Phospholipase A2 Receptor Staining Research Articles

Clinicopathological characteristics and outcomes of PLA2R related idiopathic membranous nephropathy in patients with seronegative PLA2R antibodies

Background Idiopathic membranous nephropathy (IMN) with deposits of phospholipase A2 receptor (PLA2R) antigen in glomerular tissue (GAg+) but no circulating serum PLA2R antibody (SAb−) has been reported. However, little is known about the clinicopathological characteristics and prognosis of this subtype. Methods A total of 74 IMN patients with GAg + identified by kidney biopsy were enrolled in this study. We categorized patients into two groups based on the presence or absence of serum PLA2R antibody. Data on clinical features, pathological features, and outcomes were collected. Kaplan–Meier analysis of complete remission (CR) and partial remission (PR) comparing SAb−/GAg + and SAb+/GAg + patients. Cox proportional hazards models was used to examine factors associated with CR and PR. Results Among 74 IMN patients, 14 were SAb−/GAg+. Compared with SAb+/GAg + patients, SAb−/GAg + patients presented with higher levels of albumin, lower levels of cholesterol and low density lipoprotein cholesterol (all p < .01), but similar pathological manifestations of kidney biopsy. Multivariate logistic analyses indicated that low albumin (0.79 [95%CI: 0.66–0.95], p = .01) and high cholesterol (1.81 [95%CI: 1.02–3.19], p = .04) were correlated with seropositivity of PLA2R antibody. SAb−/GAg + patients exhibited a significantly higher probability of CR (p = .03) than patients who were SAb+/GAg+. However, no difference was found in the PR rate. Cox regression analyses showed that compared to SAb+/GAg + patients, SAb−/GAg + was more predictive of complete remission (4.28 [95%CI: 1.01–18.17], p = .04). Conclusion IMN with PLA2R staining on kidney biopsy but without serum PLA2R antibody has milder clinical manifestations and a better prognosis.

IgG4-Related Disease with IgG1-Dominant Membranous Nephropathy: A Rare Case Report

ABSTRACT Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory disorder affecting various organs and tissues. Kidney involvement in IgG4-RD commonly manifests as IgG4-related tubulointerstitial nephritis or IgG4-related membranous nephropathy, with the latter occurring less frequently. The identification of the phospholipase A2 receptor (PLA2R) antigen has improved our understanding of primary membranous nephropathy. Here, we present the case of a 60-year-old Chinese man initially diagnosed with IgG4-related pancreatitis, who achieved clinical remission with glucocorticoid therapy followed by low-dose glucocorticoid maintenance therapy. Two years later, the patient developed nephrotic syndrome. A kidney biopsy revealed membranous nephropathy characterized by glomerular subepithelial deposition of IgG1 and positive PLA2R staining. Rituximab (RTX) treatment resulted in complete clinical remission of nephrotic syndrome, and no recurrence was observed during the 24-month follow-up period. IgG4-RD complicated by membranous nephropathy is a rare pathological feature characterized by glomerular subepithelial IgG1 deposition and positive PLA2R antigen staining. In the present case, RTX treatment was effective in achieving clinical remission. These findings contribute to the evolving understanding of the relationship between IgG4-RD and membranous nephropathy.

Malignancy-associated membranous nephropathy: focus on diagnosis and treatment.

The clinicopathological features of malignancy-associated membranous nephropathy have been described previously, but information about diagnosis and treatment remains limited. Patients with malignancy-associated membranous nephropathy in a tertiary hospital in China between June 2012 and October 2021 were retrospectively reviewed. Forty-two patients with malignancy-associated membranous nephropathy were identified. Compared to patients with idiopathic membranous nephropathy, patients with malignancy-associated membranous nephropathy were older and less frequently showed glomerular phospholipase A2 receptor staining (37.9% vs 85.0%) and IgG4 predominant deposition (66.7% vs 95.0%). At diagnosis of membranous nephropathy, themalignancy was unknown in 67% (28/42) of patients and was detected only by tumor screening. Among the 19 patients with concurrent diagnosis of cancer and biopsy-proven membranous nephropathy, 15 received anticancer treatment alone initially. Six of the 10 patients who attained cancer remission achieved remission of membranous nephropathy, while none of the 5 patients without remission of cancer did, suggesting a causal relationship between the two diseases. Some patients with persistent or relapsing membranous nephropathy following cancerremissionachieved remission of membranous nephropathy after immunosuppressive therapy. Over a median follow-up of 24months, 25% (10/40) of patients died, mainly due to neoplasia. Tumor screening is important in patients with membranous nephropathy, especially in elderly patients and patients with negative phospholipase A2 receptor or non-IgG4 predominant deposition. Remission of membranous nephropathy can be observed following remission of cancer in some cases. Immunosuppressive therapy may be considered if membranous nephropathy does not remit after remission of cancer.

The Sensitivity and Specificity of Serum Phospholipase A2 Receptor Antibodies in Diagnosing Primary Membranous Nephropathy in Patients with Adult Nephrotic Syndrome and its Correlation with Serum Phospholipase A2 Receptor Staining in Kidney Biopsies

Membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome (NS) in nondiabetic adults, with about 70%–80% of cases of MN being primary MN (pMN). Many studies have shown that serum phospholipase A2 receptor (PLA2R) antibodies are a diagnostic and prognostic biomarker for pMN, with a pooled diagnostic sensitivity and specificity of 54%–82% and 89%–100%, respectively, resulting in PLA2R staining and serum PLA2R antibodies being incorporated in the management algorithms of MN. We studied the sensitivity and specificity of serum PLA2R antibodies for diagnosing pMN and its correlation with PLA2R staining in kidney biopsies in a prospective observational study of 58 adult NS subjects undergoing a kidney biopsy. Serum PLA2R antibodies were determined by indirect immunofluorescence (IF) before the biopsy. Kidney biopsies were sent for light microscopy and IF examinations. Biopsy samples with MN histology were stained for PLA2R antigens. Out of the 58 adult NS subjects, 28 were diagnosed with pMN and one with secondary MN. Serum PLA2R antibodies were positive in 12 subjects with pMN, and one had focal segmental glomerulosclerosis not otherwise specified, giving a sensitivity of 42.8% and specificity of 96.7% for diagnosing pMN. There was a significant association between glomerular staining for PLA2R (24 of 28 subjects) and a diagnosis of pMN by kidney biopsy, with a sensitivity of 82.8%. Cohen's kappa agreement between glomerular staining for PLA2R and a diagnosis of MN was 0.83 (0.57–1.08).

Utility of serum anti-phospholipase A2 receptor antibody as a biomarker in membranous nephropathy: An experience from a tertiary care center of Eastern India

Membranous nephropathy (MN) is a pattern of glomerular injury. Exact categorization into primary membranous nephropathy (PMN) or secondary membranous nephropathy (SMN) is essential for treatment. An endogenous podocyte antigen, M-type phospholipase A2 receptor (PLA2R) has been discovered to be involved in the pathogenesis of PMN. In this article, we aimed to analyze renal tissue PLA2R and serum anti-PLA2R antibodies in MN cases and determined the diagnostic utility. The study was of prospective type carried out from March 2019 to August 2020. Analysis of cases of MN was performed with PLA2R paraffin immunoflourescence and serum anti-PLA2R antibody ELISA. Overall sensitivity, specificity, PPV, and NPV of serum anti-PLA2R ELISA for PMN was 91.3%, 80%, 75%, and 93.3%, respectively, and of tissue PLA2R staining for PMN was 91.67%, 81.08%, 75.86%, and 93.75%, respectively. There was strong concordance between two methods. In the patients that were followed up, we found baseline serum anti-PLA2R antibody was less in complete remission group than that in non-remission group and the reduction in serum anti-PLA2R antibody was more in complete remission group than that in non-remission group. Routine light and immunofluorescence examination are incapable of giving exact categorical opinion regarding PMN and SMN. Serum anti-PLA2R antibody detection and renal tissue PLA2R analysis are sensitive and specific in detecting PMN. Baseline serum anti-PLA2R antibody and anti-PLA2R antibody quantification trends are related to prognosis of PMN. So they can be incorporated as additional biomarker.

Clinical Evaluation of Antiphospholipase A2 Receptor IgG4 level and Its IgG4-to-IgG Ratio Based on Quantitative Immunoassays in Idiopathic Membranous Nephropathy.

Background Phospholipase A2 receptor (PLA2R), located at the membrane of glomerular podocyte, is the major autoantigen of idiopathic membranous nephropathy (IMN), and its antibodies with a predominant IgG4 subclass lead to pathological lesions. Further studies could be performed to validate the clinical values of PLA2R-IgG, PLA2R-IgG4, and PLA2R-IgG4-to-IgG ratios, as ultrasensitive and quantitative immunoassays for PLA2R antibodies have been well established in our previous work. Methods A cohort of 58 IMN patients, 30 of whom were followed from 3 to 42 months, was assessed for serum PLA2R-IgG and -IgG4 levels, and the ratio of PLA2R-IgG4/-IgG combined with relative clinicopathological indicators. Results Serum PLA2R-IgG4 level was significantly correlated with glomerular PLA2R staining. In addition, it was strongly correlated with PLA2R-IgG and its ratio. PLA2R-IgG and -IgG4 levels were both correlated with high-density lipoprotein and erythrocyte sedimentation rates. The ratio at the first diagnosis can predict the remission, and its efficacy overmatched PLA2R-IgG4. In the survival curves, negative results for the ratio or PLA2R-IgG4 at the first diagnosis demonstrated higher remission rates. Conclusion Serum PLA2R-IgG4 concentration may replace renal PLA2R immunohistochemistry in IMN diagnosis. We propose that the PLA2R-IgG4-to-IgG ratio and PLA2R-IgG4 could be novel indicators for remission prediction in clinical practice.

A Case of Membranous Nephropathy Hypothesized to be Associated With COVID-19 Vaccine

A 56-year-old male patient with a medical history of essential hypertension was referred to the emergency room after he was found to have a serum creatinine level of 13 mg/dL at his primary care physician’s office. The patient reported that he had developed a coronavirus disease 2019 (COVID-19)-like infection six months prior that was not confirmed. Two months later, he started to notice dyspnea on exertion and bilateral lower limb swelling and was started on furosemide. He received the first dose of the Moderna COVID-19 vaccine a month before the presentation but did not receive the second dose. Subsequently, his lower limb swelling and exertional dyspnea started worsening. He denied any new medication, dysuria, oliguria, hematuria, fever, or any other symptoms. Initial evaluation was consistent with kidney failure. Hypocalcemia and hyperphosphatemia were noted, along with medical renal disease on renal ultrasound. Eosinophils and nephrotic-range proteinuria were found in the urine. His serum phospholipase A2 receptor (PLA2R) antibodies were positive. A renal biopsy showed membranous glomerulonephritis with moderate segmental sclerosis, as well as tubulointerstitial fibrosis with neutrophils, consistent with acute interstitial nephritis. Positive staining for PLA2R in the glomerular deposits suggested primary membranous nephropathy (MN). He was treated with prednisone first, and when the kidney biopsy was conclusive for membranous glomerulopathy, he was started on rituximab. On admission, he received hemodialysis intermittently, but this was stopped a month after discharge as his renal function normalized. Recently, there have been numerous cases reported with new onset of glomerular disease after receiving the COVID-19 vaccine. Further studies of vaccinated patients are needed to determine whether the severe acute respiratory syndrome coronavirus 2 virus vaccination is associated with a higher risk of MN and to identify potential predisposing factors and mechanisms of kidney injury in patients in whom it occurs.

Clinicopathological Characteristics and Outcomes of PLA2R-Associated Membranous Nephropathy in Seropositive Patients Without PLA2R Staining on Kidney Biopsy

Phospholipase A2 receptor (PLA2R)-associated membranous nephropathy (MN) with circulating serum autoantibodies to PLA2R (SAb+) but no deposits of PLA2R antigen in glomerular tissue by immunofluorescence (GAg-) has been reported. However, little is known about the clinicopathological characteristics or prognosis of this subtype of MN. Retrospective cohort study. 130 SAb+ patients in China with biopsy-proven MN who had follow-up data and received immunosuppressive therapy. The median follow-up was 16 (IQR, 9-25) months. PLA2R antigen detection by immunofluorescence staining of kidney biopsy specimens. Complete remission (CR) was defined as proteinuria levels<0.3 g/d and a >50% decreasecompared with a previously established baseline. Partial remission (PR) was defined as proteinuria levels<3.5 g/d and a >50% decrease compared with a previously established baseline. The kidney function outcome was defined as a >40% decrease in estimated glomerular filtration rate (eGFR) at the end of the study compared with baseline. Kaplan-Meier analysis of PR and CR comparing SAb+/GAg+ and SAb+/GAg- patients. Cox proportional hazards models to examine these associations were adjusted for confounders. Among 130 SAb+ patients with PLA2R-associated MN, 18 were GAg-. Compared with SAb+/GAg+ patients, those who were SAb+/GAg- presented with more severe kidney injury as evidenced by higher SAb titer, greater proteinuria, lower serum albumin concentrations, lower eGFR (all P< 0.05), and more severe disease with higher chronicity scores (P< 0.001) on kidney biopsies. SAb+/GAg- patients exhibited a significantly lower probability of PR (P< 0.001) and CR (P= 0.03) and were more likely to experience a >40% decrease in eGFR (P= 0.008) than patients who were SAb+/GAg+. After adjusting for clinical and pathologic variables available at the time of biopsy, compared with SAb+/GAg+ patients, SAb+/GAg- patients had a lower rate of experiencing remission (hazard ratio, 0.32 [95% CI, 0.15-0.68]; P= 0.003) and a higher rate of the >40% eGFR decrease outcome (hazard ratio, 7.66 [95% CI, 1.54-38.08]; P= 0.01). Retrospective study, small sample size, and lack of a uniform approach to treatment. Seropositive PLA2R-associated MN without PLA2R staining on kidney biopsy may represent a distinct clinical subtype with more severe disease and a worse prognosis. GAg- is independently associated with poor response to treatment and >40% eGFR decrease in seropositive PLA2R-associated MN.

The Prevalence of Mesangial Electron-Dense Deposits in PLA2R-Positive Membranous Nephropathy

Introduction: Membranous nephropathy (MN) is a common cause of nephrotic syndrome in adults and can be primary or secondary. The antigenic target of antibodies in 70% of primary cases is phospholipase A2 receptor (PLA2R). The presence or absence of mesangial electron-dense deposits has been used to distinguish between primary and secondary MN. Mesangial deposits suggest MN due to lupus, infection, or other causes, though they are reported to occur in approximately 10% of primary MN. Staining for PLA2R is now frequently used for confirming a diagnosis of primary MN. If mesangial deposits predict a secondary cause, they should be more frequent in PLA2R-negative biopsies. Methods: A review of institutional kidney biopsies between March 2017 and June 2020 identified all cases of MN. Cases with a diagnosis of lupus or near “full-house” staining by immunofluorescence microscopy (IF) were excluded. Light microscopy, IF, and electron microscopy (EM) were performed. PLA2R staining was performed by IF. EM for all cases was reviewed and electron-dense deposit location, distribution, and size were determined. Results: Ninety-three cases of MN were identified, of which 86 had both PLA2R staining and EM performed. Of these, 51 cases (59%) were positive for PLA2R and 35 (41%) were negative. Mesangial electron-dense deposits were present in 22 (25.6%) of the 86 cases, including 27.5% (14/51) of PLA2R-positive cases and 22.8% (8/35) of PLA2R-negative cases. No difference was seen in size or distribution of deposits, or other features considered suggestive of secondary MN. Conclusion: PLA2R-negative cases were not more likely to have mesangial deposits than PLA2R-positive cases. Mesangial deposits should not be used as an indicator of secondary MN.

Renal expression of PLA2R, THSD7A, and IgG4 in patients with membranous nephropathy and correlation with clinical findings.

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in nondiabetic adults. M-type phospholipase A2 receptor (PLA2R), thrombospondin type-1 domain-containing 7A (THSD7A) are known as target podocyte antigens in membranous nephropathy (MN). Antibodies against these podocyte antigens are used in the initiation of treatment and response monitoring. However, the relationship between renal podocyte antigens and treatment response is not clear yet. We evaluated the relationship between immunohistochemical PLA2R, THSD7A and IgG4 staining, clinical findings and treatment response in kidney biopsies. Fifty-eight patients with MN were included in this retrospective study. In the renal biopsy samples of the patients, PLA2R, THSD7A and IgG4 were stained immunohistochemically and evaluated by light microscopy. The clinical, laboratory and treatment results of the patients were obtained from the hospital records. The study included a total of 58 patients with MN and a mean follow-up period of 32.3±19.7months. In patients with primary MN; PLA2R, THSD7A and IgG4 were positive in 57.1% (n=28), 12.2% (n=6) and 69.4% (n=34), respectively. Only PLA2R staining was distinctly higher in patients with primary MN than secondary MN (P=.025). Dual positivity (PLA2R+THSD7A) was detected in five (10.2%) of patients with primary MN. We did not determine any relationship between the PLA2R, THSD7A and IgG4 staining patterns and treatment response of the patients. It was found no correlation between PLA2R, THSD7A and IgG4 staining in kidney tissue and treatment response. Interestingly, dual positivity (PLA2R+THSD7A) was detected only in primary MN.

Seropositive PLA2R-associated membranous nephropathy but biopsy-negative PLA2R staining.

Serum phospholipase A2 receptor (PLA2R) antibody (SAb) and glomerular deposits of PLA2R antigen (GAg) have been tested widely in idiopathic membranous nephropathy (MN). Recently, we noticed a special form of PLA2R-associated MN with positive circulating PLA2R antibody but negative PLA2R deposits in the glomeruli by immunofluorescence on frozen tissue (IF-F). The significance of this form of PLA2R-associated MN is yet to be elucidated. This study aimed to explore the clinicopathological features of these PLA2R-associated MN patients. This study enrolled 229 biopsy-proven PLA2R-associated MN patients with SAb+. SAb was measured by enzyme-linked immunosorbent assay, and GAg was detected by IF-F. These patients were divided into SAb+/GAg+ and SAb+/GAg- groups. Clinicopathological characteristics of SAb+/GAg+ and SAb+/GAg- PLA2R-associated MN patients were compared. PLA2R antigens of 19 SAb+/GAg- PLA2R-associated MN patients were verified by immunohistochemistry on paraffin tissue (IHC-P). Among 229 SAb+ PLA2R-associated MN patients, 210 (91.70%) were GAg+ and 19 (8.3%) were GAg-. These 19 SAb+/GAg- PLA2R-associated MN patients presented positive PLA2R deposits by IHC-P. Compared with SAb+/GAg+ PLA2R-associated MN patients, SAb+/GAg- PLA2R-associated MN patients had higher levels of serum PLA2R antibody (P = 0.004), increased proteinuria (P = 0.008), lower serum albumin (P = 0.019), more prominent chronic pathological lesions in terms of glomerulosclerosis score (P = 0.025), interstitial fibrosis score (P = 0.016), tubular atrophy score (P = 0.010) and total renal chronicity score (P = 0.010), and were more likely to be accompanied by focal segmental glomerulosclerosis (P = 0.014). Higher SAb level was associated with the total renal chronicity score (odds ratio per 100 RU/mL, 1.16; 95% confidence interval 1.01-1.33; P = 0.033). PLA2R-associated MN patients with seropositive PLA2R antibody but negative PLA2R deposits in the glomeruli by IF-F have higher levels of SAb and worse clinicopathological manifestations compared with their double-positive counterparts. IHC-P can be an alternative technique to reveal PLA2R glomerular deposits.

Membranous nephropathy in patients with HIV: a report of 11 cases

BackgroundMembranous nephropathy (MN) has been recognized to occur in patients with human immunodeficiency virus (HIV) infection since the beginning of the HIV epidemic. The prevalence of phospholipase A2 receptor (PLA2R)-associated MN in this group has not been well studied.MethodsWe conducted a retrospective review of electronic pathology databases at three institutions to identify patients with MN and known HIV at the time of renal biopsy. Patients with comorbidities and coinfections known to be independently associated with MN were excluded.ResultsWe identified 11 HIV-positive patients with biopsy-confirmed MN meeting inclusion and exclusion criteria. Patient ages ranged from 39 to 66 years old, and 10 of 11 patients (91%) were male. The majority of patients presented with nephrotic-range proteinuria, were on anti-retroviral therapy at the time of biopsy and had low or undetectable HIV viral loads. Biopsies from 5 of 10 (50%) patients demonstrated capillary wall staining for PLA2R. Measurement of serum anti-PLA2R antibodies was performed in three patients, one of whom had positive anti-PLA2R antibody titers. Follow-up data was available on 10 of 11 patients (median length of follow-up: 44 months; range: 4–145 months). All patients were maintained on anti-retroviral therapy (ARV) and 5 patients (52%) received concomitant immunosuppressive regimens. Three patients developed end-stage renal disease (ESRD) during the follow-up period.ConclusionsMN in the setting of HIV is often identified in the setting of an undetectable viral loads, and similar to other chronic viral infection-associated MNs, ~ 50% of cases demonstrate tissue reactivity with PLA2R antigen, which may be seen without corresponding anti-PLA2R serum antibodies.

Validation of phospholipase A2 receptor direct immunofluorescence staining in the diagnosis of primary membranous glomerulonephritis

Distinguishing between primary and secondary subtypes of membranous glomerulonephritis (MGN) is critical for its clinical management. We prospectively compared direct immunofluorescence (DIF) staining for phospholipase A2 receptor (PLA2R) on frozen renal biopsy with the presence of detectable serum PLA2R antibody assessed by enzyme linked immunosorbent assay (ELISA) in the diagnosis of primary MGN. Forty-six patients with biopsy-proven MGN were enrolled from April 2017 to June 2019 with 31/46 (67.4%) being primary and 15/46 (32.6%) being secondary as determined by comprehensive clinical assessment. This is currently deemed to be the gold standard for distinguishing primary from secondary MGN. Amongst the 31 primary MGN patients, 24/31 were positive on PLA2R DIF staining compared to 18/31 being positive on the PLA2R ELISA (p=0.03). Amongst the 15 secondary MGN patients, 1/15 was positive on PLA2R DIF compared to 0/15 on PLA2R ELISA (p=1.0). In conclusion, the presence of PLA2R staining on DIF demonstrated superior sensitivity and similar specificity compared to the detection of circulating PLA2R antibodies by ELISA in the diagnosis of primary MGN in a cohort of 46 patients with biopsy-proven MGN. We suggest that DIF should be considered as part of routine work-up in all newly diagnosed cases of MGN.

M-Type Phospholipase A2 Receptor Staining in Children with Idiopathic Membranous Nephropathy: PLA2R Staining in Children with IMN

Background: Membranous Nephropathy (MN) is a common cause of nephrotic syndrome in adults that can also occur in children, albeit less frequently. Recently, the M-type phospholipase A2 receptor (PLA2R) was identified as the target antigen in idiopathic membranous nephropathy (IMN), making it a useful marker for diagnosis. However, there are few studies describing the potential role of PLA2R in children with IMN. The aim of this study was to clarify the involvement of PLA2R in childhood IMN. Methods: We enrolled 11 patients diagnosed with IMN from January 1998 to March 2017. We performed PLA2R staining in paraffin-embedded renal biopsy sections. The clinical data were collected from the patients’ medical records. Results: The median age at biopsy was 6 years (range, 4 to 14 years). A single 6-year-old boy among all pediatric patients with IMN had granular PLA2R staining along his glomerular capillary loops and the prevalence of PLA2R-positivity was 9%. He also showed IgG4 co-dominant staining in terms of IgG subclass. There were no apparent differences in his clinical features such as clinical data at the time of renal biopsy, the time from the treatment initiation to remission, and relapse or renal dysfunction during the follow-up period. Conclusion: We suggest that PLA2R staining can be a diagnostic tool for patients with IMN of any age, though pediatric patients with IMN have lower prevalence of PLA2R-positive staining than adult patients.

SUN-030 PHOSPHOLIPASE A2 RECEPTOR AND THROMBOSPONDIN TYPE-1 DOMAIN-CONTAINING 7A IN MALIGNANCY MEMBRANOUS NEPHROPATHY

Phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A) have recently been identified as pathogenic antigens in patients with membranous nephropathy (MN). Notably, PLA2R is detected in a few patients with malignancy-associated MN. Furthermore, a high incidence of cancer is reported in patients with THSD7A-associated MN. It is thus necessary to clarify the usefulness of PLA2R and THSD7A in malignancy-associated MN. Serum anti-PLA2R antibodies and glomerular PLA2R expression were first screened in 36 patients with malignancy-associated MN by enzyme-linked immunosorbent assay (ELISA) and immunofluorescence, respectively, followed by examination of serum anti-THSD7A antibodies and glomerular THSD7A. THSD7A expression in cancer tissues was also assessed in 9 of the 36 patients. Among the 36 patients, 12 (33%) were positive for both glomerular PLA2R staining and serum anti-PLA2R antibodies, and 2 were positive for either glomerular PLA2R staining or serum anti-PLA2R antibodies. IgG4 was the dominant IgG subclass in PLA2R-related patients. One patient with positve glomerular PLA2R staining was also positive for THSD7A staining. Among the remaining 22 (61%) patients who were double negative for glomerular PLA2R staining and serum anti-PLA2R antibodies, 17 of 20 (85%) had IgG1 dominant deposits in glomeruli, and 2 (9%) were positive for glomerular THSD7A staining. Serum anti-THSD7A antibody was not detected in any of the 36 patients. Among the 9 patients with available cancer tissues, enhanced expression of THSD7A in the cancer tissues was observed for 5 (56%), and one also showed enhanced glomerular expression of THSD7A. Screening of glomerular PLA2R antigen and serum anti-PLA2R antibodies is necessary in patients with malignancy-associated MN, whereas the incidence of glomerular THSD7A antigen or circulating anti-THSD7A antibodies is uncommon.

Compared staining of the phospholipase A2 receptor in the glomeruli of Chinese adults and children with idiopathic membranous nephropathy

BackgroundThe identification of the M-type phospholipase A2 receptor (PLA2R) is a breakthrough recognized as a major target for adults with idiopathic membranous nephropathy (IMN). However, the role PLA2R played in pediatric patients with IMN, particularly in Chinese, has yet to be determined. MethodsThis retrospective study included 187 adult patients and 38 pediatric patients aged 17 years or younger with biopsy proved IMN. The pediatric cohort consisted of 27 children aged from 1 to 12 years and 11 children aged from 13 to 17. Glomerular expression of PLA2R was analyzed in stored, formalin-fixed, paraffin-embedded kidney biopsy sections. ResultsPLA2R staining in glomerular deposits was observed in 82.7% and 42.1% of adult and pediatric patients with IMN, respectively. The PLA2R-positive staining patients with IMN presented with more severe clinical features than PLA2R-negative staining patients in both adult and pediatric cohorts. When compared to the young children patients with IMN, the adolescents exhibited a higher positive rate of PLA2R staining (81.8% versus 25.9%), similar to the adult patients. ConclusionThe clinical features and prevalence of PLA2R positive staining in adolescent patients with IMN were similar to adult patients, suggesting that they probably have a close etiology and pathogenesis. However, most of the young children patients with IMN were PLA2R negative staining, suggesting a different underlying etiology.

Clinical and Histological Features of Phospholipase A2 Receptor-Associated and Thrombospondin Type-I Domain-containing 7A-Associated Idiopathic Membranous Nephropathy: A Single Center Retrospective Study from China

BackgroundM-type phospholipase A2 receptor (PLA2R) was identified as the major target antigen in idiopathic membranous nephropathy (IMN). Another target antigen, namely thrombospondin type-1 domain-containing 7A (THSD7A), was recently detected in approximately 10% of non-PLA2R-associated IMN. In this single center retrospective study, clinical and histological features of PLA2R-associated and THSD7A-associated IMN patients were evaluated.Material/MethodsA total of 192 IMN patients, who were receiving no glucocorticoids or immunosuppressant before renal biopsy, were enrolled in this study and followed for a median duration of 25.5 months. IMN with enhanced glomerular PLA2R and THSD7A staining by immunohistochemistry (IHC) were designated as PLA2R-associated IMN and THSD7A-associated IMN respectively. Serum anti-PLA2R and anti-THSD7A antibodies levels were assessed by enzyme linked immunosorbent assay and indirect immunofluorescence testing in PLA2R-associated and THSD7A-associated IMN.ResultsOf 192 IMN patients, 164 patients (85.4%) had PLA2R-associated IMN and 3 patients (1.6%) had THSD7A-associated IMN. Compared with non-PLA2R-associated IMN patients, the 24-hour urinary protein levels were significantly higher (P=0.008), whereas, the proteinuria remission rates were significantly lower (P=0.03) in PLA2R-associated IMN patients. No pathological differences were found between PLA2R-associated IMN and non-PLA2R-associated IMN. Among 3 THSD7A-associated IMN patients, 1 patient had elevated serum anti-THSD7A antibody levels, which was below detectable levels after achieving partial proteinuria remission with combined glucocorticoid and cyclosporine treatment.ConclusionsCompared with non-PLA2R-associated IMN patients in our cohort, PLA2R-associated IMN patients presented with more severe proteinuria and lower remission rates after treatment, with no distinct histological differences. Glomerular expression of PLA2R could be a useful marker to indicate the severity, treatment response, and prognosis of IMN.

Anti-neutrophil cytoplasmic antibody-associated glomerulonephritis with detection of myeloperoxidase and phospholipase A2 receptor in membranous nephropathy-lesions: report of two patients with microscopic polyangiitis

BackgroundPodocyte phospholipase A2 receptor (PLA2R) is a major target antigen in idiopathic adult membranous nephropathy (MN). Histological PLA2R staining in the renal tissue has proven to be useful for the detection of idiopathic MN. However, glomerular PLA2R deposits have also been recently observed in several patients with secondary MN, such as hepatitis B virus-associated, hepatitis C virus-associated, and neoplasm-associated MN. Certain inflammatory environments have been suggested to lead to abnormal expression of PLA2R epitopes, with the resulting production of PLA2R autoantibodies.Case presentationWe report two patients diagnosed with anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis with MN-lesions, in whom ANCA titers for myeloperoxidase (MPO) were persistently positive. The first patient was a 52-years-old man who presented with interstitial pneumonitis. Microscopic hematuria and proteinuria were found when the interstitial pneumonitis became more severe. Renal biopsy findings yielded a diagnosis of ANCA-associated glomerulonephritis (mixed class) with MN-lesions. The second patient was a 63-years-old woman who had been treated for relapsing polychondritis. Her renal tissue showed evidence of focal ANCA-associated glomerulonephritis with MN-lesions. Interestingly, both MPO and PLA2R were detected in the glomerular subepithelial deposits of both patients. Immunoglobulin G (IgG) 1 and IgG2 were positive in the glomeruli of patient 2, and all subclasses of IgGs were positive in patient 1.ConclusionThe present cases suggest that ANCA-associated glomerulonephritis could expose PLA2R, leading to the development of MN-lesions.

Validation of renal biopsy phospholipase A2 receptor staining on direct immunofluorescence in the diagnosis of primary membranous glomerulonephritis

Background: Membranous glomerulonephritis (MGN) is a major cause of non-diabetic nephrotic syndrome with approximately 75% of cases being primary and the rest secondary to aetiologies such as malignancy and autoimmune diseases. Enzyme linked immunosorbent assay (ELISA) for circulating M-type Phospholipase A2 Receptor (PLA2R) antibodies in serum is highly specific for identifying primary MGN but is limited in its sensitivity and turnaround time.

Correlation and discrepancy of phospholipase A2 receptor staining in membranous nephropathy in paraffin-embedded kidney biopsies.

Distinguishing primary from secondary forms of membranous nephropathy (MN) in paraffin-embedded kidney biopsies is challenging. Previous studies have measured the accuracy, sensitivity, and specificity of phospholipase A2 receptor (PLA2R) on MN. However, due to the absence of a gold standard method for diagnosis, further studies are necessary. Here, we measure the correlation and discrepancy of PLA2R on MN in paraffin-embedded kidney biopsies by correlating PLA2R findings with immunofluorescence (IF), light microscopy (LM), and electron microscopy (EM) results. A total of 116 kidney biopsies were investigated including 87 MN and 29 nonmembranous kidney diseases. PLA2R was examined by indirect IF assay. A total of 79 MN cases were subjected to PLA2R staining and histopathological analyses. The remaining eight cases were excluded due to the lack of the glomeruli in the sections. The correlation and discrepancy between PLA2R and IF findings were seen in 65.45% and 34.55%, respectively. PLA2R and EM findings showed a 65.52% correlation and 34.48% discrepancy. LM features and PLA2R findings showed a correlation of 58.44% and discrepancy of 41.56%. Overall correlation between histopathology and PLA2R was seen in 65.82% and 34.18% showed discordant cases. All 29 non-membranous MN cases were negative for PLA2R. Staining for PLA2R could be a useful adjunctive tool in the stratification of cases of MN. The findings of this study strongly recommend the use of PLA2R IF staining method as a routine test for all MN cases.