Membranous nephropathy is a major etiology of nephrotic syndrome in adults and less frequently in children. Circulating antibodies to intrinsic podocyte antigens, such as M-type phospholipase A2 receptor, or to extrinsic proteins accumulate beneath the podocyte to cause damage via complement activation and/or other mechanisms. The availability of clinical testing for autoantibodies to M-type phospholipase A2 receptor has allowed noninvasive diagnosis of this form of membranous nephropathy and a means to monitor immunologic activity to guide immunosuppressive therapy. Treatment of membranous nephropathy includes optimal supportive care with renin-angiotensin-system blockers, lipid-lowering agents, diuretics, lifestyle changes, and additional immunosuppressive therapy in patients with an increased risk of progression to kidney failure. Rituximab has been recognized as a first-line immunosuppressive therapy for most membranous nephropathy patients with an increased risk of progressive disease, except those with life-threatening nephrotic syndrome or rapidly deteriorating kidney function from membranous nephropathy. This article discusses the major and minor antigens described in membranous nephropathy, the natural history of the disease, and guidelines for clinical management and immunosuppressive treatment.

UNASSIGNED: Serum-specific antibodies as a non-invasive means to effectively diagnose idiopathic membranous nephropathy and assess clinicopathology.
UNASSIGNED: Immunofluorescence of anti-PLA2R and THSD7A antibodies and kidney tissue PLA2R, THSD7A and IgG4 expression in IMN and non-IMN (2020-2021) was detected to assess the efficacy of diagnosing IMN. IMN patients were divided into two groups, anti-PLA2R antibody positive (161 cases) and negative (26 cases), and two groups, kidney tissue PLA2R (40 cases) and PLA2R+THSD7A (6 cases), to compare the clinical and pathological features, and to carry out a prognostic analysis of THSD7A-positive patients, with a focus on correlation with malignancy.
UNASSIGNED: The positive rate of anti-PLA2R antibodies was significantly higher in IMN (P<0.05); anti-PLA2R antibodies, kidney tissue PLA2R and IgG4 and THSD7A had some diagnostic value. Anti-PLA2R antibodies correlated with proteinuria levels in IMN patients, and their levels were negatively correlated with blood albumin (r=-0.146, P=0.042); correlated with pathological stage and C3 and IgG4 immunodeposition; there was no significant difference in clinical pathology between kidney tissue THSD7A+PLA2R positive compared to kidney tissue PLA2R positive patients, but the probability of achieving complete remission was low and time longer, and no malignancy events were detected during follow-up.
UNASSIGNED: Anti-PLA2R antibodies, kidney tissue PLA2R, THSD7A and IgG4 have high diagnostic efficacy for IMN; anti-PLA2R antibodies can be used as diagnostic markers to assist in the assessment of clinical and pathological features; co-expression of kidney tissue PLA2R and THSD7A is not significantly different from kidney tissue PLA2R in assessing the clinical features, pathological manifestations and prognosis, but requires long-term. However, long-term follow-up is needed to monitor the potential risk, and a larger multicentre study with long-term follow-up is expected to be conducted to comprehensively assess IMN characteristics.

Phospholipase A2 receptor (PLA2R)-associated membranous nephropathy is an important cause of nephrotic syndrome that can lead to a variety of systemic manifestations. Chylous ascites and bilateral renal vein thrombosis are rare manifestations in adult nephrotic syndrome, and there have been no reported cases demonstrating both chylous ascites and bilateral renal vein thrombosis in patients with PLA2R-associated membranous nephropathy. Here, we report the first case of PLA2R-associated membranous nephropathy complicated by renal vein thrombosis and chylous ascites successfully treated with anticoagulation and rituximab. A 65-year-old African American male presented with abdominal pain for four days, hematochezia for one day, and lower extremity edema for one year. Blood pressure was 158/73 mmHg and other vital signs were normal. Physical examination revealed abdominal distention, periumbilical tenderness, and bilateral lower extremity edema. Laboratory analysis showed high serum creatinine, hypoalbuminemia, hyperlipidemia, and proteinuria on 24-hour urine chemistry, all consistent with nephrotic syndrome. Abdominal computed tomography scan demonstrated nonocclusive bilateral renal vein thrombosis with ascites. Paracentesis revealed chylous ascites. Continuous heparin infusion was started for thrombosis. Esophagoduodenoscopy and colonoscopy did not reveal a source of bleeding. Serum anti-PLA2R was found positive, suggesting membranous nephropathy. Rituximab, along with warfarin switched from heparin, successfully controlled disease activity. Chylous ascites in nephrotic syndrome is thought to be associated with bowel edema. In our case, we hypothesize that renal vein thrombosis caused lymphatic fluid leakage by increasing lymphatic pressure. The case illustrates the importance of considering membranous nephropathy as a cause of chylous ascites and renal vein thrombosis. Development of lymphatic imaging techniques is warranted to clarify the pathophysiology.

Aim To study the clinical profile and course and to assess the outcome of patients with biopsy-proven primary membranous nephropathy (MN). Methods This study was carried out in a tertiary care hospital between December 2017 and December 2021 on four-year retrospective biopsy-proven patients with membranous nephropathy (MN). Urinary proteins, serum albumin, and serum creatinine were the baseline investigations that were performed. Special tests were done whenever necessary. Patients were treated with a modified Ponticelli (MP) regimen whenever needed. Patients were followed up after treatment administration for a minimum of a year. Results The study was done in 48 biopsy-proven MN patients. Thirty-six patients had primary MN with a mean age of 47+/-11.7 years. The male-female ratio was 2.6:1. Hypertension was present in 39% (14 patients), microscopic hematuria in 28% (10 patients), and acute kidney injury in 22% (8 patients). The mean 24-hour urinary protein was 11.2+/-2.9 g/day. PLA2R was positive in 78% (28 patients) of primary MN patients. Spontaneous remission was noted in 13.8% (5 patients) who were treated conservatively. Spontaneous remission was associated with lower baseline proteinuria (p<0.001), higher baseline serum albumin (p<0.001), and PLA2R negativity (p=0.04). Complete or partial treatment response was noted in 74.2% (23 patients). Treatment remission was associated with lower baseline proteinuria (p=0.018). Secondary membranous nephropathy (secondary MN) was diagnosed in 12 patients. Eleven were class V lupus nephritis, all women, and one male person living with HIV/AIDS (PLHA). Conclusions The majority of our primary MN patients were PLA2R positive on renal biopsy. Statistically significant factors associated with spontaneous remission were lower proteinuria, higher serum albumin at baseline, and PLA2R negativity. Treatment response was associated with lower proteinuria at presentation. The most common cause of secondary MN was lupus nephritis.

Membranous nephropathy (MN), an autoimmune disease, can manifest at any age and is among the most common causes of nephrotic syndrome in adults. In 80% of cases, the specific etiology of MN remains unknown, while the remaining cases are linked to drug use or underlying conditions like systemic lupus erythematosus, hepatitis B virus, or malignancy. Although about one-third of patients may achieve spontaneous complete or partial remission with conservative management, another third face an elevated risk of disease progression, potentially leading to end-stage renal disease within 10 years. The identification of phospholipase A2 receptor as the primary target antigen in MN has brought about a significant shift in disease management and monitoring. This review explores recent advancements in the pathophysiology of MN, encompassing pathogenesis, clinical presentations, diagnostic criteria, treatment options, and prognosis, with a focus on emerging developments in pathogenesis and therapeutic strategies aimed at halting disease progression. By synthesizing the latest research findings and clinical insights, this review seeks to contribute to the ongoing efforts to enhance our understanding and management of this challenging autoimmune disorder.

BACKGROUND: Sarcoidosis is a multisystemic inflammatory disease, characterized by the presence of non-caseating, epithelioid granulomas. Glomerular disease in patients with sarcoidosis is rare and membranous nephropathy (MN) is cited as the most common. The association between the two diseases remained unclear. This article reported a case of co-occurrence of sarcoidosis and anti-PLA2R-associated MN, to provide a possible relationship between these two entities.
METHODS: A 61-year-old Chinese Han woman with a history of sarcoidosis was admitted to our hospital for nephrotic syndrome. Her sarcoidosis was diagnosed according to the adenopathy observed on the computed tomography scan and the biopsy of lymph nodes. The MN presented with nephrotic syndrome with a PLA2R antibody titer of 357RU/ml, and the final diagnosis was based on a renal biopsy. The patient\'s sarcoidosis was remitted after treatment with prednisone. One year later MN was diagnosed, and she was treated with prednisone combined with calcineurin inhibitors, based on a full dose of renin-angiotensin system (RAS) inhibitor. The patient\'s sarcoidosis had been in remission while the MN was recurrent, and her renal function deteriorated to end-stage renal disease 6 years later due to discontinuation of immunosuppression. A genetic test led to the identification of the HLA-DRB1*0301 and HLA-DRB1*150 genes associated with both sarcoidosis and MN, which provides a new possible explanation of the co-occurrence of these two diseases.
CONCLUSIONS: This case suggested for the first time a potential genetic connection between idiopathic MN and sarcoidosis which needs further studies in the future.

UNASSIGNED: In recent years, the incidence of malignancy patients with membranous nephropathy (MN) has gradually increased, but the clinical and pathological characteristics of these patients are still unclear. Our study aims at elucidating the clinical and pathological characteristics of malignancy patients with MN, especially the expression patterns of MN-specific antigens in both kidney and tumor tissue.
UNASSIGNED: A retrospective analysis was performed to summarize the clinical and pathological data of MN patients with malignancy at Beijing Anzhen Hospital from January 1, 2012, to December 31, 2022, followed by a thorough review of relevant literature published between May 1, 2000 to May 1, 2023 and case aggregation.
UNASSIGNED: 19 patients in our center\'s MN cohort and 21 patients from literature review were diagnosed with malignancy either before or after being diagnosed with MN. Among them, 16 (40.0%) and 17 (42.5%) patients tested PLA2R-only and THSD7A-only positive in renal tissue, respectively. And 16 of 26 patients showed similar staining in tumor and kidney tissues. Compared to the idiopathic membranous nephropathy (IMN) patients at our center, patients with malignancy were older, had a lower estimated glomerular filtration rate, and had a lower rate of partial or complete response to treatment. Renal tissue from MN patients with concomitant malignancy was less frequently PLA2R-positive, more frequently THSD7A-positive, and more often glomerular IgG subclass IgG2 (P = 0.033) but less frequently IgG4 (P < 0.001).
UNASSIGNED: The clinical and pathological characteristics of MN patients with concomitant malignancy are different from those of IMN patients. Active screening for malignancy should be performed in non-PLA2R-positive elderly MN patients with a poor therapeutic response. Staining for MN target antigens in kidney and tumor tissues may be inconsistent, and the role of MN target antigens needs to be further explored.

The pathogenic role of anti-phospholipase A2 receptor (PLA2R) antibodies in primary membranous nephropathy (MN) has been well-established. This study aimed to identify potential small-molecule inhibitors against the PLA2R-antibody interaction, offering potential therapeutic benefits. A comprehensive screening of over 4000 small-molecule compounds was conducted by ELISA to assess their inhibitory effects on the binding between the immobilized full-length extracellular PLA2R and its antibodies. The affinity of anti-PLA2R IgG from MN patients and the inhibitory efficacy of each compound were evaluated via surface plasmon resonance (SPR). Human podocyte injuries were analyzed using CCK-8 assay, wound healing assay, western blot analysis, and immunofluorescence, after exposure to MN plasma +/- blocking compound. Fifteen compounds were identified as potential inhibitors, demonstrating inhibition rates >20 % for the PLA2R-antibody interaction. Anti-PLA2R IgG exhibited a consistent affinity among patients (KD = 10-8 M). Macrocarpal B emerged as the most potent inhibitor, reducing the antigen-antibody interaction by nearly 30 % in a dose-dependent manner, comparable to the performance of the 31-mer peptide from the CysR domain. Macrocarpal B bound to the immobilized PLA2R with an affinity of 1.47 × 10-6 M, while showing no binding to anti-PLA2R IgG. Human podocytes exposed to MN plasma showed decreased podocin expression, impaired migration function, and reduced cell viability. Macrocarpal B inhibited the binding of anti-PLA2R IgG to podocytes and reduced the cellular injuries.

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Membranous nephropathy (MN) is a glomerular disease mediated by autoimmune complex deposition, with approximately 30% of cases attributed to secondary causes. Among them, malignant tumors are a significant cause of secondary MN. Recent advancements in the identification of MN-specific antigens, such as THSD7A and NELL-1, suggest a potential association with malignant tumors, yet definitive proof of this relationship remains elusive. Therefore, this article aims to review the distribution of MN-specific antigens in patients with MN caused by malignant tumors and the possible role of these antigens in the pathogenesis of the disease.