Location of glomerular immune deposits, not codeposition of immunoglobulin G, influences definitive renal outcomes in immunoglobulin A nephropathy

A case of paraneoplastic IgA nephropathy with glomerular capillary IgA and galactose-deficient IgA1 deposition

Paraneoplastic IgA nephropathy (IgAN) is an underrecognized condition in which malignancy manifests as symptoms of IgAN, and it remains controversial regarding their mechanistic relation between IgAN and malignancy. Herein, we report a case of a 68-year-old Japanese man with glottic cancer who developed nephrotic syndrome as a clinical manifestation of IgAN. Renal biopsy revealed diffuse proliferative glomerulonephritis with glomerular capillary IgA deposition that is a rare subtype of IgAN. After complete remission of the glottic cancer by irradiation, proteinuria and hematuria disappeared. Based on his clinical course, we diagnosed paraneoplastic IgAN. Therefore, we should consider the possibility that IgAN with glomerular capillary IgA deposition might be paraneoplastic glomerulopathy especially before initiating immunosuppressive therapy. The patient thereafter developed prostate cancer and hepatocellular cancer, but IgAN did not recur. The association of IgAN specifically with the glottic cancer in this triple-cancer patient may suggest a potential link between IgAN and mucosal cancer. Because galactose-deficient IgA1 (Gd-IgA1) was observed in the similar pattern as IgA, Gd-IgA1 also may play an important role in the pathogenesis of paraneoplastic IgAN.

IgA nephropathy with glomerular capillary IgA deposition following SARS-CoV-2 mRNA vaccination: a report of three cases

IgA nephropathy (IgAN) cases histopathologically showing glomerular capillary IgA deposition represent a rare subtype of primary IgAN. Patients with IgAN categorized to this subtype often exhibit heavy proteinuria, advanced histological findings, and are resistant to therapies. Here, we report three cases of biopsy-proven IgAN with glomerular capillary IgA deposition who presented acute deterioration of urinalysis findings following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccinations. Case 1 was recurrent IgAN. Case 2 and Case 3 were newly diagnosed cases with subclinical microhematuria and proteinuria history. All three cases showed gross hematuria and acute exacerbations of proteinuria following SARS-CoV-2 mRNA vaccinations. In all three cases, kidney biopsy findings showed IgA deposition in glomerular capillary walls in addition to mesangial and para-mesangial areas; acute glomerular lesions, such as intra- and extracapillary proliferations were identified, indicating the possibility of a potentially severe type of IgAN. Therefore, attention should be paid to patients with de novo or relapsing IgAN showing marked capillary IgA deposition following SARS-CoV-2 vaccination.

The relationship between glomerular IgG staining and poor prognostic findings in patients with IgA nephropathy: the data from TSN-GOLD working group

Background

Galactose-deficient IgA1 (Gd-IgA1) has an increased tendency to form immunocomplexes with IgG in the serum, contributing to IgAN pathogenesis by accumulating in the glomerular mesangium. Several studies showed that glomerular IgG deposition in IgAN is an important cause of mesangial proliferation and glomerular damage. This study aims to determine the association of the positivity of IgG and the intensity of IgG staining with a poor renal prognosis.

Methods

A total of 943 IgAN patients were included in the study. Glomerular IgG staining negative and positive patients were compared using Oxford classification scores, histopathological evaluations, proteinuria, eGFR, albumin, blood pressures. IgG positive patients were classified as (+), (++), (+++) based on their staining intensity, and the association with the prognostic criteria was also evaluated.

Results

81% (n = 764) of the patients were detected as IgG negative, while 19% (n = 179) were positive. Age, gender, body mass index, blood pressure, proteinuria, eGFR, uric acid values were similar in IgG positive and negative patients who underwent biopsy (p > 0.05). Intensity of glomerular IgG positivity was not found to be associated with diastolic and systolic blood pressure, urea, uric acid, age, eGFR, albumin, proteinuria (p > 0.05 for all, r = − 0.084, r = − 0.102, r = − 0.006, r = 0.062, r = 0.014, r = − 0.044, r = − 0.061, r = − 0.066, r = 0.150, respectively). There was no difference for histopathological findings between IgG (+), IgG (++), IgG (+++) groups (for all, p > 0.05).

Conclusion

Glomerular IgG negativity and positivity detected by routine IFM in IgAN patients is not associated with poor renal prognostic risk factors.

IgG deposits in the mesangium and capillary loops predict poor renal outcome in patients with IgA nephropathy: a single-center retrospective study

Background

Glomerular IgG deposition in patients with IgA nephropathy (IgAN) has been shown to be associated with poor renal survival; however, most published studies to date are too small-scale and inconsistent to provide guidance for clinical practice.

Methods

Based on renal biopsy findings, 742 patients were divided into the following groups: (i) IgA deposition alone (IgA) vs IgA + IgG deposition (IgA + IgG) and (ii) IgG co-deposition confined to the mesangium vs mesangium + capillary loops (CLs). The clinicopathological variables at biopsy and renal outcome were assessed.

Results

Of the 742 patients, 182 had IgG co-deposition and 51 had IgG deposits in the mesangium + CLs. Patients with IgG co-deposition were associated with severe clinical and pathological lesions, especially those with a location of IgG deposits in the mesangium +CLs. Kaplan–Meier analysis revealed that a lower renal cumulative survival rate was present in both patients with IgG co-deposition and those with a location of IgG deposits in the mesangium + CLs (all p < 0.05). Moreover, patients with a higher intensity of glomerular IgG deposits or C3 deposits or C1q deposits were also associated with a lower survival rate. A multivariate Cox regression model identified the location of IgG deposits in the mesangium + CLs as an independent risk factor for poor prognosis (HR, 2.11; 95% CI: 1.06–4.18; p = 0.005).

Conclusions

Glomerular IgG co-deposition and the location of glomerular IgG deposits in the mesangium + CLs were both associated with adverse renal outcomes, but only the location of glomerular IgG deposits in the CLs was an independent risk factor for poor prognosis in IgAN.

Clinicopathological significance of glomerular capillary IgA deposition in childhood IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is characterized by predominant mesangial IgA deposition. Some patients with IgAN demonstrate IgA deposition in glomerular peripheral capillaries (cap-IgA). The clinicopathological significance of cap-IgA remains incompletely investigated in children.

METHODS

We retrospectively analyzed 503 consecutive cases of biopsy-proven childhood IgAN between July 1976 and June 2013 to compare clinical and pathological features between IgAN patients with and without cap-IgA.

RESULTS

Among the 503 patients, 30 (6.0%) had cap-IgA. We found significant differences in proteinuria (2.0 vs. 0.5 g/day/m², p < 0.0001), time from onset to kidney biopsy (2.2 vs. 8.3 months, p < 0.0001), and rate of proteinuria remission after treatment (23.3% vs. 48.0%, p = 0.007) between both groups. Pathological analysis revealed significant differences in M1 (83.3% vs. 56.0%, p = 0.002), ratio of subendothelial electron dense deposits (EDDs, 58.6% vs. 16.5%, p < 0.0001) and subepithelial EDDs (48.3% vs. 16.5%, p = 0.0001), and glomerular basement membrane (GBM) lysis (58.6% vs. 27.1%, p = 0.0006) between both groups. More than half of cap-IgA patients (17/30, 56.7%), whereas only 26.2% of non-cap-IgA patients (124/473), were treated with immunosuppressive treatments. Six of 30 cases (20%) with cap-IgA reached glomerular filtration rate (GFR) categories G3a-G5 (estimated GFR < 60 ml/min/1.73 m²) at most recent observation (mean observation period: 7.0 ± 4.0 years). According to Kaplan-Meier analysis, patients with cap-IgA had significantly lower kidney survival curves than non-cap-IgA patients (72.8% vs. 97.2% at 10 years, p < 0.0001).

CONCLUSIONS

Cap-IgA is associated with acute inflammation with GBM changes, resulting in refractory heavier proteinuria. Cap-IgA may represent a poor prognostic factor.

Immunofluorescence deposits in the mesangial area and glomerular capillary loops did not affect the prognosis of immunoglobulin a nephropathy except C1q:a single-center retrospective study

Background

Immunoglobulin A nephropathy (IgAN) is identified as mesangial IgA deposition and is usually accompanied by other immunofluorescence deposits. The impact of immunofluorescent features in IgAN patients, however, remains unclear.

Methods

Baseline clinicopathologic parameters and renal outcomes of 337 patients diagnosed with IgAN between January 2009 and December 2015 were analyzed. We then categorized these patients into four groups: without immunofluorescence deposits, mesangial-only, mesangial and glomerular capillary loops (GCLs), and GCLs-only. The study endpoint was end-stage kidney disease (ESKD) or a ≥ 50% decline in the estimated glomerular filtration rate (eGFR). Kaplan–Meier and Cox regression analyses were performed to calculate renal survival.

Results

Of the 337 IgAN patients, women comprised 57.0%. Compared to patients with IgA deposition in the mesangial-only group, patients with IgA deposition in the mesangial +GCLs group were much heavier, and exhibited higher systolic blood pressure, lower serum IgG levels, and heavier proteinuria (all P < 0.05). Patients with IgG deposition in the mesangial +GCLs group presented with higher levels of cholesterol, heavier proteinuria than IgG deposition in the mesangial-only group (both P < 0.05). Compared with the mesangial-only group exhibiting C3 deposits, patients in the mesangial +GCLs group with C3 deposition had a higher systolic blood pressure (P = 0.028). A total of 38 patients (11.3%) continued to the study endpoint after a median follow-up time of 63.5 months (range,49.8–81.4). Kaplan–Meier analysis and Cox regression analysis showed that C1q deposition in the mesangial +GCLs group predicted a poor renal prognosis.

Conclusions

IgA and IgG deposits in the mesangial region and GCLs were associated with more unfavorable clinical and histopathologic findings in IgAN patients. C1q deposition in the mesangial region and GCLs predicted a poor renal prognosis. However, the impact of the pattern of immunofluorescence deposits on renal outcomes remains to be proven by further investigation.

Has The Time Arrived to Refine The Indications of Immunosuppressive Therapy and Prognosis in IgA Nephropathy?

Immunoglobulin A nephropathy (IgAN) is the most frequent glomerular disease worldwide and a leading cause of end-stage renal disease. Particularly challenging to the clinician is the early identification of patients at high risk of progression, an estimation of the decline in renal function, and the selection of only those that would benefit from additional immunosuppressive therapies. Nevertheless, the pathway to a better prognostication and to the development of targeted therapies in IgAN has been paved by recent understanding of the genetic and molecular basis of this disease. Merging the data from the Oxford Classification validation studies and prospective treatment studies has suggested that a disease-stratifying algorithm would be appropriate for disease management, although it awaits validation in a prospective setting. The emergence of potential noninvasive biomarkers may assist traditional markers (proteinuria, hematuria) in monitoring disease activity and treatment response. The recent landmark trials of IgAN treatment (STOP-IgAN and TESTING trials) have suggested that the risks associated with immunosuppressive therapy outweigh the benefits, which may shift the treatment paradigm of this disease. While awaiting the approval of the first therapies for IgAN, more targeted and less toxic immunotherapies are warranted. Accordingly, the targeting of complement activation, the modulation of mucosal immunity, the antagonism of B-cell activating factors, and proteasomal inhibition are currently being evaluated in pilot studies for IgAN treatment.

Aberrant Glycosylation of the IgA1 Molecule in IgA Nephropathy

IgA nephropathy, the most common primary glomerulonephritis in the world and a frequent cause of end-stage renal disease, is characterized by typical mesangial deposits of IgA1, as described by Berger and Hinglaise in 1968. Since then, it has been discovered that aberrant IgA1 O-glycosylation is involved in disease pathogenesis. Progress in glycomic, genomic, clinical, analytical, and biochemical studies has shown autoimmune features of IgA nephropathy. The autoimmune character of the disease is explained by a multihit pathogenesis model, wherein overproduction of aberrantly glycosylated IgA1, galactose-deficient in some O-glycans, by IgA1-secreting cells leads to increased levels of circulatory galactose-deficient IgA1. These glycoforms induce production of autoantibodies that subsequently bind hinge-region of galactose-deficient IgA1 molecules, resulting in the formation of nephritogenic immune complexes. Some of these complexes deposit in the kidney, activate mesangial cells, and incite glomerular injury. Thus, galactose-deficient IgA1 is central to the disease process. In this article, we review studies concerning IgA1 O-glycosylation that have contributed to the current understanding of the role of IgA1 in the pathogenesis of IgA nephropathy.

Corticosteroid therapy in IgA nephropathy with minimal proteinuria and high renal pathological score: A single‑center cohort study

Currently, there is no clear evidence that advocates the widespread use of corticosteroids for the treatment of immunoglobulin A nephropathy (IgAN) with minimal proteinuria (<1 g/day). The recent Kidney Disease: Improving Global Outcomes Clinical Practice Guideline recommends supportive corticosteroid treatment. In the present study, 45 IgAN patients with high renal pathological scores and minimal proteinuria were enrolled. The patients were randomly divided into two groups. The treatment group received methylprednisolone tablets in addition to angiotensin‑converting‑enzyme inhibitor (ACE‑I) and/or angiotensin‑receptor blocker (ARB) treatment. The control group only received ACE‑I and/or ARB treatment. In the treatment group, a single dose of 1 mg/kg (maximum 60 mg/day) methylprednisolone tablets was given daily followed by gradually decreasing dosage. The follow‑up time of the patients was 3 years. In addition, the underlying mechanisms were investigated. The results indicated that there was a significant reduction in the amount of urinary proteins in the treatment group compared with the control group. At the end of the follow‑up, the endpoint event rate of moderate or severe proteinuria and decrease in estimated glomerular filtration rate (eGFR) in the treatment group was significantly lower than the control group. Furthermore, higher levels of serum cytokines, interleukin (IL)‑4, IL‑17, transforming growth factor‑β1 and IL‑21, were detected in patients with IgAN compared with a group of healthy controls. There was no significant difference in IFN‑γ expression between the IgAN and healthy control groups. Furthermore, the expression of Janus kinase (Jak)1, Jak3, signal transducer and activator of transcription (STAT)3 and STAT6 was significantly upregulated in patients with IgAN compared with healthy controls. However, the expression levels of STAT5 and chaperone protein, C1GALT1 specific chaperone 1, in IgAN patients were significantly reduced compared with healthy controls. In addition, there was no significant difference in the expression of Jak2, tyrosine kinase 2, STAT1 and STAT4 between the two groups. In conclusion, for IgAN patients with minimal proteinuria and high renal pathological score corticosteroid therapy is likely to be effective. The dysregulation of serum cytokine levels in these patients with IgAN may have a role in the pathogenesis and progression of disease, which is associated with the activation of the JAK/STAT signaling pathway.