all the pathologic types of PGD, compared to healthy controls. Two distinct diagnostic models were generated using the differential plasma AA profiles using logistic regression and receiver operating characteristic analyses, with areas under the curves of 1.000 and accuracies up to 100.0% in patients with MCD and FSGS. In conclusion, the progression of PGD is associated with alterations in AA profiles, The present findings provide a theoretical basis for the use of AAs as a non-invasive, real-time, rapid, and simple biomarker for the diagnosis of various pathologic types of PGD.

Association between urinary C4d levels and disease progression in IgA nephropathy.

BACKGROUND: C4d mesangial deposition, a hallmark of lectin pathway activation in immunoglobulin A nephropathy (IgAN), has been shown to be associated with risk of kidney failure. To date, the relationship between urinary C4d and renal outcome remain unelucidated. METHODS: A total of 508 patients with biopsy-proven IgAN were enrolled in this study, whose baseline urine samples at the time of biopsy were collected and the levels of urinary C4d were quantified by enzyme-linked immunosorbent assay. The time-averaged C4d (TA-C4d) and the change in proteinuria were measured in sequential urine samples obtained from IgAN patients. The kidney progression event was defined as a 50% estimated glomerular filtration rate (eGFR) decline or end-stage kidney disease or death. RESULTS: After a median follow-up of 36 months, 70 (13.8%) of the participants reached the kidney progression event. Higher levels of urinary C4d/Ucr were found to be associated with decreased eGFR, massive proteinuria, lower serum albumin levels, hypertension, and severe Oxford E and T scores. Upon adjusting for traditional risk factors (including demographics, eGFR, proteinuria, hypertension, Oxford pathologic score and immunosuppressive therapy), elevated levels of urinary C4d/Ucr were independently associated with an increased risk of chronic kidney disease progression [adjusted hazard ratio (HR) per standard deviation increment of log-transformed C4d/Ucr: 1.46; 95% CI 1.04-2.06; P = .030]. In reference to the low C4d group, the risk of poor renal outcome increased for the high C4d group (adjusted HR 1.93; 95% CI 1.05-3.54; P = .033). Additionally, a low baseline C4d level was independently associated with a favorable proteinuria response to immunosuppressive therapy at 3 months (adjusted relative risk 2.20; 95% CI 1.04-4.63, P = .038). CONCLUSION: The urinary C4d, serving as a non-invasive biomarker, is associated with the progression of IgAN and holds the potential to predict proteinuria response in this disease.

Identification of inflammatory biomarkers in IgA nephropathy using the NanoString technology: a validation study in Caucasians.

OBJECTIVE AND DESIGN: Immunoglobulin A nephropathy (IgAN) is a kidney disease characterized by the accumulation of IgA deposits in the glomeruli of the kidney, leading to inflammation and damage to the kidney. The inflammatory markers involved in IgAN remain to be defined. Gene expression analysis platforms, such as the NanoString nCounter system, are promising screening and diagnostic tools, especially in oncology. Still, their role as a diagnostic and prognostic tool in IgAN remains scarce. In this study, we aimed to validate the use of NanoString technology to identify potential inflammatory biomarkers involved in the progression of IgAN. SUBJECTS: A total of 30 patients with biopsy-proven IgAN and 7 cases of antineutrophil cytoplasmic antibody (ANCA)-associated pauci-immune glomerulonephritis were included for gene expression measurement. For the immunofluorescence validation experiments, a total of 6 IgAN patients and 3 controls were included. METHODS: Total RNA was extracted from formalin-fixed paraffin-embedded kidney biopsy specimens, and a customized 48-plex human gene CodeSet was used to study 29 genes implicated in different biological pathways. Comparisons in gene expression were made between IgAN and ANCA-associated pauci-immune glomerulonephritis patients to delineate an expression profile specific to IgAN. Gene expression was compared between patients with low and moderate risk of progression. Genes for which RNA expression was associated with disease progression were analyzed for protein expression by immunofluorescence and compared with controls. RESULTS: IgAN patients had a distinct gene expression profile with decreased expression in genes IL-6, INFG, and C1QB compared to ANCA patients. C3 and TNFRSF1B were identified as potential biomarkers for IgAN progression in patients early in their disease course. Protein expression for those 2 candidate genes was upregulated in IgAN patients compared to controls. Expression of genes implicated in fibrosis (PTEN, CASPASE 3, TGM2, TGFB1, IL2, and TNFRSF1B) was more pronounced in IgAN patients with severe fibrosis compared to those with none. CONCLUSIONS: Our findings validate our NanoString mRNA profiling by examining protein expression levels of two candidate genes, C3 and TNFRSF1B, in IgAN patients and controls. We also identified several upregulated mRNA transcripts implicated in the development of fibrosis that may be considered fibrotic markers within IgAN patients.

Alterations in oxidative stress biomarkers and helper T-cell subgroups in patients with periodontitis and IgA nephropathy.

OBJECTIVE: Investigating the changes in the oxidative stress levels and helper T lymphocyte (Th) subsets in patients with periodontitis and IgA nephropathy (IgAN) to determine their relationship. BACKGROUND: IgAN has a high prevalence, poor prognosis, and no effective cure. Accumulating evidence has implicated a close relationship between periodontitis and chronic kidney diseases, in which both IgAN and chronic periodontitis show chronic inflammation and abnormal metabolism. However, few studies have been conducted on the relationship between the two diseases from this perspective. METHODS: We divided 86 IgAN patients into patients with healthy periodontium (IgAN-H, n = 34) and patients with periodontitis IgAN (IgAN-P, n = 52); moreover, we divided 72 systemically healthy participants into patients with periodontitis (H-P, n = 35) and participants with healthy periodontium (H-H, n = 37). The proportions of Th subsets in peripheral blood were estimated using flow cytometry. Cytokine levels in plasma were assessed using cytokine assay kits. Enzyme-linked immunosorbent assay was used to evaluate the plasma levels of oxidative stress. RESULTS: Our results from analyzing the Th cell subsets indicated that Th2 cell counts in the IgAN-P group were significantly lower than those in the IgAN-H group, while Th17 cell counts were increased (p < 0.05). Moreover, the Th1/Th2 ratio and interleukin-6 levels in the IgAN-P group were significantly higher than those in the H-H group (p < 0.01). Compared with that in the H-H group, in the remaining three groups, plasma total oxidation state (TOS) levels were increased (p < 0.01), while plasma total antioxidant state (TAS) levels were decreased (p < 0.05). Furthermore, estimated glomerular filtration rate was negatively correlated with the probing depth and gingival bleeding index. IgAN was a risk factor for periodontitis, while TAS was a protective factor for periodontitis. The oxidative stress index (OSI) might be valuable for distinguishing periodontitis patients from healthy controls (area under the receiver operator characteristic curve = 0.951). CONCLUSION: IgAN is an independent risk factor of periodontitis, and the Th17 cell-mediated inflammatory response might be associated with the occurrence of periodontitis in patients with IgAN. Patients with coexisting IgAN and periodontitis exhibit increased oxidative stress, in which TOS and OSI are potential biomarkers for diagnosing periodontitis.

Combined Effects of the Serum IgA/C3 Ratio and Glomerular C3 Staining on the Renal Outcome in Adult Immunoglobulin A Nephropathy.

INTRODUCTION: The aim of this study was to evaluate the predictive value of the serum IgA/C3 ratio and glomerular C3 deposits in kidney biopsy in adult IgA nephropathy. METHODS: The study included 718 adult IgAN patients diagnosed based on kidney biopsy. Patients without corticosteroids or immunosuppressive drugs >1 month were regularly followed up for at least 1 year or until the study endpoint. The optimum serum IgA/C3 ratio was calculated by the AUROC-based cutoff ratio. Proteinuria, creatinine, eGFR, serum IgA, and serum C3 were evaluated at baseline. Kidney biopsy was categorized using the Oxford classification, with a calculation of the MEST-C score. The degree of glomerular C3 staining was semiquantitatively determined (grade 0, no or trace; grade 1, mild; grade 2, moderate; grade 3, marked) by immunofluorescence microscopy. The patients were divided into four groups by the serum IgA/C3 ratio and glomerular C3 staining. RESULTS: The baseline data suggested that when the serum IgA/C3 ratio was at the same level, patients with a high glomerular C3 staining score (≥2) always had mesangial proliferation, segmental glomerulosclerosis, and tubular atrophy/interstitial fibrosis (group 1 vs. group 2; group 3 vs. group 4). When glomerular C3 staining was at the same level, proteinuria was significantly higher in patients with serum IgA/C3<2.806 (group 1 vs. group 3; group 2 vs. group 4), which was contrary to previous studies that have suggested that the serum level of IgA/C3 was associated with disease severity. Hence, this study set out to investigate the combined effects of the serum IgA/C3 ratio and glomerular C3 staining on the renal outcome in adult IgA nephropathy. Renal survival analysis indicated that serum IgA/C3 ≥2.806 and glomerular C3 staining ≥2 (group 1) may be correlated with a poorer prognosis, especially in different clinicopathological characteristics of IgAN patients based on the subgroup analysis. Multivariate Cox analysis demonstrated that hypertension, serum creatinine, CKD stage, T1/2 and C3 staining were independent predictive factors of renal survival. CONCLUSIONS: The combination of serum IgA/C3 and C3 staining may contribute to improved optimization of the prognostic model in IgAN patients, especially patients with different sexes and degrees of disease. However, further study is required for validation in the future.

Management and Clinical Outcomes of Membranous Nephropathy, IgA Nephropathy, and Minimal Change Disease Two Years Post-Kidney Biopsy.

INTRODUCTION: This study evaluated the phenotypic and pathology characteristics of patients undergoing kidney biopsy at a single center, while also determining the frequency and factors associated with clinical outcomes. METHODS: The incidence and distribution of biopsy-proven kidney diseases in 2000-2019 were surveyed. Consecutive individuals diagnosed with membranous nephropathy (MN), immunoglobulin A nephropathy (IgAN), and minimal change disease (MCD) between August 2015 and December 2019 were enrolled in the prospective 2-year follow-up study. Outcomes included remission of proteinuria and kidney disease progression events. Multivariable-adjusted Cox proportional hazards model was applied. RESULTS: 4,550 kidney biopsies were performed in 2000-2019, showing a noticeable increase in the proportion of MN. 426 patients were enrolled in the follow-up cohort. 346 (81.2%) achieved remission of proteinuria, 39 (9.2%) suffered kidney disease progression and 51.3% of them were diagnosed with IgAN. Kidney pathological diagnosis (MN vs. MCD: hazard ratio [HR], 0.42; 95% confidence interval [95% CI], 0.31-0.57; IgAN vs. MCD: 0.58; 0.39-0.85), levels of 24-h urine protein at biopsy (1.04; 1.00-1.08) and presence of nodular mesangial sclerosis (0.70; 0.49-0.99) were significantly correlated with remission of proteinuria after adjusting for baseline variables. 24-h urine protein levels at biopsy (1.14; 1.04-1.25) and the presence of crescents (2.30; 1.06-4.95) were the independent risk factors for kidney disease progression events after adjusting for baseline variables. CONCLUSION: The increasing frequency of MN has been affirmed over the past 2 decades. The therapeutic status, clinical outcomes, and factors influencing these outcomes were presented in this single-center study for the three primary glomerular diseases.

Are children with IgA nephropathy different from adult patients?

BACKGROUND: Previously, several studies have indicated that pediatric IgA nephropathy (IgAN) might be different from adult IgAN, and treatment strategies might be also different between pediatric IgAN and adult IgAN. METHODS: We analyzed two prospective cohorts established by pediatric and adult nephrologists, respectively. A comprehensive analysis was performed investigating the difference in clinical and pathological characteristics, treatment, and prognosis between children and adults with IgAN. RESULTS: A total of 1015 children and 1911 adults with IgAN were eligible for analysis. More frequent gross hematuria (88% vs. 20%, p < 0.0001) and higher proteinuria (1.8 vs. 1.3 g/d, p < 0.0001) were seen in children compared to adults. In comparison, the estimated glomerular filtration rate (eGFR) was lower in adults (80.4 vs. 163 ml/min/1.73 m2, p < 0.0001). Hypertension was more prevalent in adult patients. Pathologically, a higher proportion of M1 was revealed (62% vs. 39%, p < 0.0001) in children than in adults. S1 (62% vs. 28%, p < 0.0001) and T1-2 (34% vs. 8%, p < 0.0001) were more frequent in adults. Adjusted by proteinuria, eGFR, and hypertension, children were more likely to be treated with glucocorticoids than adults (87% vs. 45%, p < 0.0001). After propensity score matching, in IgAN with proteinuria > 1 g/d, children treated with steroids were 1.87 (95% CI 1.16-3.02, p = 0.01) times more likely to reach complete remission of proteinuria compared with adults treated with steroids. CONCLUSIONS: Children present significantly differently from adults with IgAN in clinical and pathological manifestations and disease progression. Steroid response might be better in children.

Development and validation of a diagnostic nomogram to evaluate tubular atrophy/interstitial fibrosis of IgA nephropathy.

Background: IgA nephropathy (IgAN) is a cause of chronic kidney disease (CKD). Tubular atrophy/interstitial fibrosis is associated with IgAN prognosis. However, simple tools for predicting pathological lesions of IgAN remain limited. Our objective was to develop a tool for evaluating tubular atrophy/interstitial fibrosis in patients with IgAN. Methods: In this cross-sectional study, 410 biopsy-verified IgAN patients were included. The factors associated with the incident interstitial fibrosis or tubular atrophy in IgAN were confirmed by using logistic regression analysis. A nomogram was developed using logistic regression coefficients to evaluate tubular atrophy or interstitial fibrosis. Receiver operating characteristic curves (ROC) and calibration curves were used to determine the discriminative ability and predictive accuracy of the nomogram. Results: In this study, the IgAN patients with tubular atrophy or interstitial fibrosis were older and had a higher percentage of males, hypertension and urinary protein excretion (UPE), with high levels of serum cystatin C, serum creatinine, high-sensitivity C-reactive protein and serum C4. The eGFRcr-cys equation calculated using serum creatinine, cystatin C and UPE were considered independent influencing factors of tubular atrophy or interstitial fibrosis in patients with IgAN. Furthermore, the nomogram demonstrated good discrimination (AUC: 0.87, 95% CI 0.81 to 0.93) and calibration in the validation cohort. Conclusion: The eGFRcr-cys and UPE are associated with tubular atrophy or interstitial fibrosis in patients with IgAN. Diagnostic nomogram can predict tubular atrophy or interstitial fibrosis in IgAN.

A Review of IgA Vasculitis (Henoch-Schönlein Purpura) Past, Present, and Future.

The clinical association of purpura, arthralgia, and arthritis was first described in 1837 in a publication by Johann Lukas Schönlein, a German physician. In 1874, Eduard Henoch, a student of Schönlein, reported cases of children with purpura, abdominal pain, bloody diarrhea, and joint pain. IgA vasculitis, or Henoch-Schönlein purpura, is a systemic hypersensitivity vasculitis caused by the deposition of immune complexes in small blood vessels, including the renal glomeruli and mesangium. In the skin, the presentation is with non-thrombocytopenic purpura or urticaria. Worldwide, IgA nephropathy is the most common cause of primary glomerulonephritis. Detection of IgA deposition in small blood vessels and the renal glomeruli is diagnostic in most cases. This article aims to review the history, current classification, epidemiology, presentation, and diagnosis of IgA vasculitis and nephropathy, disease associations or trigger factors, including infections, vaccines, and therapeutic agents, and highlights some future approaches to improve diagnosis and clinical management.

Corticosteroid in IgA nephropathy with moderate proteinuria: A retrospective cohort study.

BACKGROUND: Corticosteroids remain contentious as a therapeutic option for IgA nephropathy. We conducted a retrospective cohort study to explore whether corticosteroid therapy is efficient and safe for IgAN patients with moderate proteinuria. METHODS: A total of 336 patients with renal biopsy-confirmed IgAN, estimated glomerular filtration (eGFR) over 15 mL/min/1.73 m2 and urine protein levels of 0.75-3.5 g/d were enrolled. According to the treatment protocol, we classified the enrolled patients into two groups: one receiving corticosteroids and the other receiving supportive care. Complete remission, partial remission, and no remission were applied to describe the efficacy assessments. The endpoint was defined as a 40% reduction in eGFR, the onset of ESRD, or renal disease-related death. RESULTS: Clinical and pathological progression risk factors were higher in corticosteroid-treated individuals. Logistic regression analysis revealed that the corticosteroid group was considerably related to a higher remission rate after adjustment for confounding factors. The occurrence of serious adverse events between the two groups was not found to be statistically significantly different. Then, we matched 95 couples of patients with similar baseline levels in both groups by propensity score matching. The results showed that corticosteroid-treated patients showed higher overall and complete remission rates than untreated patients. However, due to the relatively short follow-up period, no significant differences in the incidence of endpoint and survival analyses have been observed thus far. CONCLUSION: Corticosteroid therapy may benefit IgAN patients with moderate proteinuria via proteinuria reduction and renal function preservation.

Validation of IgA nephropathy diagnosis in the Swedish Renal Registry.

AIM: The Swedish Renal Registry (SRR) is a unique national quality registry that monitors the clinical trajectory of patients with chronic kidney disease (CKD). We have validated the biopsy data registered in the SRR for IgA Nephropathy (IgAN) diagnosis. METHODS: In total 25% of all patients (n = 142), registered with IgAN in the SRR after having performed a kidney biopsy during 2015-2019, were randomly selected. We obtained original biopsy and medical records for 139 (98%) patients. We evaluated the IgAN diagnosis using a standardized template, calculated its positive predictive value (PPV) with 95% confidence interval (CI) and reported clinical features at the time of diagnosis. RESULTS: A histological and clinical diagnosis of IgAN was confirmed in 132 of the 139 patients, yielding a PPV of 95% (95% CI 90-98%). Median age was 46 years (range: 18-85) and the male:female ratio was 2.1:1. The median creatinine level was 123 µmol/L, with a corresponding estimated glomerular filtration rate (eGFR) level of 51 mL/min/1.73m2. Histological features of IgA deposits were seen in all patients, hypercellularity in 102/132 (77.2%), C3 deposits in 98/132 (72.4%) and C1q deposits in 27/132 (20.5%) of the cases. CONCLUSION: Validating data is not research per se, but continuous validation of medical registries is an important feature necessary to ensure reliable data and the foundation of good epidemiological data for future research. Our validation showed a high PPV (95%) for IgAN diagnosis registered in the SRR. Clinical characteristics were consistent with previous reports. The biopsy data in the SRR will be a valuable resource in future IgAN research.

Characteristics of renal pathology and coagulation function in IgA nephropathy and IgA vasculitis associated nephritis.

BACKGROUND: The objective of this study is to investigate the clinical and pathological differences between patients with IgA nephropathy (IgAN) and IgA vasculitis associated nephritis (IgAVN). METHODS: A total of 253 patients with IgAN and 71 patients with IgAVN were retrospectively included in the study, and clinical and laboratory data were collected and analysed. RESULTS: Compared with IgAVN group, months from onset to kidney biopsy were significantly prolonged in IgAN patients because of the lack of obvious symptoms such as rash, abdominal symptoms, and joint pain (13.5 ± 26.6 vs. 10.2 ± 31.6 months, P = 0.007), and the levels of serum creatinine (92.3 ± 94.7 vs. 68.9 ± 69.2 µmol/L, P = 0.015) was higher and eGFR (99.1 ± 35.2 vs. 123.4 ± 41.8 mL/min/1.73m2, P < 0.001) was lower in IgAN group. The pathological results revealed that patients with IgAN have a greater degree of chronic kidney injury compared to patients with IgAVN. In addition, the levels of plasma D-Dimers (1415.92 ± 1774.69 vs. 496.78 ± 711.91 ng/mL, P < 0.001) and fibrinogen degradation products (FDP) (3.92 ± 4.73 vs. 1.63 ± 2.46 µg/mL, P = 0.001) were significantly higher in IgAVN patients than in IgAN patients. The deposition of fibrinogen in the renal tissues was more severe and the cumulative partial remission rate was higher in patients with IgAVN as compared to those with IgAN (P = 0.001). CONCLUSIONS: In comparison, IgAN patients had poorer renal function, whereas IgAVN patients had more severe coagulation abnormalities. These findings provide a basis for the differentiation of the two diseases at an early stage.

Clinical significance of urinary inflammatory biomarkers in patients with IgA nephropathy.

BACKGROUND: IgA nephropathy (IgAN) is the most common type of primary glomerulonephritis, although the definitive markers are unknown. We aimed to investigate the clinical significance of urinary cytokines in patients with IgAN. METHODS: From 2009 to 2018, the patients were divided into three groups: IgAN (n = 191), disease control (n = 53), and normal control (n = 76). We used a multiplex enzyme-linked immunosorbent assay to measure 16 selected urinary inflammatory cytokines, evaluated the correlation between clinical and pathological features following regression analysis on progression. RESULTS: The IgAN group exhibited significantly different levels of urinary cytokines compared to the normal control and disease control groups. Urinary levels of B-cell-activating factor, vascular endothelial growth factor receptor-2, monocyte chemoattractant protein-1, C-X-C motif chemokine 10, C-X-C motif ligand 16, epidermal growth factor (EGF), endocan, endostatin, growth/differentiation factor-15 (GDF-15), interleukin-6 (IL-6), mannose-binding lectin, transferrin receptor, and kidney injury molecule-1 were significantly correlated with both the estimated glomerular filtration rate and urine protein-creatinine ratio. In a multivariate Cox regression analysis, urinary EGF (hazard ratio [HR] 0.40, 95% confidence interval [CI] 0.17-0.95, P = 0.04), GDF-15 (HR 2.45, 95% CI 1.01-5.94, P = 0.048), and IL-6 (HR 3.02, 95% CI 1.05-8.64, P = 0.04) were associated with progression in IgAN. CONCLUSIONS: Urinary inflammatory biomarkers may serve as alternative predictive biomarkers in patients with IgAN. Further studies are needed to elucidate the physiological mechanisms and confirm the results.

Medullary sponge kidney with IgA nephropathy: a case report and literature review.

BACKGROUND: Medullary sponge kidney (MSK)is rare in association with glomerulonephritis. We report a patient with medullary sponge kidney, and the kidney biopsy revealed a diagnosis of IgA nephropathy. CASE PRESENTATION: A 27-year-old female presented with hematuria and proteinuria, and imaging studies indicated the presence of medullary spongy kidney. With appropriate preparation, a kidney biopsy was performed. Considering the patient's clinical and pathological characteristics, the final diagnosis was determined to be medullary sponge kidney associated by IgA nephropathy. The combination of corticosteroids and angiotensin receptor blockers (ARBs) proved to be significantly effective in reducing proteinuria in the current case. To the best of our knowledge, this is the first reported case that demonstrates the coexistence of MSK and IgA nephropathy. CONCLUSIONS: Administering precise therapy based on renal pathology can potentially enhance outcomes for patients with renal conditions, necessitating the need for clinicians to be vigilant about differential diagnosis in order to reduce the rates of missed diagnoses and misdiagnosis.