Ocular manifestations of the genetic causes of focal and segmental glomerulosclerosis

Genetic forms of focal and segmental glomerulosclerosis (FSGS) often have extra-renal manifestations. This study examined FSGS-associated genes from the Genomics England Renal proteinuria panel for reported and likely ocular features. Thirty-two of the 55 genes (58%) were associated with ocular abnormalities in human disease, and a further 12 (22%) were expressed in the retina or had an eye phenotype in mouse models. The commonest genes affected in congenital nephrotic syndrome (NPHS1, NPHS2, WT1, LAMB2, PAX2 but not PLCE1) may have ocular manifestations . Many genes affected in childhood-adolescent onset FSGS (NPHS1, NPHS2, WT1, LAMB2, SMARCAL1, NUP107 but not TRPC6 or PLCE1) have ocular features. The commonest genes affected in adult-onset FSGS (COL4A3-COL4A5, GLA ) have ocular abnormalities but not the other frequently affected genes (ACTN4, CD2AP, INF2, TRPC6). Common ocular associations of genetic FSGS include cataract, myopia, strabismus, ptosis and retinal atrophy. Mitochondrial forms of FSGS (MELAS, MIDD, Kearn's Sayre disease) are associated with retinal atrophy and inherited retinal degeneration. Some genetic kidney diseases (CAKUT, ciliopathies, tubulopathies) that result in secondary forms of FSGS also have ocular features. Ocular manifestations suggest a genetic basis for FSGS, often help identify the affected gene, and prompt genetic testing. In general, ocular abnormalities require early evaluation by an ophthalmologist, and sometimes, monitoring or treatment to improve vision or prevent visual loss from complications. In addition, the patient should be examined for other syndromic features and first degree family members assessed.

Review of the Role of Rituximab in the Management of Adult Minimal Change Disease and Immune-Mediated Focal and Segmental Glomerulosclerosis

Background

Minimal change disease and primary FSGS are podocytopathies but are also immune-mediated diseases. Rituximab acts via multiple mechanisms by tilting the balance between autoreactive B and T cells in favor of regulatory B and T cells. The consequences are decreased production of cytokines, chemokines, and permeability factors by these cells. In the past decade, we have seen the discovery of autoantibodies mediating nephrotic syndrome (anti-annexin A2 antibody, anti-UCHL1 antibody, and anti-nephrin antibody), and rituximab decreases their production. Rituximab also binds to podocyte SMPDL3b and has direct podocyte actions.

Summary

Rituximab's role in managing these primary podocytopathies has been discussed in this brief review. Rituximab has been used extensively in children and adults with frequently relapsing and steroid-dependent nephrotic syndrome. However, rituximab is not very promising in adult steroid-resistant nephrotic syndrome. Although ofatumumab would cause prolonged B-cell depletion and is fully humanized, it is unclear if it is superior to rituximab in preventing relapse of nephrotic syndrome.

Key Messages

Rituximab therapy can induce prolonged remission in adults with frequently relapsing and steroid-dependent nephrotic syndrome. However, no good data exist on using rituximab in steroid-resistant nephrotic syndrome.

Treatment of post-transplant recurrent FSGS in children using plasmapheresis and augmentation of immunosuppression

Background

Up to 60% of pediatric renal transplant recipients with end-stage renal disease due to primary focal and segmental glomerulosclerosis (FSGS) may develop recurrent disease. Such recurrence is associated with poor prognosis if no remission is achieved. We report a single center experience with a protocol based on plasmapheresis and increased immunosuppression that resulted in a high long-lived remission rate.

Methods

This retrospective cohort study included consecutive pediatric renal transplant patients with recurrent FSGS treated with a standardized protocol using plasmapheresis and cyclophosphamide to supplement usual post-transplant immunosuppression with calcineurin inhibitors and steroids. Relapse was defined as urinary protein/creatinine ratio > 1.0 g/g and remission as < 0.5 g/g.

Results

Seventeen patients with FSGS recurrence post-transplant were treated. All had therapy resistant FSGS in native kidneys and had been on dialysis from 4 to 10 years. Of the 17, one died perioperatively from a pulmonary thromboembolism. Fifteen others achieved a complete remission within 3 months of treatment for FSGS recurrence. After a median follow-up period of 4 years, there were no recurrences of significant proteinuria. One patient achieved remission with rituximab.

Conclusion

The addition of plasmapheresis and cyclophosphamide to a calcineurin- and steroid-based immunosuppression regime was highly successful in inducing high remission rates with recurrent FSGS. Prospective trials are needed to evaluate further the efficacy of increased immunosuppression along with plasmapheresis in this setting.

Crystal-Induced Podocytopathy Producing Collapsing Focal Segmental Glomerulosclerosis in Monoclonal Gammopathy of Renal Significance: A Case Report

Monoclonal gammopathy–associated crystalline podocytopathy causing collapsing focal segmental glomerulosclerosis (FSGS) is very rare and has been associated with pamidronate therapy. We present the case of a 53-year-old man with vision loss secondary to corneal crystals deposition, nephrotic-range proteinuria, and reduced glomerular filtration rate without associated comorbid conditions. Two kidney biopsies were initially reported as primary FSGS but the patient did not respond to high-dose corticosteroid immunosuppression therapy. Repeat review of biopsies with additional electron microscopy analysis revealed crystalline inclusions in podocytes leading to collapsing FSGS. Subsequent workup revealed an immunoglobulin G κ serum monoclonal protein. Bone marrow biopsy revealed 5% κ-restricted plasma cells with cytoplasmic crystalline inclusions. To our knowledge, this is the first case of monoclonal gammopathy of clinical significance manifesting as crystalline podocytopathy leading to collapsing FSGS and keratopathy leading to vision loss. Crystalline podocytopathy should be considered in the differential diagnosis of collapsing glomerulopathy, and careful ultrastructural examination of the kidney biopsy specimen is crucial to establish this diagnosis.

RAGE and αVβ3-integrin are essential for suPAR signaling in podocytes

The soluble urokinase plasminogen activator receptor (suPAR) has been implicated in the pathogenesis of kidney diseases including primary and recurrent focal and segmental glomerulosclerosis (FSGS), diabetic nephropathy, and acute kidney injuries (AKI). Elevated serum suPAR concentration is a negative prognostic indicator in multiple critical clinical conditions. This study has examined the initial transduction steps used by suPAR in cultured mouse podocytes. We now report that the receptor for advanced glycation end-products (RAGE) co-immunoprecipitates with αV and β3 integrin subunits, which have been previously shown to initiate suPAR signal transduction at the podocyte cell surface. siRNA knock-down of RAGE attenuated Src phosphorylation evoked by either suPAR or by glycated albumin (AGE-BSA), a prototypical RAGE agonist. suPAR effects on Src phosphorylation were also blocked by the structurally dissimilar RAGE antagonists FPS-ZM1 and azeliragon, as well as by cilengitide, an inhibitor of outside-in signaling through αV-integrins. FPS-ZM1 also blocked Src phosphorylation evoked by AGE-BSA. FPS-ZM1 blocked increases in cell surface TRPC6 abundance, cytosolic reactive oxygen species (ROS) and activation of the small GTPase Rac1 evoked by either suPAR or AGE-BSA. In addition, FPS-ZM1 inhibited Src phosphorylation evoked by serum collected from a patient with recurrent FSGS during a relapse. The magnitude of this inhibition was indistinguishable from the effect produced by a neutralizing antibody against suPAR. These data suggest that orally bioavailable small molecule RAGE antagonists could represent a useful therapeutic strategy for a wide range of clinical conditions associated with elevated serum suPAR, including primary FSGS and AKI.

A case of dasatinib-induced focal segmental glomerulosclerosis in a patient with Philadelphia chromosome positive chronic myeloid leukemia

Focal segmental glomerulosclerosis is a common glomerular histological lesion, which is usually characterised by non-nephrotic range proteinuria or nephrotic syndrome. It may be idiopathic or occurs secondarily to drugs, diabetes, obesity or HIV nephropathy and other infections. Dasatinib, a tyrosine kinase inhibitor that has been used for the treatment of Philadelphia chromosome-positive chronic myeloid leukemia, has a few renal adverse effects. Exceptional cases with non-nephrotic range proteinuria have been reported in relation with dasatinib. In this case, we report a patient with symptoms of nephrotic syndrome and nephrotic range proteinuria, who was diagnosed as focal segmental glomerulosclerosis by kidney biopsy after treated with dasatinib.

Immunoadsorption for Recurrent Primary Focal Segmental Glomerulosclerosis on Kidney Allografts: A Single-Center Experience and Literature Review

INTRODUCTION

Primary focal and segmental glomerulosclerosis (FSGS) frequently reoccurs on kidney transplants and may lead to premature allograft loss. There are no guidelines for treating FSGS recurrence on allografts; treatment is based on apheresis (plasma exchange plasmapheresis [PP], semi-specific immunoadsorption [IA] with reusable columns) plus rituximab.

OBJECTIVE

We aimed to assess the efficacy of IA to treat recurrent FSGS.

METHODS

We report on 7 patients with recurrent FSGS on kidney allograft (proteinuria ≥3 g/g of urinary creatinine or ≥3 g/day); they all received IA. Our primary objective was to reduce proteinuria by >50%. Patients' mean age was 45 ± 10 years. Postoperative immunosuppression relied on steroids, mycophenolate mofetil, tacrolimus, with an induction therapy of basiliximab or antithymocyte globulins. Prophylaxis to prevent FSGS recurrence was either rituximab alone (n = 3), rituximab plus either PP or IA (n = 3), or no treatment (n = 1). Mean follow-up was 20 ± 13 months. There was a median of 72 (14-101) IA sessions per patient, that is, a mean of 14 ± 1 sessions per IA column.

RESULTS

At 12 months after starting IA, all patients had partial (n = 6) or complete (n = 1) remission, and allograft survival was 100%. The mean reduction in proteinuria within an IA session was 45 ± 15%. At last follow-up, 2 patients are in remission without IA, 3 patients are in partial remission that is IA dependent, and 2 patients lost their allograft due to FSGS recurrence. The most frequent adverse event was cytomegalovirus reactivation (n = 13), which subsided after valganciclovir therapy.

CONCLUSIONS

We show that recurrence of FSGS can be controlled long term with IA plus rituximab. However, some patients remained dependent on IA.

Emerging therapeutic strategies for minimal change disease and focal and segmental glomerulosclerosis

INTRODUCTION

Minimal change disease (MCD) and Focal and segmental glomerulosclerosis (FSGS) are two of the major causes of nephrotic syndrome (NS) in children and adults. According to KDIGO (Kidney Disease: Improving Global Outcomes) guidelines, the treatment of adult primary MCD and FSGS should be based on immunosuppressants and antiproteinuric drugs. Recently, Rituximab, a humanized monoclonal antibody (mAb) has emerged as a potential treatment for steroid or calcineurin inhibitor-dependent patients; it has however demonstrated lower efficacy in those with nephrotic syndrome that is resistant to the above indicated drugs.

AREAS COVERED

Analysis of ongoing and already completed clinical trials, retrieved from clinicaltrials.gov, clinicaltrialsregister.eu and PubMed involving new therapies for nephrotic syndrome secondary to MCD and FSGS.

EXPERT OPINION

The most promising drugs under investigation for MCD and FSGS are mAbs. We are hopeful that new therapeutic options to treat multi-drug resistant MCD and FSGS will emerge from currently ongoing studies. What appears certain is the difficulty in enrolling patients affected by orphan renal diseases and the selection of valid endpoints in clinical trials, such as kidney failure.

[Up to date of pathophysiology mechanism of idiopathic nephrotic syndromes: Minimal change disease and focal and segmental glomerulosclerosis]

Idiopathic nephrotic syndrome represents up to 30% of adult glomerulopathies. However, its prognosis according to remission, relapse and renal failure remains unchanged since the 80s and prediction remains difficult. Physiopathology of adult idiopathic nephrotic syndrome is complex and multifactorial, including immunologic and environmental factors and a putative permeability-circulating factor, still unknown. In this point of view, we propose to summarize actual knowledge about idiopathic minimal change disease and focal and segmental glomerulosclerosis physiopathology.

Regional variations in immunosuppressive therapy in patients with primary nephrotic syndrome: the Japan nephrotic syndrome cohort study

BACKGROUND

The lack of high-quality clinical evidences hindered broad consensus on optimal therapies for primary nephrotic syndromes. The aim of the present study was to compare prevalence of immunosuppressive drug use in patients with primary nephrotic syndrome across 6 regions in Japan.

METHODS

Between 2009 and 2010, 380 patients with primary nephrotic syndrome in 56 hospitals were enrolled in a prospective cohort study [Japan Nephrotic Syndrome Cohort Study (JNSCS)], including 141, 151, and 38 adult patients with minimal change disease (MCD), membranous nephropathy (MN), and focal segmental glomerulosclerosis (FSGS), respectively. Their clinical characteristics were compared with those of patients registered in a large nationwide registry of kidney biopsies [Japan Renal Biopsy Registry (J-RBR)]. The regional prevalence of use of each immunosuppressive drug was assessed among adult MCD, MN, and FSGS patients who underwent immunosuppressive therapy in the JNSCS (n = 139, 127, and 34, respectively). Predictors of its use were identified using multivariable-adjusted logistic regression models.

RESULTS

The clinical characteristics of JNSCS patients were comparable to those of J-RBR patients, suggesting that the JNSCS included the representatives in the J-RBR. The secondary major immunosuppressive drugs were intravenous methylprednisolone [n = 33 (24.6%), 24 (19.7%), and 9 (28.1%) in MCD, MN, and FSGS, respectively] and cyclosporine [n = 25 (18.7%), 62 (50.8%), and 16 (50.0%), respectively]. The region was identified as a significant predictor of use of intravenous methylprednisolone in MCD and MN patients.

CONCLUSION

Use of intravenous methylprednisolone for MCD and MN differed geographically in Japan. Its efficacy should be further evaluated in a well-designed trial.

Potential urine proteomics biomarkers for primary nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is a nonspecific kidney disorder, commonly caused by minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), and membranous nephropathy (MN). Here we analyzed urinary protein profiles, aiming to discover disease-specific biomarkers of these three common diseases in NS.

METHODS

Sixteen urine samples were collected from patients with biopsy-proven NS and healthy controls. After removal of high-abundance proteins, the urinary protein profile was analyzed by LC-MS/MS to generate a discovery set. For validation, ELISA was used to analyze the selected proteins in 61 urine samples.

RESULTS

The discovery set included 228 urine proteins, of which 22 proteins were differently expressed in MCD, MN, and FSGS. Among these, C9, CD14, and SERPINA1 were validated by ELISA. All three proteins were elevated in MCD, MN, and FSGS groups compared with in IgA nephropathy and healthy controls. When a regression model was applied, receiver operating characteristic analysis clearly discriminated MCD from the other causative diseases in NS.

CONCLUSIONS

We developed a disease-specific protein panel that discriminated between three main causes of NS. Through this pilot study, we suggest that urine proteomics could be a non-invasive and clinically available tool to discriminate MCD from MN and FSGS.

Parietal cells-new perspectives in glomerular disease

In normal glomeruli, parietal epithelial cells (PECs) line the inside of Bowman's capsule and form an inconspicuous sheet of flat epithelial cells in continuity with the proximal tubular epithelial cells (PTECs) at the urinary pole and with the podocytes at the vascular pole. PECs, PTECs and podocytes have a common mesenchymal origin and are the result of divergent differentiation during embryogenesis. Podocytes and PTECs are highly differentiated cells with well-established functions pertaining to the maintenance of the filtration barrier and transport, respectively. For PECs, no specific function other than a structural one has been known until recently. Possible important functions for PECs in the fate of the glomerulus in glomerular disease have now become apparent: (1) PECs may be involved in the replacement of lost podocytes; (2) PECs form the basis of extracapillary proliferative lesions and subsequent sclerosis in glomerular disease. In addition to the acknowledgement that PECs are crucial in glomerular disease, knowledge has been gained regarding the molecular processes driving the phenotypic changes and behavior of PECs. Understanding these molecular processes is important for the development of specific therapeutic approaches aimed at either stimulation of the regenerative function of PECs or inhibition of the pro-sclerotic action of PECs. In this review, we discuss recent advances pertaining to the role of PECs in glomerular regeneration and disease and address the major molecular processes involved.

The Fatty Kidney: Obesity and Renal Disease

Obesity-related glomerulopathy (ORG) is characterized by glomerulomegaly accompanied in many patients by lesions of focal and segmental glomerulosclerosis. Slowly increasing subnephrotic proteinuria is the commonest presentation of ORG. Occasionally, massive proteinuria (>5-10 g/day) is detected, but the typical findings of nephrotic syndrome are characteristically absent even in patients with massive proteinuria. Superimposed obesity can fuel the progression of other renal diseases, and a reduced number of functioning nephrons (of congenital or acquired causes) synergizes with obesity to induce end-stage renal disease. Weight loss, either induced by diet or bariatric surgery, and renin-angiotensin blockers are effective treatments to slow progression, but a significant proportion of cases will develop end-stage renal disease.

Balance between the two kinin receptors in the progression of experimental focal and segmental glomerulosclerosis in mice

Focal and segmental glomerulosclerosis (FSGS) is one of the most important renal diseases related to end-stage renal failure. Bradykinin has been implicated in the pathogenesis of renal inflammation, whereas the role of its receptor 2 (B2RBK; also known as BDKRB2) in FSGS has not been studied. FSGS was induced in wild-type and B2RBK-knockout mice by a single intravenous injection of Adriamycin (ADM). In order to further modulate the kinin receptors, the animals were also treated with the B2RBK antagonist HOE-140 and the B1RBK antagonist DALBK. Here, we show that the blockage of B2RBK with HOE-140 protects mice from the development of FSGS, including podocyte foot process effacement and the re-establishment of slit-diaphragm-related proteins. However, B2RBK-knockout mice were not protected from FSGS. These opposite results were due to B1RBK expression. B1RBK was upregulated after the injection of ADM and this upregulation was exacerbated in B2RBK-knockout animals. Furthermore, treatment with HOE-140 downregulated the B1RBK receptor. The blockage of B1RBK in B2RBK-knockout animals promoted FSGS regression, with a less-inflammatory phenotype. These results indicate a deleterious role of both kinin receptors in an FSGS model and suggest a possible cross-talk between them in the progression of disease.

Delayed development of pulmonary hemorrhage in a patient with positive circulating anti-neutrophil cytoplasmic antibody: a clinical dilemma

Detection of circulating anti-neutrophil cytoplasmic antibody (ANCA) provides a powerful clue in the diagnosis of vasculitis, but the clinical interpretation of the results is difficult in some cases. Here, we describe the case of a 65-year-old man who underwent hemodialysis due to focal segmental glomerulosclerosis and abruptly developed hemoptysis 14 years after a renal biopsy. At the time of the biopsy, computed tomography (CT) showed interstitial shadows in the lungs and pleural thickening, indicating pneumoconiosis that was accompanied by tuberculosis. Circulating myeloperoxidase-ANCA (10.5–32.5 U/ml) was subsequently noted, but the significance of this observation was unclear due to the preexisting disorders in the lungs and kidneys. Potent immunosuppressive therapies were avoided because of the pulmonary lesions and decreased renal function. There were few changes noted on follow-up CT, but infiltrative shadows emerged in the bilateral lungs, consistent with hemoptysis. The hemorrhagic shadows completely disappeared shortly after initiation of steroid therapy, with normalization of the serum ANCA level. Herein, we report this case, with an emphasis on the clinical dilemma faced in deciding the appropriate treatment. The findings in the case provide deep insights into clinical management of ANCA-positive patients.

Initially Nondiagnosed Fabry's Disease when Electron Microscopy Is Lacking: The Continuing Story of Focal and Segmental Glomerulosclerosis

Focal and segmental glomerulosclerosis is classified as either primary or secondary. We present a patient with a past history of biopsy-proven focal and segmental glomerulosclerosis. Despite initial response to dual blockade and steroids, proteinuria raised when steroids were decreased. After the patient was restarted on steroids, proteinuria did not improve. Another biopsy confirmed the previous diagnosis but suggested Fabry's disease, later confirmed by electron microscopy, α-galactosidase A serum and leukocyte deficiency as well as genetic studies. Proteinuria decreased when agalsidase β was prescribed in parallel with steroid tapering, increased with steroid discontinuation and improved with meprednisone administration. This report highlights the relevance of electron microscopy in kidney biopsy. In glomerulosclerosis, despite specific treatment, secondary hemodynamic and immunologic pathways may contribute to the development of proteinuria and accelerate the renal disease progression due to the primary disease. We discuss possible pathophysiologic pathways involved in proteinuria in Fabry's disease according to the biopsy and the therapeutic response.