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Histopathological and electron microscopic spectrum of glomerular diseases in pediatric and adult patients with nephrotic range proteinuria and nephrotic syndrome: A tertiary center study
MD, Vinant Bhargava4DNB, Kanav Anand5MD
*Corresponding author: Pallav Gupta, Department of Histopathology, Sir Ganga Ram Hospital, New Delhi, India. pallavkmc1@gmail.com
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Received: ,
Accepted: ,
How to cite this article: Dharamdasani SS, Osama MA, Gupta P, Bhargava V, Anand K. Histopathological and electron microscopic spectrum of glomerular diseases in pediatric and adult patients with nephrotic range proteinuria and nephrotic syndrome: A tertiary center study. Int J Health Sci (Qassim). 2026;20:23-33. doi: 10.25259/IJHS_108_2025
Abstract
Objectives:
Nephrotic range proteinuria (NRP) and nephrotic syndrome (NS) are common manifestations of glomerular diseases across age groups. Kidney biopsy remains the gold standard for diagnosis. However, in resource-limited settings, the availability of electron microscopy (EM) is restricted, necessitating evaluation of its diagnostic utility. This study aims to assess the histopathological spectrum of glomerular diseases in pediatric and adult patients presenting with NS and NRP, and to evaluate the diagnostic utility of EM.
Methods:
A total of 180 consecutive renal biopsies were analyzed according to the 2016 Renal Pathology Society Consensus guidelines.
Results:
Of the 180 patients, 36 (20%) were pediatric and 144 (80%) were adult. NS was more common in children (72.2%), while nephrotic-range proteinuria (NRP) without full-blown NS predominated among adults (52.8%). In pediatric patients with NS, the most frequent diagnosis was minimal change nephropathy (MCN) (38.5%), followed by focal segmental glomerulosclerosis (FSGS) (19.2%). Among pediatric NRP cases, MCN remained the most common (27.7%), with lupus nephritis (22.3%) and FSGS (16.6%) also notable. In adults with NRP, the leading diagnosis was FSGS (27.1%), followed by IgA nephropathy, membranous nephropathy (MN), and amyloidosis, each accounting for 11.8% of this subgroup. Among adults with NS, FSGS remained predominant (26.5%), followed by amyloidosis (17.6%) and MN (14.7%). EM contributed to diagnosis in 29.4% of all cases (n = 53), being essential for diagnosis in 12.2% and supportive in 17.2%. EM was particularly crucial in identifying lupus podocytopathy, dense deposit disease, Alport syndrome, and early-stage MN, which may not be definitively diagnosed by light or immunofluorescence microscopy alone.
Conclusion:
FSGS and MCN are the most common causes of NS across age groups. The findings highlight a shifting spectrum of glomerular diseases, consistent with national and global trends. Although not routinely feasible, EM provides significant diagnostic value in selected cases. Preserving tissue for potential EM evaluation is strongly recommended, especially in ambiguous or complex presentations.
Keywords
Electron
Glomerular
Immunofluorescence
Microscope
Nephrotic
Pediatric
Proteinuria
INTRODUCTION
Background
Glomerular diseases encompass a wide range of disorders affecting the kidney’s filtering units, often presenting with proteinuria, hematuria, and varying degrees of renal dysfunction. Among these, nephrotic-range proteinuria (NRP) is defined as urinary protein loss exceeding 40 mg/m2/hour in children or ≥3.5 g/day/1.73 m2 in adults. A subset of patients with NRP meet the clinical criteria for nephrotic syndrome (NS), which is characterized by hypoalbuminemia (plasma albumin <3 g/dL in adults, <2.5 g/dL in children), hyperlipidemia (serum cholesterol >200 mg/dL), and generalized edema. A subset of patients with NRP meet the clinical criteria for nephrotic syndrome (NS), which is characterised by hypoalbuminaemia (plasma albumin <3 g/dL in adults, <2.5 g/dL in children), hyperlipidaemia (serum cholesterol >200 mg/dL), and generalised oedema.[1,2] Nephrotic syndrome is a clinical presentation in both paediatric and adult patients, with an annual incidence of 4.7 cases per 100,000 children and 3 cases per 100,000 adults.[3,4] The underlying causes of NS and NRP are diverse and include both primary and secondary glomerular pathologies. Accurate diagnosis of these conditions is essential for guiding treatment and predicting outcomes. While some glomerular diseases have well-defined clinical and histological profiles, considerable overlap often exists, making histopathological evaluation essential. Kidney biopsy remains the gold standard for diagnosis and typically involves light microscopy (LM), immunofluorescence (IF), and electron microscopy (EM). LM provides insight into structural changes such as hypercellularity and sclerosis, while IF is useful for detecting immune complex deposition. EM offers ultrastructural detail that is critical for identifying features such as podocyte foot process effacement, basement membrane alterations, and organized deposits that may not be visible on LM or IF alone.
Knowledge gap
In the Indian context, access to comprehensive biopsy analysis, particularly EM, is often constrained by cost, technical limitations, and infrastructure availability. As a result, many diagnoses rely heavily on LM and IF alone, which may not be sufficient in complex or ambiguous cases. Although some regional studies have attempted to characterize the histopathological patterns of glomerular diseases, there is a paucity of research that systematically evaluates the contribution of EM, especially in the context of NS and NRP. The gap is even more pronounced in the pediatric population, where early diagnosis is vital for long-term renal preservation. Furthermore, recent advances in the classification of glomerular diseases – including the identification of entities such as C3 glomerulopathy and genetic podocytopathies – highlight the need for updated and comprehensive diagnostic strategies that include EM.
Rationale and significance
Given these diagnostic limitations and the evolving understanding of glomerular diseases, it is crucial to evaluate the role of EM in improving diagnostic precision. A detailed understanding of the histopathological spectrum across all three modalities – LM, IF, and EM – can enhance diagnostic accuracy, reduce misclassification, and inform appropriate management. This is particularly relevant in a resource-limited setting like India, where judicious use of advanced diagnostics must be balanced against cost-effectiveness. Assessing the incremental value of EM can provide important insights into when and how it should be deployed in routine clinical practice.
Study objective
The present study aims to describe the histopathological spectrum of glomerular diseases in both pediatric and adult patients presenting with NS and/or NRP using LM, IF, and EM. In addition, the study seeks to assess the diagnostic value of EM in differentiating glomerular pathologies in this patient population and to determine its utility in cases with inconclusive findings on LM and IF.
MATERIALS & METHODS
This prospective observational study was conducted at Sir Ganga Ram Hospital, a tertiary care center in New Delhi, India, over 1.5 years (from January 2019 to June 2020). The study protocol was reviewed and approved by the Institutional Ethics Committee (IEC) of Sir Ganga Ram Hospital (Approval Number: EC/01/19/1480). As this was a retrospective analysis of diagnostic biopsy samples with no direct patient intervention, the requirement for informed consent was waived by the institutional review board.
Kidney biopsies obtained from pediatric (<18 years) and adult (≥18 years) patients presenting with NS (characterized by hypoalbuminemia [plasma albumin levels <3 g/dL for adults and <2.5 g/dL for pediatric patients], hyperlipidemia [serum cholesterol >200 mg/dL], and generalized edema]) and NRP (early morning urine protein of 3+/4+ [on dipstick or boiling test], urine spot protein/creatinine ratio >2, or urine albumin excretion >40 mg/m2/h [on a timed-sample] for pediatric patients and >3.5 g/24 h/1.73 m2 in adults) were evaluated.
Inclusion and exclusion criteria
Study population
The study included biopsy-proven glomerular diseases in both pediatric patients (under 18 years of age) and adults (18 years and older) who presented with new-onset NS or NRP. Patients were excluded if they had known secondary causes of proteinuria, such as malignancy, chronic infections (including HIV, hepatitis B, or hepatitis C), or autoimmune diseases other than lupus nephritis, unless a renal biopsy was indicated to investigate the possibility of coexisting glomerular disease. Cases of established diabetic nephropathy were also excluded, except when atypical clinical or pathological features warranted a biopsy. In addition, patients undergoing repeat or follow-up biopsies – such as those related to disease relapse or treatment monitoring – were excluded to ensure a uniform cohort of newly diagnosed cases.
Sample preparation (biopsy procedure)
Three core biopsy specimens were obtained under ultrasound guidance using the Bard® Max-Core® Disposable Core biopsy instrument (18G × 16 cm) for all patients, with one core each designated for LM, direct IF, and EM. A minimum of 8 glomeruli per linear core for LM, 3 for IF, and 1 for EM was considered adequate for evaluation.
Light microscopy
The core designated for LM was fixed in 10% neutral-buffered formalin, processed routinely, and embedded in paraffin. Sections of 3–4 μm thickness were stained with Hematoxylin and Eosin, periodic acid–Schiff, and silver methenamine (Jones’ stain) in all cases, while Congo Red and Masson’s Trichrome were used wherever indicated based on the clinical suspicion. Histopathological assessment was conducted using standard morphological criteria and disease-specific classification systems, such as the Oxford classification for IgA nephropathy (IgAN) and the ISN/RPS classification for lupus nephritis, in accordance with established renal pathology protocols and published literature.
Direct IF staining
The biopsy core for IF was snap-frozen without fixation, and cryostat sections of 3–5 μm were cut and incubated with commercially available fluorescein isothiocyanateconjugated polyclonal rabbit anti-human antibodies against immunoglobulin (Ig)G, IgA, IgM, C3, C1q, kappa, and lambda (Dako, Denmark), following the manufacturer’s protocol. The pattern (granular, linear, etc.), location (mesangial, capillary wall, etc.), and intensity of immune deposits were recorded for each case. The intensity was graded semi-quantitatively on a scale from 0 to 3+, where 0 indicated no fluorescence, 1+ weak, 2+ moderate, and 3+ strong fluorescence. To ensure validity and reproducibility, each run included positive controls comprising renal tissue with known immunoreactivity for the target antigens, and negative controls in which the primary antibody was omitted to detect any background or nonspecific staining. The IF analysis was performed in accordance with standard procedures commonly used in renal pathology laboratories.
Immunohistochemical staining
Anti-amyloid A antibody, monoclonal, clone mc1 (Dako, Santa Clara, CA); Anti-Collagen-III antibody, monoclonal, clone HWD1.1 (BioGenex, Fremont, CA); was done on additional sections prepared from a formalin-fixed, paraffin-embedded block, wherever required. Immunohistochemistry staining was done on the Leica Bond Max immunostainer automated staining instrument.
Electron microscopic staining
Cubes with dimensions of 1 mm were extracted from the biopsy sample ends, followed by dehydration using graded alcohols and embedding in epoxy resin. Semi-thin/survey sections of 0.5–1 μm size were cut with an ultramicrotome and stained with toluidine blue and examined with a light microscope. Thin sections of 70–90 nm were placed onto copper grids coated with carbon and then stained with 2% uranyl acetate for 5 min, followed by staining with lead citrate for 3 min, and were examined in a JEOL Transmission Electron Microscope (JEOL, Tokyo, Japan).
Histomorphological evaluation
The renal biopsies were analyzed with respect to primary changes such as glomerular morphology and secondary changes such as tubulointerstitial lesions and vascular changes. All the biopsies were reported as per the Renal Pathology Society Consensus guidelines 2016.
In line with recent updates in glomerular disease classification, newly recognized or emerging entities were considered during histopathological assessment. These include conditions such as C1q nephropathy, lupus podocytopathy, and collapsing glomerulopathy, among others. Where applicable, these diagnoses were evaluated in conjunction with EM and clinical correlation.
A schematic representation was used to outline the stepwise allocation of biopsy tissue for diagnostic purposes [Figure 1]. The diagram illustrates how the obtained tissue sample was systematically divided for LM, IF, and EM. This approach was employed to enhance clarity in diagnostic workflow planning and ensure optimal utilization of the biopsy material for comprehensive evaluation.
- Schematic representation of biopsy tissue allocation. The diagram illustrates the stepwise division of tissue samples for LM, IF, and EM, enhancing clarity in diagnostic workflow planning. LM: Light microscopy, IF: Immunofluorescence, EM: Electron microscopy.
Statistical analysis
Data were analyzed using Statistical Package for the Social Sciences version 20.0 (IBM Corp., Armonk, NY, USA). Continuous variables were expressed as mean ± standard deviation, and categorical variables were summarized as frequencies and percentages. Normality of continuous variables was assessed using the Shapiro–Wilk test. Comparisons between pediatric and adult groups, and between NS and NRP subgroups, were performed using the Chi-square test or Fisher’s exact test, as appropriate for categorical variables, and the Independent samples t-test or Mann–Whitney U-test for continuous variables. A P < 0.05 was considered statistically significant. For major proportions, 95% confidence intervals (CIs) were calculated.
RESULTS
Demographic and clinical details
A total of 180 cases, involving 36 pediatric and 144 adult patients, were included in the study. The relevant clinical and demographic details are shown in Table 1. The mean age of pediatric patients was 10.58 ± 4.92 years, while adults had a mean age of 45.90 ± 14.03 years. There was a male preponderance in both the age groups (Male: Female ratio of pediatric group – 2:1, adult group – 1.4:1). Most of the pediatric patients presented with NS, while most of the adult patients presented with NRP. NS was the predominant presentation in pediatric patients (72.2%; 95% CI: 55.8– 84.9) compared with adults (47.2%; 95% CI: 38.9–55.5) (P = 0.012). Most of the adults presented with NRP (52.8%; 95% CI: 44.4–61.0).
| Clinical feature/Parameter | Pediatric (n=36) | Adult (n=144) | 95% CI (Pediatric) | 95% CI (Adult) | P-value |
|---|---|---|---|---|---|
| NS | 26 (72.2%) | 68 (47.2%) | 56.8–83.4 | 39.8–54.6 | 0.018 |
| NRP | 10 (27.8%) | 76 (52.8%) | 16.6–43.2 | 45.4–60.2 | 0.018 |
| Mean age (years) | 10.58±4.92 | 45.90±14.03 | 8.92–12.24 | 43.59–48.21 | <0.000001 |
| Hypertension | 7 (19.4%) | 55 (38.2%) | 9.8–34.7 | 30.8–46.2 | 0.049 |
| Hematuria | 14 (38.9%) | 46 (31.2%) | 25.9–54.1 | 24.9–39.8 | NS (0.477) |
| Diabetes mellitus | 0 | 21 (14.6%) | 0.0–9.6 | 9.6–21.6 | 0.0026 |
| 24h proteinuria | 4.75 (3.5–45.2) | 5.48 (3.5–49) | — | — | — |
| Serum creatinine (mg/dL) | 1.14±0.96 | 2.61±2.49 | 0.82–1.46 | 2.20–3.02 | 9.6×10−8 |
NS: Nephrotic syndrome, NRP: Non-nephrotic proteinuria, CI: Confidence interval, 24-h: 24-hour, mg/dL: Milligrams per deciliter
LM and IF examination
Renal biopsy diagnosis in NS patients based on LM/IF
In our study, the renal biopsy diagnoses based on LM and IF revealed that the Focal Segmental Glomerulosclerosis (FSGS) was the most prevalent glomerular disease overall, accounting for 25%. This was followed by IgAN at 12.2% and membranous nephropathy (MN) at 10.6%. Among pediatric NS patients, minimal change nephropathy (MCN) was the most prevalent (38.5%), followed by FSGS at 19.23%. In pediatric NRP cases, MCN remained the leading cause (27.7%), followed by lupus nephritis (22.3%) and FSGS (16.6%). Among adult patients, FSGS was the most common, representing 27.08% of cases, followed by IgAN at 13.19%, MN at 11.8%, and amyloidosis also at 11.8%. The overall spectrum of glomerular diseases in NRP cases on LM/IF is shown in Table 2.
| Diagnosis | Pediatric (n=36) (%) | Adult (n=144) (%) | 95% CI (Pediatric) | 95% CI (Adult) | P-value |
|---|---|---|---|---|---|
| Amyloidosis | 0 | 17 (11.8) | 0.0–9.6 | 7.5–18.1 | 0.026 |
| C3GP | 1 (2.8) | 4 (2.8) | 0.5–14.2 | 1.1–6.9 | NS (1.000) |
| Diabetic nephropathy | 0 | 15 (10.4) | 0.0–9.6 | 6.4–16.5 | 0.044 |
| Diffuse mesangial sclerosis | 2 (5.6) | 0 | 1.5–18.1 | 0.0–2.6 | 0.039 |
| FSGS | 6 (16.7) | 39 (27.1) | 7.9–31.9 | 20.5–34.9 | NS (0.282) |
| IgAN | 3 (8.3) | 19 (13.2) | 2.9–21.8 | 8.6–19.7 | NS (0.574) |
| Immune complex MPGN | 0 | 3 (2.1) | 0.0–9.6 | 0.7–5.9 | NS (1.000) |
| Lupus nephritis (total) | 8 (22.2) | 7 (4.8) | 11.7–38.1 | 2.4–9.7 | 0.0028 |
| Class I | 1 (2.8) | 0 | 0.5–14.2 | 0.0–2.6 | — |
| Class II | 1 (2.8) | 0 | 0.5–14.2 | 0.0–2.6 | — |
| Class III | 2 (5.6) | 2 (1.4) | 1.5–18.1 | 0.4–4.9 | — |
| Class III+V | 1 (2.8) | 0 | 0.5–14.2 | 0.0–2.6 | — |
| Class IV | 3 (8.3) | 5 (3.4) | 2.9–21.8 | 1.5–7.7 | — |
| MCN | 10 (27.8) | 8 (5.6) | 15.8–43.9 | 2.8–10.6 | 0.00043 |
| MN | 2 (5.6) | 17 (11.8) | 1.5–18.1 | 7.5–18.1 | NS (0.373) |
| MSGN | 0 | 3 (2.1) | 0.0–9.6 | 0.7–5.9 | NS (1.000) |
| Collagenofibrotic disease | 0 | 1 (0.7) | 0.0–9.6 | 0.1–3.8 | NS (1.000) |
| PICGN | 2 (5.6) | 9 (6.2) | 1.5–18.1 | 3.3–11.5 | NS (1.000) |
| PSGN | 2 (5.6) | 2 (1.4) | 1.5–18.1 | 0.4–4.9 | NS (0.179) |
C3GP: C3 glomerulopathy, FSGS: Focal segmental glomerulosclerosis, IgAN: IgA nephropathy, MPGN: Membranoproliferative glomerulonephritis, MCN: Minimal change nephropathy, MN: Membranous nephropathy, MSGN: Mesangioproliferative glomerulonephritis, PICGN: Pauci-immune crescentic glomerulonephritis, PSGN: Post-streptococcal glomerulonephritis, CI: Confidence interval, NS: Not significant
Tubulointerstitial and blood vessel changes
Within the tubular compartment, tubular atrophy was observed in 102 cases, representing 56.7%, predominantly of a mild degree. Acute tubular injury was identified in 25 patients, constituting 13.9%, with 2 cases in the pediatric group and 23 in the adult population. Lymphocytic infiltration in the interstitial space was observed in 120 cases, constituting 66.7%, whereas interstitial fibrosis was present in 50 cases, accounting for 27.8%. Vascular alterations were observed in 66 cases, with 43 exhibiting arteriosclerosis, 6 displaying hyalinosis, and 17 showing amyloid deposition within the vessel walls.
Electron microscopic examination
In the present study, podocyte effacement was observed in all 180 cases. Conditions such as FSGS, MCN, and diffuse mesangial sclerosis often exhibited extensive podocyte effacement. Microvillous (MV) transformation was identified in 53 cases, constituting 29.5% of the study cohort. The leading glomerular disease displaying MV transformation was FSGS, accounting for 54.7%. This was subsequently followed by MN at 18.9%, with both MCN and lupus nephritis each accounting for 13.2%. In our present investigation, 93.3% of lupus nephritis cases (14 out of 15) exhibited the presence of TRI. In addition, TRI were observed in 13.9% (6 cases) of FSGS.
In this study, the effectiveness of EM in diagnosing glomerular diseases was evaluated by classifying the data into three categories [Table 3 and Figure 2a-f]. First, the cases where EM played a crucial role in making the diagnosis, indicating that an accurate diagnosis would not have been possible without ultrastructural examination, were categorized as Category I. The Category II included those instances where EM provided supportive or helpful information in the diagnosis, offering additional data that confirmed the diagnosis, ruled out differential diagnoses, or supplied therapeutically or prognostically relevant details. Finally, the third category (Category III) included cases where EM findings were consistent with those observed through LM and IF, suggesting no substantial contribution to establishing the diagnosis. On analysis, EM was found to be contributory (including both Category I and II) in 53 cases (29.45%). Of this percentage, it was indispensable (Category I) for diagnosis in 22 cases (12.2%) and provided valuable assistance (Category II) in an additional 31 cases (17.2%). Details of cases belonging to Category I and Category II are shown in Table 4.
| EM contribution | Pediatric (n=36) (%) | Adult (n=144) (%) | 95% CI (Pediatric) | 95% CI (Adult) | P-value |
|---|---|---|---|---|---|
| Category I (Essential) | 10 (27.8) | 12 (8.3) | 15.8–43.9 | 4.8–14.1 | 0.0009 |
| Category II (Helpful) | 3 (8.3) | 28 (19.5) | 2.9–21.4 | 13.8–26.7 | NS (0.108) |
| Category III (Concordant/Noncontributory) | 23 (63.9) | 104 (72.2) | 47.8–77.6 | 64.8–78.4 | NS (0.395) |
EM: Electron microscopy, CI: Confidence interval, NS: Not significant
- Electron microscopic images (a) Diffuse and widespread effacement of podocyte process (Uranyl acetate lead citrate ×1500); (b) Highly osmophilic band like electron-dense deposits in lamina densa of glomerular basement membrane (GBM) (Uranyl acetate lead citrate ×2000); (c) high power view showing splitting of lamina densa with “basket” weave” appearance of GBM (Uranyl acetate lead citrate ×4000); (d) Subepithelial electron dense deposits (Uranyl acetate lead citrate ×2500); (e) Amyloid fibrils within mesangium and glomerular capillary wall (arrows) (Uranyl acetate lead citrate ×1000); (f) Higher magnification showing non-branching fibrils 7–10 nm diameter (Uranyl acetate lead citrate ×8000).
| LM/IF diagnosis | No. of Cases | EM findings | EM diagnosis |
|---|---|---|---|
| Category I | |||
| MCN | 17 | Diffuse podocytopathy, No EDD [Figure 2a] | MCN |
| MSGN | 1 | Diffuse podocyte foot process effacement with mesangial EDD | Lupus podocytopathy |
| C3GP | 1 | Highly osmophilic band like EDD in lamina densa of GBM [Figure 2b] | DDD |
| FSGS | 1 | Diffuse podocyte foot process effacement, electron lucent zones, crisscross arrays and “basket” weave” appearance of GBM [Figure 2c] | Alport’s disease |
| MCN | 1 | GBM thickening, subepithelial EDD [Figure 2d] | MN Stage II |
| FSGS | 1 | Mesangial and subendothelial fibrillary deposits (diameter~10.2 nm) [Figure 2e and f]) | Amyloidosis |
| Category II | |||
| MN | 19 | Subepithelial EDD with extension of basement membrane material in between the EDD | MN Stage II |
| C3GP | 4 | Amorphous homogenous EDD in the mesangium, subendothelial and intramembranous location | C3GN |
| FSGS | 3 | Focal effacement of podocyte foot processes | Secondary FSGS |
| IgAN | 3 | Subendothelial EDD in addition to mesangial and paramesangial EDD | IgAN disease, prognosis) |
| Lupus Class IV | 1 | Nephritis | Subepithelial EDD in addition to mesangial and subendothelial EDD |
| Noduloglomerulosclerosis (Collagenofibotic disease) | 1 | Electron dense curvilinear banded fibrils (periodicity~60nm) | Collagenofibrotic disease (confirmed) |
LM: Light microscopy, IF: Immunofluorescence, EM: Electron microscopy, MCN: Minimal change nephropathy, MSGN: Mesangioproliferative glomerulonephritis, C3GP: C3 glomerulopathy, DDD: Dense deposit disease, FSGS: Focal segmental glomerulosclerosis, GBM: Glomerular basement membrane, MN: Membranous nephropathy, EDD: Electron-dense deposits, IgAN: IgA nephropathy
DISCUSSION
This study examined the histopathological spectrum of glomerular diseases in both pediatric and adult patients presenting with NS or NRP. In our cohort of 180 biopsy-proven cases, minimal change disease (MCN) was the most common diagnosis among pediatric NS patients (38.5%), followed by FSGS (19.2%). In adults, FSGS emerged as the leading cause of renal dysfunction, followed by IgAN, amyloidosis, and diabetic nephropathy. Type 2 diabetes mellitus was present in 14.6% of adults, with non-diabetic kidney disease seen in 28.5% of these cases. Notably, 68.75% of adult patients exhibited renal dysfunction (serum creatinine >1.3 mg/dL), with FSGS being the most frequently associated lesion. EM added diagnostic value, particularly in conditions such as MCN, MN, amyloidosis, and lupus nephritis. The histopathological spectrum of glomerular diseases causing nephrotic-range proteinuria and nephrotic syndrome includes primary glomerulopathies—such as MN, MCN, FSGS, MPGN, C3 glomerulopathy, and IgA nephropathy—as well as secondary causes including diabetic nephropathy, amyloidosis, and lupus nephritis. This spectrum varies with demographic and geographic factors, with recent studies from multiple regions reporting an increasing prevalence of FSGS in both paediatric and adult populations with nephrotic syndrome.[5-12]
Our findings align with several Indian studies highlighting the increasing prevalence of FSGS. Rathi et al. reported FSGS as the most common cause of renal dysfunction in their cohort, and Suryawanshi et al. similarly noted renal dysfunction more frequently in diabetic nephropathy than in FSGS or IgAN.[9,13] Comparable trends in paediatric populations, including age-related variation between MCN and FSGS, have been documented in multiple Indian cohorts.[14-18] Among children, the predominance of MCN in younger age groups and a rising incidence of FSGS in older children mirrors the observations of Inamdar et al., Chaudhary et al., and Kumar et al. In particular, Kumar et al.’s 11-year study found FSGS (38%) and MCN (32%) as leading causes, with MCN more prevalent in children under 8 years and FSGS in older age groups. Studies from Cuttack and Lucknow further reinforce this regional variability.[19]
Table 5 summarizes findings from studies conducted on pediatric patients in India,[14-16,21,22] Table 6 presents findings from studies on adult patients in India,[9,13,23,24] and Table 7 outlines findings from pediatric patients worldwide, as reported in the literature.[6,7,18,25,26] Internationally, the growing prevalence of FSGS is a consistent theme. Gulati et al. in India, Mubarak et al. in Pakistan, and studies from Nigeria, Turkey, Canada, and the USA all report a similar trend, especially among adolescents and adults. In Nigeria, the frequency of FSGS rose from 31.8% to 43% over 16 years. Canadian and U.S. studies (e.g., Bonilla-Felix et al.) have documented an increase in FSGS post-1990. Golay et al. reported FSGS as the most frequent cause of adult NS in India (24.6%), closely followed by MCN and MN.[20] These patterns support the notion of a global shift in the histopathological profile of NS.
| Author (s) | Kumar et al.[16](%) | Chaudhari et al.[15] (%) | Inamdar et al.[14] (%) | Kanodia et al.[21] (%) | Joshi et al.[22](%) | Present study |
|---|---|---|---|---|---|---|
| Place of study | Uttar Pradesh | Maharashtra | Karnataka | Gujarat | Maharashtra | New Delhi |
| Duration of study (y) | 11 | 15 | 1.5 | 6 | 1 | 1.5 |
| Number of NS cases included | 290 | 70 | 25 | 155 | 22 | 26 |
| Age group (y) | <16 | <12 | <18 | <14 | <18 | <18 |
| C1q nephropathy | -- | -- | -- | 1 (0.65) | -- | -- |
| C3GP | -- | -- | -- | -- | -- | 1 (3.8) |
| DMS | 3 (1) | -- | -- | -- | -- | 2 (7.7) |
| DPGN | -- | -- | -- | 3 (1.94) | -- | -- |
| FSGS | 110 (38) | 16 (22.85) | 6 (24) | 19 (12.26) | -- | 5 (19.3) |
| IgAN | -- | 3 (4.28) | 3 (12) | -- | 5 (22.7) | 1 (3.8) |
| IgMN | -- | 4 (5.71) | 1 (4) | 33 (21.29) | 2 (9) | 0 |
| Lupus nephritis | -- | -- | -- | -- | 4 (15.4) | |
| MCN | 95 (33) | 33 (47.14) | 12 (48) | 19 (12.26) | 3 (13.6) | 10 (38.5) |
| MPGN | 44 (15) | 4 (5.71) | -- | 15 (9.67) | 1 (4.5) | -- |
| MN | 5 (2) | 3 (4.28) | -- | 8 (5.16) | -- | 2 (7.7) |
| MSGN | 33 (11) | 5 (7.14) | 1 (4) | 52 (33.55) | 10 (45.5) | 0 |
| PICGN | -- | -- | -- | -- | -- | 1 (3.8) |
| PSGN | -- | 1 (1.42) | -- | -- | -- | 0 |
| Others | -- | 1 (1.47) | 2 (8) | 5 (3.22) | 1 (4.56) | -- |
NS: Nephrotic syndrome, C3GP: C3 glomerulopathy, DMS: Diffuse mesangial sclerosis, DPGN: Diffuse proliferative glomerulonephritis, FSGS: Focal segmental glomerulosclerosis, IgAN: IgA nephropathy, IgMN: IgM nephropathy, MCN: Minimal change nephropathy, MPGN: Membranoproliferative glomerulonephritis, MN: Membranous nephropathy, MSGN: Mesangioproliferative glomerulonephritis, PICGN: Pauci-immune crescentic glomerulonephritis, PSGN: Post-streptococcal glomerulonephritis
| Author (s) | Golay et al.[20](%) | Krishna et al.[23] (%) | Rathi et al.[9] (%) | Konana et al.[24] (%) | Suryawashi et al.[13] (%) | Present study |
|---|---|---|---|---|---|---|
| Place of study | West Bengal | Bihar | Punjab | Karnataka | Maharashtra | New Delhi |
| Duration of study (y) | 2.5 | 2.5 | 5 | 2.5 | 4 | 1.5 |
| Number of NS cases included | 410 | 228 | 364 | 122 | 209 | 68 |
| Age group (y) | >18 | >18 | 18–60 | >18 | 18–80 | >18 |
| Amyloidosis | 5 (1.22) | 2 (0.88) | 12 (3.3) | -- | 8 (3.52) | 12 (17.6) |
| Diabetic nephropathy | 2 (0.49) | 3 (1.32) | 1 (0.27) | -- | 22 (9.69) | 9 (13.2) |
| DPGN | -- | 33 (14.47) | 9 (2.45) | 4 (3.2) | -- | -- |
| FSGS | 101 (24.63) | 69 (30.26) | 99 (27.2) | 20 (16.3) | 25 (11.01) | 18 (26.5) |
| IgAN | 30 (7.32) | 20 (8.77) | 6 (1.65) | 9 (7.3) | 21 (9.25) | 5 (7.4) |
| Immune complex mediated MPGN | 28 (6.83) | 19 (8.33) | 58 (15.93) | 2 (1.6) | 28 (12.33) | 1 (1.5) |
| Lupus nephritis | 27 (6.58) | 11 (4.83) | 25 (6.87) | 19 (8.38) | 0 | |
| MCN | 98 (23.9) | 13 (5.7) | 48 (13.19) | 49 (40.1) | 36 (15.85) | 7 (10.3) |
| MN | 92 (22.44) | 29 (12.72) | 79 (21.7) | 30 (24.5) | 28 (12.33) | 10 (14.7) |
| MSGN | 1 (0.24) | 7 (3.07) | -- | 5 (4) | 30 (13.21) | 3 (4.4) |
| Collagenofibrotic disease | -- | -- | -- | -- | -- | 1 (1.5) |
| PICGN | 5 (1.22) | 4 (1.75) | -- | -- | -- | 2 (2.9) |
| PSGN | 6 (1.46) | -- | -- | -- | -- | -- |
| Others | 15 (3.65) | 18 (7.89) | 27 (7.4) | 3 (2.4) | 10 (4.43) | -- |
NS: Nephrotic syndrome, DPGN: Diffuse proliferative glomerulonephritis, FSGS: Focal segmental glomerulosclerosis, IgAN: IgA nephropathy, MPGN: Membranoproliferative glomerulonephritis, MCN: Minimal change nephropathy, MN: Membranous nephropathy, MSGN: Mesangioproliferative glomerulonephritis, PICGN: Pauci-immune crescentic glomerulonephritis, PSGN: Post-streptococcal glomerulonephritis
| Author (s) | Filler et al.[7] | Choi et al.[25] | Rychlik et al.[26] | Fidan et al.[6] | Mubarak et al.[18] | Present study | |
|---|---|---|---|---|---|---|---|
| Place of study | Canada | Korea | Czech Republic | Turkey | Pakistan | India | |
| Duration of study (y) | 17 | 23 | 7 | 20 | 13 | 1.5 | |
| Number of NS cases included | 159 | 1430 | 693 | 3892 | 538 | 26 | |
| 365 | 173 | ||||||
| Age group (y) | <18 | <18 | <15 | <18 | <13 | 13–18 | <18 |
| C3GP (%) | -- | -- | -- | -- | -- | 1 (1.2%) | 1 (3.8%) |
| DMS (%) | -- | -- | -- | -- | -- | -- | 2 (7.7%) |
| FSGS (%) | 29 (18.2) | 57 (4) | 8.4 | 641 (16.46) | 143 (39.2) | 63 (36.4) | 5 (19.3) |
| IgAN (%) | -- | 148 (10.3) | 28.6 | 237 (6.08) | 3 (0.8) | 3 (1.7) | 1 (3.8) |
| Lupus nephritis (%) | -- | 28 (2) | -- | 211 (5.42) | -- | -- | 4 (15.4) |
| MCN (%) | 115 (72.3) | 355 (24.8) | 26.2 | 396 (10.17) | 187 (51.2) | 50 (28.9) | 10 (38.5) |
| MPGN (%) | 1 (0.6) | 30 (2.1) | 3 | 317 (8.14) | 4 (1.1) | 13 (7.5) | -- |
| MN (%) | 3 (1.9) | 43 (3) | 1.9 | 61 (1.56) | 11 (3) | 32 (18.5) | 2 (7.7) |
| MSGN (%) | 8 (5) | 38 (2.7) | 11.8 | 400 (10.27) | 17 (4.7) | 9 (5.2) | 0 |
| PICGN (%) | -- | 2 (0.1) | 0.7 | 198 (5.08) | -- | -- | 1 (3.8) |
| PSGN (%) | -- | 123 (8.6) | 1.3 | 188 (4.8) | -- | 1 (0.6) | 0 |
NS: Nephrotic syndrome, C3GP: C3 glomerulopathy, DMS: Diffuse mesangial sclerosis, FSGS: Focal segmental glomerulosclerosis, IgAN: IgA nephropathy, MPGN: Membranoproliferative glomerulonephritis, MCN: Minimal change nephropathy, MN: Membranous nephropathy, MSGN: Mesangioproliferative glomerulonephritis, PICGN: Pauci-immune crescentic glomerulonephritis, PSGN: Post-streptococcal glomerulonephritis
An important observation in our study was the high prevalence of renal dysfunction among adults (68.75%), with FSGS being the predominant lesion in these cases. This is consistent with previous Indian data but is particularly striking in our cohort. In addition, among adult diabetic patients, a significant proportion (28.5%) had non-diabetic kidney diseases, primarily FSGS, indicating the importance of renal biopsy in diabetic patients with atypical presentations. In pediatric patients, the presence of hypertension and hematuria in a subset of those with MCN or FSGS suggests a need for careful clinical correlation beyond typical NS features. In our study, MCN emerged as the most prevalent glomerular disease among pediatric NS patients. This finding aligns with the well-documented predominance of MCN in children but shows a slightly higher proportion compared to some other Indian and international studies.[7,8,14-16]
One possible explanation for this could be the younger age distribution within our pediatric cohort, as MCN is known to be more common in children under 8 years of age. In addition, variability in referral patterns and clinical thresholds for performing a biopsy may influence the diagnostic yield. In some centers, empirical steroid therapy is initiated without biopsy in typical NS cases, whereas in our setting, earlier biopsies may have captured more MCN cases that would otherwise have remained undocumented. Another contributing factor could be genetic or regional susceptibility, although this warrants further investigation.
The high prevalence of FSGS among adult patients in our study is consistent with global trends, which indicate a rising incidence of FSGS as a leading cause of adult NS. However, local risk factors may also play a significant role. In our cohort, a considerable number of patients had hypertension and/or Type 2 diabetes, both of which are associated with secondary forms of FSGS. In addition, lifestyle-related factors such as obesity, which were not systematically assessed in this study, could contribute to this trend. The possibility of genetic predisposition or environmental influences in our population may also explain the increased FSGS burden and should be explored in future studies with a broader epidemiological scope.
EM played a crucial role in confirming and refining diagnoses in our study. It was particularly helpful in identifying podocyte foot process effacement in MCN and FSGS, subepithelial deposits in MN, and amyloid fibrils in suspected amyloidosis. In lupus nephritis, EM was essential for determining the class based on deposit location and identifying tubuloreticular inclusions. Our findings are in line with those of Mokhtar and Jallalah, who reported EM to be essential in 16.5% and contributory in 22.3% of cases. Similarly, Jahanzad et al. and Kurien et al. documented EM’s diagnostic value in over one-third of their cohorts. Despite its value, access to EM remains limited in many regions due to resource constraints, underscoring the need for strategic integration of this tool in nephropathology services in developing countries. Table 8 compares the contribution of electron microscopy across published studies and places the findings of the present study in the context of existing literature.[27-33]
| Author(s) | Pearson et al.[27] | Mokhtar and Jallalah.[28] | Jahanzad et al.*[29] | Collan et al.[30] | Rivera et al.*[31] | Haas[32] | Kurien et al.[33] | Currentstudy |
|---|---|---|---|---|---|---|---|---|
| Place of study | England | Saudi Arabia | Iran | Finland | USA | USA | India, USA | India |
| Duration of study (y) | 1 | 7 | 6 | 1 | 8 | 0.5 | 0.5 | 1.5 |
| Number of cases included | 88 | 273 | 134 | 71 | 48 | 213 | 115 | 180 |
| Essential/Crucial (%) | 25 | 17 | 38 | 18.3 | 73 | 11 | 12 | 12.2 |
| Helpful/Supportive (%) | 50 | 22 | 30 | 53.5 | 27 | 36 | 20 | 17.2 |
| Concordant/Noncontributor y (%) | 25 | 61 | 32 | 28.2 | 0 | 53 | 68 | 70.6 |
Limitations
Our study had few limitations. As the present study was carried out at a single center using a descriptive design, the generalizability of the findings was naturally limited. The unequal distribution of pediatric and adult cases may also have affected the strength of comparisons between the two groups. In addition, most of the analyses were descriptive, and only limited inferential statistical testing could be performed. We were also unable to include follow-up or clinical outcome data, preventing any correlation between histopathological patterns and long-term patient prognosis. Finally, while EM added significant diagnostic value, its limited availability and higher cost in many centers may restrict the broader applicability of our EM-based observations.
CONCLUSION
This study found that in pediatric NS patients, the most frequent glomerular disease was MCN, followed by FSGS. Among adult NS patients, FSGS was the most prevalent, with amyloidosis and MN ranking next. In pediatric patients with NRP, MCN was again the leading cause, followed by lupus nephritis and FSGS. In adult NRP cases, FSGS was the most common diagnosis, followed by IgAN, MN, and amyloidosis. These findings highlight the evolving spectrum of glomerular diseases across age groups and emphasize the value of comprehensive renal biopsy evaluation using LM, IF, and, where feasible, EM. In settings where EM is not routinely available, preserving biopsy material in appropriate fixatives allows for deferred ultrastructural assessment when clinically indicated. By understanding the predominant patterns of glomerular diseases in specific age groups, clinicians can more accurately tailor diagnostic approaches and initiate appropriate treatment strategies earlier. For example, early identification of MCN in children can support prompt corticosteroid initiation, while the recognition of FSGS or amyloidosis in adults may warrant alternative immunosuppressive or supportive therapies. This targeted approach can lead to faster diagnosis, reduced diagnostic delays, and improved disease management.
Authors’ contributions:
Conceptualization was performed by PG, VB, and KA. Data curation was undertaken by SSD and MAO. Project administration was managed by PG. The original draft of the manuscript was written by SSD, MAO and PG. Critical review and editing of the manuscript were carried out by MAO and PG. All authors approved the final version of the manuscript and agree to be accountable for all aspects of the work.
Ethical approval:
The research/study was approved by the Institutional Review Board at Sir GangaRam Hospital, New Delhi, India, number EC/01/19/1480, dated January 2019.
Declaration of patient consent:
Patient’s consent not required as patients identity is not disclosed or compromised.
Conflict of interest:
There are no conflicts of interest.
Availability of data and material:
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
Financial support and sponsorship: Nil.
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