Clinicopathological characteristics of thrombospondin type 1 domain-containing 7A-associated membranous nephropathy

Prevalence and prognosis of malignancy in THSD7A-associated membranous nephropathy: a systematic literature review and clinical case study

BACKGROUND

This study aims to investigate the incidence and prognosis of malignancy in individuals with thrombospondin type-1 domain-containing 7A (THSD7A)-associated membranous nephropathy (MN).

METHODS

First, we performed a systematic literature review of prevalence of malignancy in THSD7A-associated MN. Then, we conducted a retrospective analysis of 454 patients diagnosed with MN through renal biopsy at our hospital between January 2016 and December 2020. We assessed the presence of serum anti-THSD7A antibodies and performed immunohistochemical staining of renal tissue for THSD7A. Subsequently, we followed patients with THSD7A-associated MN for a minimum of 3-5 years, collecting their clinical, pathological characteristics, and prognosis. Additionally, we conducted a literature review on patients with THSD7A-associated MN in conjunction with malignancy.

RESULTS

We identified a total of nine articles containing comprehensive data on THSD7A-associated MN and malignancy. Among 235 patients with THSD7A-positive MN, 36 individuals had concurrent malignancies, resulting in a malignancy prevalence of 13.3% (95% CI: 8.9-17.7%). In our center, we followed up with 15 patients diagnosed with THSD7A-associated MN and observed three cases of concomitant tumors: two cases of lung adenocarcinoma and one case of small cell lung cancer with multiple metastases. The prevalence of malignancy in our cohort was 20%. Notably, we detected positive THSD7A staining in both renal and lung cancer tissues in one patient with small cell lung cancer.

CONCLUSIONS

Patients with THSD7A-associated MN should undergo vigilant follow-up assessments, with a particular focus on actively seeking potential tumorigenic lesions to prevent misdiagnosis or oversight.

Specific antigens in malignancy-associated membranous nephropathy

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.

Clinicopathological and prognostic characteristics of idiopathic membranous nephropathy with dual antigen positivity

Background

Idiopathic membranous nephropathy (IMN) is the most common pathological type in adults with nephrotic syndrome. Many target antigens have been discovered. However, dual antigen-positive IMN patients are very rare, with only a few such cases being briefly described in various studies. There is no specific study on the clinicopathological and prognostic characteristics of dual antigen-positive IMN patients, and the disease characteristics of such patients remain unclear.

Methods

Immunohistochemical staining of PLA2R, THSD7A, and NELL-1 was conducted on kidney tissue samples obtained from patients diagnosed with IMN. Simultaneously, the presence of corresponding serum antibodies was determined. Patients exhibiting positivity for dual antigens were included in the study, identified either through tissue staining or serum antibody detection. We retrospectively collected their clinical, pathological, and follow-up data and measured their serum antibody levels at multiple time points. Additionally, the same type of dual antigen-positive IMN cases reported in the literature were reviewed to extract clinical, pathological, and prognostic information. We compared the data for all of the above dual antigen-positive and PLA2R single-positive IMN cases at our center.

Results

We identified 6 IMN patients with dual antigen positivity at our center, approximately 0.7% of whole MN series; the previous literature reports 43 IMN patients with dual antigen positivity, the proportion ranged from 0.2% to 2.8%. The IgG1 positivity rate in the renal tissue of the dual antigen-positive patients at our center was significantly lower than that of dual antigen-positive patients previously reported (16.7% vs. 100.0%, p=0.015), but there was no significant difference in clinical or prognostic aspects. Patients with dual antigen positivity reported at our center and in the literature were combined and compared with PLA2R single-positive IMN reported at our center. Compared with PLA2R single-positive IMN patients, dual antigen-positive IMN patients had a higher renal tissue IgG1 positivity rate (58.3% vs. 22.3%, p=0.016), and the time required to achieve remission was longer [13.5 (3.3,35.0) vs. 3.0 (1.0,8.0), p=0.052]. Overall, The changes in urine protein were consistent with the changes in serum PLA2R antibody levels in dual antigen-positive IMN patients.

Conclusions

For patients with primary membranous nephropathy who did not attain remission following prolonged treatment, multiple target antigen staining should still be actively performed, even with positivity for the PLA2R target antigen.

A Case of Spontaneous Remission of Membranous Nephropathy After the Removal of Nerve Epidermal Growth Factor-Like 1 Positive Sigmoid Colon Carcinoma

Recently, the association between membranous nephropathy (MN) and malignancy has been recognized in about 30% of epidermal growth factor-like 1 (NELL-1) positive cases. However, the mechanism of association with MN and malignancy remains under search. In this report, we present a unique case of MN with positive staining for both thrombospondin type-1 domain-containing 7A (THSD7A) and NELL-1. An 80-year-old Japanese woman with nephrotic syndrome (NS) was diagnosed as an immunoglobulin (Ig)G1 subclass predominant secondary MN with weakly positive for THSD7A staining. Then, advanced cancer in the sigmoid colon was found during screening tests for malignancy. After the removal of colon carcinoma, complete remission was achieved at 28 weeks follow-up after operation. Five years later, she remained in remission and passed without recurrence. Thereafter, we examined again newly reported NELL-1 in renal biopsy specimens and found very strong staining along the glomerular capillary walls. Moreover, in resected tumor tissues, NELL-1 was strongly positive at the basal side of adenocarcinoma cells, but THSD7A staining was negative. This case report provides clinical details and highlights the utility of autoantibodies, especially NELL-1, in the diagnosis and treatment of secondary MN with malignancy.

THSD7A as a Promising Biomarker for Membranous Nephrosis

Membranous nephropathy (MN) is an autoimmune disease of the kidney glomerulus and one of the leading causes of nephrotic syndrome. The disease exhibits heterogeneous outcomes with approximately 30% of cases progressing to end-stage renal disease. Traditionally, the standard approach of diagnosing MN involves performing a kidney biopsy. Nevertheless, kidney biopsy is an invasive procedure that poses risks for the patient including bleeding and pain, and bears greater costs for the health system. The clinical management of MN has steadily advanced owing to the identification of autoantibodies to the phospholipase A2 receptor (PLA2R) in 2009 and thrombospondin domain-containing 7A (THSD7A) in 2014 on the podocyte surface. At present, serum anti-PLA2R antibody detection and glomerular PLA2R antigen staining have been used for clinical diagnosis and prognosis, but the related detection of THSD7A has not been widely used in clinical practice. Here, we summarized the emerging knowledge regarding the roles THSD7A plays in MN and its clinical implications as diagnostic, prognostic, and therapeutic response as well as Methods for detecting serum THSD7A antibodies.

Histological transition from minimal change disease to THSD7A-associated membranous nephropathy in a patient receiving long-term steroid treatment: A case report

RATIONALE

A predominant Th2 immune response is suggested in the pathogenesis of both minimal change disease (MCD) and membranous nephropathy (MN); however, consecutive development of the 2 diseases in a patient is extremely rare.

PATIENT CONCERN

A Japanese man, who developed nephrotic syndrome in his 50s and was diagnosed with MCD by renal biopsy, experienced a relapse of proteinuria approximately 3 years later during long-term steroid treatment. Since the proteinuria was resistant to increase in steroid dosage, repeat renal biopsy was performed, which revealed a small amount of glomerular subepithelial immune deposits containing immunoglobulin (Ig)G (dominantly IgG4). Immunostaining for thrombospondin-type-1-domain-containing-7A (THSD7A) was positive on the glomerular capillary walls, whereas that for other causative antigens of MN, such as phospholipase A2 receptor or neural epidermal growth factor-like 1 protein, was negative. Detailed examination found no associated condition, including malignancies and allergic diseases.

DIAGNOSIS

The diagnosis of THSD7A-associated idiopathic MN was made.

INTERVENTIONS AND OUTCOMES

He received further increased dose of steroids. Thereafter he maintained clinical improvement because his urinary protein level was decreased.

LESSONS

The present case suggested that histological transition from MCD to MN is possible and repeat biopsy would be crucial for accurate diagnosis.

[Clinical significance of the determination of antibodies to thrombospondin type 1 containing domain 7A (THSD7A) in membranous nephropathy]

BACKGROUND

Membranous nephropathy (MN) is an immunocomplex glomerular disease, which is the most common cause of nephrotic syndrome in adults. Numerous studies have established that autoantibodies against the target podocyte autoantigens, including the thrombospondin type 1 domain containing 7A (THSD7A), play a leading role in the development of idiopathic MN.

AIM

To evaluate the prevalence of anti-THSD7A autoantibodies (anti-THSD7A AB) in a group of Russian patients with MN.

MATERIALS AND METHODS

Serum titers of anti-THSD7A AB were tested in 61 patients with biopsy-proven MN and 12 healthy controls.

RESULTS

The prevalence of anti-THSD7A AB was not differing significantly in patients with MN and in the control group (110.9 [71.63; 210.62] and 159.25 [125.64; 231.97] pg/ml, respectively; p=0.111). When comparing subgroups of anti-PLA2R-negative patients and patients who did not receive immunosuppressive therapy with the control group, there were also no statistically significant differences in the Anti-THSD7A AB levels (p>0.05). In the MN group, 1 (1.6%) patient was anti-THSD7A-positive: a 60-year-old man with anti-PLA2R-negative MN and the presence of hormonally inactive adenomas of both adrenal glands and colon polyps (villous adenoma with focal moderate dysplasia, tubulo-villous and tubular adenoma with focal moderate severe dysplasia).

CONCLUSION

THSD7-associated MN is a rare variant of MN and is usually detected in PLA2R-negative patients. Screening for malignancies in THSD7A-positive MN patients is proposed.

THSD7A Positivity Predicts Poor Survival and Is Linked to High FAK Expression and FGFR1-Wildtype in Female Patients with Squamous Cell Carcinoma of the Lung

Lung cancer is the leading cause of cancer-related deaths in the western world, with squamous cell carcinoma being one of the most common histological subtypes. Prognostic and predictive markers are still largely missing for squamous cell carcinoma of the lung (LSCC). Several studies indicate that THSD7A might at least play a role in the prognosis of different tumors. FAK seems to play an important role in lung cancer and is discussed as a potential therapeutic target. In addition, there is evidence that FAK-dependent signaling pathways might be affected by THSD7A. For that reason, we investigated the role of THSD7A as a potential tumor marker in LSCC and whether THSD7A expression has an impact on the expression level of FAK. A total of 101 LSCCs were analyzed by immunohistochemistry using tissue microarrays. THSD7A positivity was associated with poor overall survival in female patients and showed a relation to high FAK expression in this subgroup. To our knowledge, we are the first to report these correlations in lung cancer. The results might be proof of the assumed activation of FAK-dependent signaling pathways by THSD7A and that as a membrane-associated protein, THSD7A might serve as a putative therapeutic target in LSCC.

The Alternative Pathway Is Necessary and Sufficient for Complement Activation by Anti-THSD7A Autoantibodies, Which Are Predominantly IgG4 in Membranous Nephropathy

Membranous nephropathy (MN) is an immune kidney disease characterized by glomerular subepithelial immune complexes (ICs) containing antigen, IgG, and products of complement activation. Whereas proteinuria is caused by complement-mediated podocyte injury, the pathways of complement activation remain controversial due to the predominance of IgG4 in ICs, an IgG subclass considered unable to activate complement. THSD7A, a transmembrane protein expressed on podocytes, is the target autoantigen in ~3% of cases of primary MN. In this study, we analyzed sera from 16 patients with THSD7A-associated MN with regard to the anti-THSD7A IgG subclasses and their ability to fix complement in vitro. The serum concentration of anti-THSD7A IgG varied over two orders of magnitude (1.3-243 μg/mL). As a relative proportion of all IgG anti-THSD7A, IgG4 was by far the most abundant subclass (median 79%), followed by IgG1 (median 11%). IgG4 was the dominant subclass of anti-THSD7A antibodies in 14 sera, while IgG1 was dominant in one and co-dominant in another. One quarter of MN sera additionally contained low levels of anti-THSD7A IgA1. ICs formed by predominantly IgG4 anti-THSD7A autoantibodies with immobilized THSD7A were relatively weak activators of complement in vitro, compared to human IgG1 and IgG3 mAbs used as positive control. Complement deposition on THSD7A ICs was dose-dependent and occurred to a significant extent only at relatively high concentration of anti-THSD7A IgG. C3b fixation by THSD7A ICs was completely abolished in factor B-depleted sera, partially inhibited in C4-depleted sera, unchanged in C1q-depleted sera, and also occurred in Mg-EGTA buffer. These results imply that THSD7A ICs predominantly containing IgG4 activate complement at high IgG4 density, which strictly requires a functional alternative pathway, whereas the classical and lectin pathways are dispensable. These findings advance our understanding of how IgG4 antibodies activate complement.

Critical evaluation of cancer risks in glomerular disease

•

The increased cancer incidence in patients with glomerular disease can be secondary to an intrinsic immune dysfunction associated with the disease or/and extrinsic factors, especially immunosuppressants.

•

Paraneoplastic glomerulopathy is sometimes misdiagnosed as primary glomerulopathy.

•

The treatment for paraneoplastic glomerulopathy is different from primary glomerular disease.

•

In membranous nephropathy, serum circulating autoantibodies against PLA2R and THSD7A, immunohistochemical tissue markers for glomerular PLA2R, THSD7A and specific types of immunoglobulin G (IgG) may be used for identifying underlying malignancies.

•

A scheme of screening of cancers frequently reported in the setting of glomerular disease is important.

The increased cancer incidence in patients with glomerular disease can be secondary to an intrinsic immune dysfunction associated with the disease or/and extrinsic factors, especially immunosuppressants. The treatment for paraneoplastic glomerulopathy is different from primary glomerular disease. Immunosuppressive therapy often used for primary glomerulopathy may aggravate concomitant cancers in patients with paraneoplastic glomerulopathy. In membranous nephropathy (MN), measurement of serum circulating autoantibodies against podocyte transmembrane glycoprotein M-type phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain-containing 7A (THSD7A), immunohistochemical staining of kidney tissue for glomerular PLA2R, THSD7A, neural epidermal growth factor-like 1 protein (NELL-1) and specific types of immunoglobulin G (IgG) may be useful adjuncts when screening for underlying malignancies. This review addresses overall cancer risks in individuals with glomerular diseases and employment of biomarkers available for MN. We propose a scheme of screening of cancers frequently reported in the setting of glomerular disease.

The Role of Anti-PLA2R and Anti-THSD7A Antibodies in the Pathogenesis and Diagnostics of Primary Membranous Nephropathy: A Review of Current Knowledge for Clinical Practice

Primary membranous nephropathy (PMN) is considered a major cause of nephrotic syndrome. The discovery of circulating autoantibodies directed against glomerular podocytes helped to classify them as autoimmune diseases. Over the past years, there has been an increasing significance of anti-Phospholipase A2 Receptor (anti-PLA₂R), which has been detected in 70–80% of PMN cases, and relevance of anti-Thrombospondin type I domain-containing 7A (anti-THSD7A) even though they are present in 2–5% of patients. The results of clinical and experimental studies indicate that these antibodies are pathogenic. It radically changed the diagnostic and therapeutic approach. Measurement of antibody titers in the serum seems to be a valuable tool for identifying PMN and for the assessment of disease activity. By monitoring pathogenic antibodies levels rather than proteinuria or reduced glomerular filtration rate (GFR) as an indicator of glomerular disease, physicians would easier divide patients into those with active and inactive PMN disease and decide about their therapy. The aim of this review is to evaluate scientific evidence about the role of autoantibodies, namely anti-PLA₂R and anti-THSD7A, as PMN biomarkers. The present manuscript focuses on PMN pathogenesis and key data of diagnosis, monitoring of the disease, and treatment strategies that are currently being used in clinical practice.

Prevalence of neural epidermal growth factor-like 1- and exostosin 1/exostosin 2-associated membranous nephropathy: a single-center retrospective study in Japan

Membranous nephropathy (MN) is the leading cause of nephrotic syndrome in adults. We previously reported that the prevalence of phospholipase A2 receptor (PLA2R)- and thrombospondin type 1 domain containing 7A (THSD7A)-associated MN patients in Japan is 52.7% and 9.1%, respectively. In addition to PLA2R and THSD7A, we assessed the presence of newly discovered target antigens, neural epidermal growth factor-like 1 (NELL-1), semaphorin 3B (SEMA3B), and exostosin 1/exostosin 2 (Ext1/Ext2), in renal specimens from patients with primary and secondary MN by immunohistochemistry. We found enhanced glomerular staining of PLA2R, THSD7A, NELL-1, and Ext1/Ext2 in 53.6%, 8.7%, 1.5%, and 13.0% of the renal samples, respectively, in patients with primary MN. None of the patient specimens showed enhanced staining of SEMA3B. Enhanced glomerular staining of PLA2R, NELL-1, and Ext1/Ext2 was detected in 5.7%, 8.6%, and 22.9% of the patients with secondary MN, respectively. Based on our findings, we recommend the assessment of PLA2R, THSD7A and NELL-1 in addition to clinical information and IgG4 staining to differentiate between primary and secondary MN. This would aid in distinguishing secondary MN patients from primary MN patients who coincidentally have some secondary characteristics.

Spontaneous Remission of Thrombospondin Type-1 Domain-Containing-Associated Membranous Nephropathy

Membranous nephropathy often achieves spontaneous remission. However, there are scarce reports of spontaneous remission of thrombospondin type-1 domain-containing 7A (THSD7A)-associated membranous nephropathy. A 64-year-old female presented with nephrotic syndrome and edema of the lower extremities. We diagnosed membranous nephropathy by kidney biopsy and confirmed positive THSD7A on immunofluorescence using frozen sections; serum THSD7A antibodies were also detected. Thirty-four months after the initial diagnosis, she achieved a spontaneous complete remission without immunosuppressive therapy. With the complete remission, no serum THSD7A levels were detected. In this study, we describe serial examinations of kidney biopsies and serum THSD7A antibodies.

Advances in Understanding of Pathogenesis and Treatment of Immune-Mediated Kidney Disease: A Review

There continues to be rapid advancement in our understanding of the pathogenesis of immune-mediated kidney disease. This progress has culminated in the development of multiple therapeutic agents that have consistently improved renal and patient outcomes. The focus of this review is to discuss these recent advancements in immune-mediated kidney disease via the lens of direct and indirect immune-mediated mechanisms. In the direct immune-mediated disease, recently described antigens in anti-glomerular basement membrane (GBM) disease and membranous nephropathy are discussed, along with new therapeutic regimens in membranous nephropathy and focal segmental glomerulosclerosis. From an indirect immune-mediated disease standpoint, recent pivotal trials in antineutrophil cytoplasmic antibody vasculitis, lupus nephritis, and IgA nephropathy are examined from a real-world practice perspective. New molecular pathways in various disorders of alternate complement pathway are described, which in turn have led to development of various experimental therapies. In addition, pivotal and ongoing therapeutic trials in the aforementioned diseases are presented.

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

BACKGROUND

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.

METHODS

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.

RESULTS

The study included a total of 58 patients with MN and a mean follow-up period of 32.3 ± 19.7 months. 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.

CONCLUSION

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.

Pathophysiology, diagnosis, and treatment of membranous nephropathy

Nephrotic syndrome is in adult patients mainly due to membranous nephropathy (MN) characterized by thickening of the glomerular basement membrane (GBM) and immune complex formation between podocytes and the GBM. Autoantibodies directed against the M-type phospholipase A2 receptor (PLA2R) and thrombospondin 1 domain-containing 7 A (THSD7A) can be used as diagnostic biomarkers. THSD7A seems to be of direct pathogenic significance as is suggested by experimental models and plasmapheresis in humans. Recently, further antigens like NELL-1 (neural tissue encoding protein with EGF-like repeats-1), exostosin 1 and 2 have been discovered. Thus, MN should be classified into antibody positive and antibody negative MN. More specific immunosuppressive treatments directed against B-cells and antibody production like rituximab have been introduced in addition to already existing immunosuppressive protocols including steroids, chlorambucil, cyclophosphamide, and calcineurin inhibitors. Antibody removal using immunoadsorption or plasmapheresis leads to short-term reduction in proteinuria and might be indicated only in patients with very severe proteinuria and complications. Studies are needed to identify a more specific immunosuppression directed against the production and effects of autoantibodies in order to protect the kidneys from autoimmune mediated tissue damage and to identify patients who require an immunosuppressive treatment, as the remission rate is high in patients with MN.

A Target Antigen-Based Approach to the Classification of Membranous Nephropathy

OBJECTIVE

To describe the clinical and pathological phenotype of membranous nephropathy (MN) associated with M-type-phospholipase-A₂-receptor (PLA₂R), thrombospondin-type-1-domain-containing-7A (THSD7A), semaphorin 3B (SEMA3B), neural-epidermal-growth-factor-like-1-protein (NELL-1), protocadherin 7 (PCDH7), exostosin 1/exostosin 2 (EXT1/EXT2) and neural cell adhesion molecule 1 (NCAM-1) as target antigens.

METHODS

A retrospective cohort of 270 adult patients with biopsy-proven MN diagnosed between January 2015 and April 2020 was classified as PLA₂R-, THSD7A-, SEMA3B-, NELL-1-, PCDH7-, EXT1/EXT2-, NCAM-1-associated or septuple-negative MN using serologic tests, immunostaining, and/or mass spectrometry. Clinical, biochemical, pathologic, and follow-up data were systematically abstracted from the medical records, including disease activity of conditions traditionally associated with MN and occurring within 5 years of MN diagnosis.

RESULTS

Patients with PLA₂R-associated MN were predominantly middle-aged white men without associated disease. The presence of associated disease did not affect the clinical and pathologic characteristics of PLA₂R-associated MN, suggesting that they were coincidental rather than causally linked. THSD7A-, NELL-1-, PCDH7-, and NCAM-1-associated MN were rare and SEMA3B-associated MN was not discovered in our cohort. EXT1/EXT2-associated MN was primarily diagnosed in younger women with active systemic autoimmunity. A significant proportion of septuple-negative patients had associated malignancy or systemic autoimmunity.

CONCLUSION

The widely used distinction between primary and secondary MN has limitations. We propose a refined terminology that combines the target antigen and associated disease to better classify MN and guide clinical decision making.

Effects of phospholipase A2 receptor and thrombospondin type-1 domain-containing 7A expression in glomerular basement membranes on treatment response and renal outcome in membranous nephropathy

BACKGROUND

The aim of this study was to define the clinicopathologic features of phospholipase A₂ receptor (PLA₂R) and/or thrombospondin type-1 domain-containing 7A (THSD7A) associated membranous nephropathy(MN) focusing on their impact to disease relapse and response to treatment.

METHODS

A total of 201 patients were enrolled for baseline clinical and histopathological features and 102 patients with a clinical follow-up for more than 1 year were evaluated for outcomes. Immunohistochemical staining was performed with PLA₂R and THSD7A antibodies on kidney biopsies and glomerular staining was evaluated.

RESULTS

PLA₂R expression was observed in 75% of the patients' biopsies; however, THSD7A expression was present only in 7 patients' biopsies (3.5%). No significant difference was found between histopathological and clinical features of PLA₂R positive and negative patients, collectively. Glomerular PLA₂R expression was significantly associated with complete and complete/partial remission with first-line treatment; however, overall complete, and complete/partial remission rates did not differ from PLA₂R negative patients (p = 0.2 and p = 0.8). Male gender, the presence of IgG4 staining and a necessity of immunosuppressive treatment were significantly associated with glomerular PLA₂R expression. One patient, who developed end-stage renal disease, had glomerular expression for both PLA₂R and THSD7A. Three patients with THSD7A-positive MN achieved complete remission.

CONCLUSIONS

The probability of achieving complete remission is high in patients with PLA₂R-positive MN for whom the relapse rate was also higher. The overall renal outcome did not differ from PLA₂R negative cases. Low incidence of THSD7A-positive MN reduces the possibility of future randomized controlled trials.

Bevacizumab-associated glomerular microangiopathy that occurred after postoperative chemotherapy for ovarian cancer

Bevacizumab is a monoclonal antibody against vascular endothelial growth factor (VEGF) that is used to treat patients with various cancers. However, it is known to be associated with adverse events, such as hypertension and proteinuria. The histology of bevacizumab-induced nephropathy is known as thrombotic microangiopathy or minimal change nephrotic syndrome. Recently, however, the terms "bevacizumab-associated glomerular microangiopathy" and "anti-VEGF therapy-induced glomerular microangiopathy" have been proposed. We present a case of a 68-year-old woman who was administered postoperative chemotherapy (carboplatin, paclitaxel, and bevacizumab) for stage IV ovarian cancer. Proteinuria and hypertension appeared after three courses; however, six courses were completed. Then, gemcitabine and carboplatin were administered for recurrence of her cancer. She was diagnosed with nephrotic syndrome after eight courses. Renal biopsy showed accumulation of periodic acid-Schiff (PAS)-positive substances in the capillary walls and para-mesangial areas. Double contouring of basement membranes was also observed. Immunofluorescence microscopy revealed positive staining for IgG, IgA, IgM, C3, C4, and C1q. Immunosuppressive therapy was administered, but was ineffective. Further examination by electron microscopy and immunostaining led to a diagnosis of bevacizumab-associated glomerular microangiopathy.

Better remission rates in elderly Japanese patients with primary membranous nephropathy in nationwide real-world practice: The Japan Nephrotic Syndrome Cohort Study (JNSCS)

BACKGROUND

The aim of the present study was to clarify the prevalence of immunosuppressive drug use and outcomes in elderly and non-elderly patients with primary membranous nephropathy (MN) in nationwide real-world practice in Japan.

PATIENTS AND METHODS

Between 2009 and 2010, 374 patients with primary nephrotic syndrome were enrolled in the cohort study (The Japan Nephrotic Syndrome Cohort Study, JNSCS), including 126 adult patients with MN. Their clinical characteristics were compared with those of nephrotic patients with primary MN registered in a large nationwide registry (The Japan Renal Biopsy Registry, J-RBR). Outcomes and predictors in the elderly (≥ 65 years) and non-elderly groups were identified.

RESULTS

Similar clinical characteristics were observed in JNSCS patients and J-RBR patients (n = 1808). At the early stage of 1 month, 84.1% of patients were treated with immunosuppressive therapies. No significant differences were observed in therapies between age groups. However, elderly patients achieved complete remission (CR) more frequently than non-elderly patients, particularly those treated with therapies that included corticosteroids. No significant differences were noted in serum creatinine (sCr) elevations at 50 or 100%, end-stage kidney disease, or all-cause mortality between age groups. Corticosteroids were identified as an independent predictor of CR (HR 2.749, 95%CI 1.593-4.745, p = 0.000) in the multivariate Cox's model. sCr levels, hemoglobin levels, immunosuppressants, clinical remission, and relapse after CR were independent predictors of sCr × 1.5 or × 2.0.

CONCLUSION

Early immunosuppressive therapy including corticosteroids for primary MN showed better remission rates in elderly patients in a nationwide cohort study.

Advances in Pathogenesis of Idiopathic Membranous Nephropathy

Background

Membranous nephropathy (MN), a major cause of nephrotic syndrome, has attracted people's attention in recent years for its growing prevalence. It is the second or third leading cause of ESRD in patients with primary glomerulonephritis and is the leading glomerulopathy that recurs after kidney transplantation.

Summary

MN can be classified as idiopathic membranous nephropathy (IMN) and secondary MN. The discovery of the M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A) provides the new diagnostic methods and treatment strategies for IMN on the molecular level. The study on single nucleotide polymorphism of IMN genes, such as the single M-type phospholipase A2 receptor 1 (PLA2R1) gene and human leukocyte antigen (HLA) gene, explains the pathogenesis of the disease from the perspective of genetics and conforms to the trend of the era of precision medicine.

Key Messages

This review focuses on advances in the pathogenesis of IMN, including molecular and genetic pathogenesis, as well as discussing the diagnostic and treatment guiding value brought by these new discoveries.

Membranous nephropathy associated with thrombospondin type-1 domain-containing 7A (THSD7A) in an adult woman with eosinophilia

A 30-year-old woman on steroid therapy for eosinophilia presented with nephrotic syndrome during steroid tapering. She was diagnosed with membranous nephropathy (MN) stage II–III (positive for IgG1 and IgG4) by renal biopsy. There was no evidence of secondary MN. Her urinary protein level was controlled to 0.5 g/day or less, and her eosinophil count in white blood cell differential was stabilized at less than 10% without increasing the steroid dosage. The renal specimen did not show any enhanced granular expression of PLA2R along the glomerular basement membrane, and PLA2R was not detected in the patient’s serum. On retrospective analysis, enhanced granular staining for thrombospondin type-1 domain-containing 7A (THSD7A) in the glomeruli was detected in the biopsy, and anti-THSD7A IgG was detected in the serum using a commercial indirect immunofluorescence test (IFT). Based on these, the case was considered as THSD7A-associated MN with comorbid eosinophilia. The causal relationship between THSD7A-related MN and eosinophilia was unclear. However, a few cases of THSD7A-associated MN with eosinophilia have been reported, and further clarification on the relationship between THSD7A-related MN and eosinophilia is warranted.