Congenital nephrotic syndrome and recurrence of proteinuria after renal transplantation

Nephrotic Syndrome Throughout Childhood: Diagnosing Podocytopathies From the Womb to the Dorm

The etiologies of podocyte dysfunction that lead to pediatric nephrotic syndrome (NS) are vast and vary with age at presentation. The discovery of numerous novel genetic podocytopathies and the evolution of diagnostic technologies has transformed the investigation of steroid-resistant NS while simultaneously promoting the replacement of traditional morphology-based disease classifications with a mechanistic approach. Podocytopathies associated with primary and secondary steroid-resistant NS manifest as diffuse mesangial sclerosis, minimal change disease, focal segmental glomerulosclerosis, and collapsing glomerulopathy. Molecular testing, once an ancillary option, has become a vital component of the clinical investigation and when paired with kidney biopsy findings, provides data that can optimize treatment and prognosis. This review focuses on the causes including selected monogenic defects, clinical phenotypes, histopathologic findings, and age-appropriate differential diagnoses of nephrotic syndrome in the pediatric population with an emphasis on podocytopathies.

Long-term mortality in pediatric solid organ recipients-A nationwide study

BACKGROUND

The present study aimed at investigating long-term mortality of patients who underwent solid organ transplantation during childhood and at identifying their causes of death.

METHODS

A cohort of 233 pediatric solid organ transplant recipients who had a kidney, liver, or heart transplantation between 1982 and 2015 in Finland were studied. Year of birth-, sex-, and hometown-matched controls (n = 1157) were identified using the Population Register Center registry. The Causes of Death Registry was utilized to identify the causes of death.

RESULTS

Among the transplant recipients, there were 60 (25.8%) deaths (median follow-up 18.0 years, interquartile range of 11.0-23.0 years). Transplant recipients' risk of death was nearly 130-fold higher than that of the controls (95% CI 51.9-1784.6). The 20-year survival rates for kidney, liver, and heart recipients were 86.1% (95% CI 79.9%-92.3%), 58.5% (95% CI 46.2%-74.1%), and 61.4% (95% CI 48.1%-78.4%), respectively. The most common causes of death were cardiovascular diseases (23%), infections (22%), and malignancies (17%). There were no significant differences in survival based on sex or transplantation era.

CONCLUSION

The late mortality is still significantly higher among pediatric solid organ recipients in comparison with controls. Cardiovascular complications, infections, and cancers are the main causes of late mortality for all studied transplant groups. These findings emphasize the cruciality of careful monitoring of pediatric transplant recipients in order to reduce long-term mortality.

Steroid-Resistant Nephrotic Syndrome-Associated MYO1E Mutations Have Differential Effects on Myosin 1e Localization, Dynamics, and Activity

BACKGROUND

Myo1e is a nonmuscle motor protein enriched in podocytes. Mutations in MYO1E are associated with steroid-resistant nephrotic syndrome (SRNS). Most of the MYO1E variants identified by genomic sequencing have not been functionally characterized. Here, we set out to analyze two mutations in the Myo1e motor domain, T119I and D388H, which were selected on the basis of protein sequence conservation.

METHODS

EGFP-tagged human Myo1e constructs were delivered into the Myo1e-KO mouse podocyte-derived cells via adenoviral infection to analyze Myo1e protein stability, Myo1e localization, and clathrin-dependent endocytosis, which is known to involve Myo1e activity. Furthermore, truncated Myo1e constructs were expressed using the baculovirus expression system and used to measure Myo1e ATPase and motor activity in vitro.

RESULTS

Both mutants were expressed as full-length proteins in the Myo1e-KO cells. However, unlike wild-type (WT) Myo1e, the T119I variant was not enriched at the cell junctions or clathrin-coated vesicles (CCVs). In contrast, D388H variant localization was similar to that of WT. The rate of dissociation of the D388H variant from cell-cell junctions and CCVs was decreased, suggesting this mutation affects Myo1e interactions with binding partners. ATPase activity and ability to translocate actin filaments were drastically reduced for the D388H mutant, supporting findings from cell-based experiments.

CONCLUSIONS

T119I and D388H mutations are deleterious to Myo1e functions. The experimental approaches used in this study can be applied to future characterization of novel MYO1E variants associated with SRNS.

Monogenic focal segmental glomerulosclerosis: A conceptual framework for identification and management of a heterogeneous disease

Focal segmental glomerulosclerosis (FSGS) is not a disease, rather a pattern of histological injury occurring from a variety of causes. The exact pathogenesis has yet to be fully elucidated but is likely varied based on the type of injury and the primary target of that injury. However, the approach to treatment is often based on the degree of podocyte foot process effacement and clinical presentation without sufficient attention paid to etiology. In this regard, there are many monogenic causes of FSGS with variable presentation from nephrotic syndrome with histological features of primary podocytopathy to more modest degrees of proteinuria with limited evidence of podocyte foot process injury. It is likely that genetic causes are largely underdiagnosed, as the role and the timing of genetic testing in FSGS is not established and genetic counseling, testing options, and interpretation of genotype in the context of phenotype may be outside the scope of practice for both nephrologists and geneticists. Yet most clinicians believe that a genetic diagnosis can lead to targeted therapy, limit the use of high-dose corticosteroids as a therapeutic trial, and allow the prediction of the natural history and risk for recurrence in the transplanted kidney. In this manuscript, we emphasize that genetic FSGS is not monolithic in its presentation, opine on the importance of genetic testing and provide an algorithmic approach to deployment of genetic testing in a timely fashion when faced with a patient with FSGS.

A multidisciplinary nephrogenetic referral clinic for children and adults-diagnostic achievements and insights

BACKGROUND

Genetic kidney diseases contribute a significant portion of kidney diseases in children and young adults. Nephrogenetics is a rapidly evolving subspecialty; however, in the clinical setting, increased use of genetic testing poses implementation challenges. Consequently, we established a national nephrogenetics clinic to apply a multidisciplinary model.

METHODS

Patients were referred from different pediatric or adult nephrology units across the country if their primary nephrologist suspected an undiagnosed genetic kidney disease. We determined the diagnostic rate and observed the effect of diagnosis on medical care. We also discuss the requirements of a nephrogenetics clinic in terms of logistics, recommended indications for referral, and building a multidisciplinary team.

RESULTS

Over 24 months, genetic evaluation was completed for a total of 74 unrelated probands, with an age range of 10 days to 72 years. The most common phenotypes included congenital anomalies of the kidneys and urinary tract, nephrotic syndrome or unexplained proteinuria, nephrocalcinosis/nephrolithiasis, tubulopathies, and unexplained kidney failure. Over 80% of patients were referred due to clinical suspicion of an undetermined underlying genetic diagnosis. A molecular diagnosis was reached in 42/74 probands, yielding a diagnostic rate of 57%. Of these, over 71% of diagnoses were made via next generation sequencing (gene panel or exome sequencing).

CONCLUSIONS

We identified a substantial fraction of genetic kidney etiologies among previously undiagnosed individuals which influenced subsequent clinical management. Our results support that nephrogenetics, a rapidly evolving field, may benefit from well-defined multidisciplinary co-management administered by a designated team of nephrologist, geneticist, and bioinformatician. A higher resolution version of the Graphical abstract is available as Supplementary information.

Emerging Role of Clinical Genetics in CKD

Chronic kidney disease (CKD) afflicts 15% of adults in the United States, of whom 25% have a family history. Genetic testing is supportive in identifying and possibly confirming diagnoses of CKD, thereby guiding care. Advances in the clinical genetic evaluation include next-generation sequencing with targeted gene panels, whole exome sequencing, and whole genome sequencing. These platforms provide DNA sequence reads with excellent coverage throughout the genome and have identified novel genetic causes of CKD. New pathologic genetic variants identified in previously unrecognized biological pathways have elucidated disease mechanisms underlying CKD etiologies, potentially establishing prognosis and guiding treatment selection. Molecular diagnoses using genetic sequencing can detect rare, potentially treatable mutations, avoid misdiagnoses, guide selection of optimal therapy, and decrease the risk of unnecessary and potentially harmful interventions. Genetic testing has been widely adopted in pediatric nephrology; however, it is less frequently used to date in adult nephrology. Extension of clinical genetic approaches to adult patients may achieve similar benefits in diagnostic refinement and treatment selection. This review aimed to identify clinical CKD phenotypes that may benefit the most from genetic testing, outline the commonly available platforms, and provide examples of successful deployment of these approaches in CKD.

Evaluation of Genetic Kidney Diseases in Living Donor Kidney Transplantation: Towards Precision Genomic Medicine in Donor Risk Assessment

Purpose of Review

To provide a comprehensive update on the role of genetic testing for the evaluation of kidney transplant recipient and living donor candidates.

Recent Findings

The evaluation of candidates for living donor transplantation and their potential donors occurs within an ever-changing landscape impacted by new evidence and risk assessment techniques. Criteria that were once considered contraindications to living kidney donation are now viewed as standard of care, while new tools identify novel risk markers that were unrecognized in past decades. Recent work suggests that nearly 10% of a cohort of patients with chronic/end-stage kidney disease had an identifiable genetic etiology, many whose original cause of renal disease was either unknown or misdiagnosed. Some also had an incidentally found genetic variant, unrelated to their nephropathy, but medically actionable. These patterns illustrate the substantial potential for genetic testing to better guide the selection of living donors and recipients, but guidance on the proper application and interpretation of novel technologies is in its infancy. In this review, we examine the utility of genetic testing in various kidney conditions, and discuss risks and unresolved challenges. Suggested algorithms in the context of related and unrelated donation are offered.

Summary

Genetic testing is a rapidly evolving strategy for the evaluation of candidates for living donor transplantation and their potential donors that has potential to improve risk assessment and optimize the safety of donation.

Congenital Nephrotic Syndrome of the Finnish Type in a Dominican Newborn: An Overview and Case Report

Congenital nephrotic syndrome of the Finnish type (CNS-FT) is a rare genetic condition that causes massive proteinuria, hypoproteinemia, hypercholesterolemia, and edema that progresses to end-stage renal disease. Symptoms may manifest in utero as fetal hydrops or during the first few days to months of life. This article shares the case of a Dominican infant who presented with CNS-FT. It provides a comprehensive overview of CNS-FT including the underlying genetic cause, prenatal and postnatal diagnostic testing options, and treatment recommendations. It walks the reader through the diagnostic and initial and longer-term management of this infant and provides patient outcome at 10 months of age.

COQ8B glomerular nephropathy: Outcomes after kidney transplantation and analysis of characteristics in Chinese population

BACKGROUND

Mutation in the COQ8B gene can cause COQ8B glomerular nephropathy (COQ8B-GN), which is rare and associated with steroid-resistant nephrotic syndrome (SRNS) as well as rapid progression to end-stage renal disease (ESRD). The aim of this study was to analyze the prognosis and recurrence risk of COQ8B-GN in patients after kidney transplantation (KTx) and summarize the characteristics of the Chinese population.

METHODS

A retrospective study included four cases treated in our hospital with a diagnosis of COQ8B-GN. Chinese and foreign studies were searched from database inception to February 2022.

RESULTS

A total of four cases were included, with the age of onset ranging from 4 to 9 years. The initial presentations were SRNS and asymptomatic proteinuria. Only one had an extrarenal manifestation (thyroid cyst). All patients progressed to ESRD at a mean time of 42 months after onset. With a total follow-up time ranging from 12 to 87 months, three of them had received transplantation. While one case needed a second KTx due to graft failure caused by chronic rejection, two recipients had excellent graft function. No recurrence in allograft was observed. There have been 18 cases of KTx recipients reported globally with follow-up information. Except for two cases of graft failure caused by hyperacute rejection and chronic rejection, respectively, the rest all had good graft function without recurrence. In addition, 44 cases of COQ8B-GN in the Chinese population were identified. At the onset, 75% of the patients were aged ≤10 years with initial symptoms of asymptomatic proteinuria, nephrotic syndrome (NS), or SRNS. By the time of literature publication, 59% of patients had progressed to ESRD (mean age of 10.3 ± 3.6 years). The median time from onset to ESRD was 21 months. Renal pathology mainly showed focal segmental glomerulosclerosis (FSGS), accounting for 61.8% of all biopsies, followed by mesangial proliferative glomerulonephritis (20.6%). The first three prevalent mutations in the COQ8B gene among the Chinese population were c. 748G>C, c. 737G>A, and c. 532C>T.

CONCLUSION

COQ8B-GN in the Chinese population may present with asymptomatic proteinuria, NS, or SRNS initially, with most onsets before the age of 10 years. A lot of patients progress to ESRD in early adolescence. FSGS on biopsy and c. 748G>C in the genetic test are the most frequently seen in Chinese COQ8B-GN patients. KTx is feasible for patients with ESRD due to the low risk of recurrence, but we should pay attention to graft rejection.

Discovery of Autoantibodies Targeting Nephrin in Minimal Change Disease Supports a Novel Autoimmune Etiology

BACKGROUND

Failure of the glomerular filtration barrier, primarily by loss of slit diaphragm architecture, underlies nephrotic syndrome in minimal change disease. The etiology remains unknown. The efficacy of B cell-targeted therapies in some patients, together with the known proteinuric effect of anti-nephrin antibodies in rodent models, prompted us to hypothesize that nephrin autoantibodies may be present in patients with minimal change disease.

METHODS

We evaluated sera from patients with minimal change disease, enrolled in the Nephrotic Syndrome Study Network (NEPTUNE) cohort and from our own institutions, for circulating nephrin autoantibodies by indirect ELISA and by immunoprecipitation of full-length nephrin from human glomerular extract or a recombinant purified extracellular domain of human nephrin. We also evaluated renal biopsies from our institutions for podocyte-associated punctate IgG colocalizing with nephrin by immunofluorescence.

RESULTS

In two independent patient cohorts, we identified circulating nephrin autoantibodies during active disease that were significantly reduced or absent during treatment response in a subset of patients with minimal change disease. We correlated the presence of these autoantibodies with podocyte-associated punctate IgG in renal biopsies from our institutions. We also identified a patient with steroid-dependent childhood minimal change disease that progressed to end stage kidney disease; she developed a massive post-transplant recurrence of proteinuria that was associated with high pretransplant circulating nephrin autoantibodies.

CONCLUSIONS

Our discovery of nephrin autoantibodies in a subset of adults and children with minimal change disease aligns with published animal studies and provides further support for an autoimmune etiology. We propose a new molecular classification of nephrin autoantibody minimal change disease to serve as a framework for instigation of precision therapeutics for these patients.

De novo Glomerular Disease and the Significance of Electron Microscopy in Renal Transplantation

Background

De novo glomerular diseases comprising those both common and unique to transplant may develop in the renal allograft leading to posttransplant proteinuria, hematuria, or allograft failure. Electron microscopy (EM) is a useful adjunct to the standard light and immunofluorescence microscopy for accurately diagnosing these diseases and subsequently aiding the clinician in initiating appropriate treatments.

Summary

De novo diseases are those new-onset diseases in renal transplantation that are unrelated to the original kidney disease in the recipient. They include virtually any primary or secondary glomerular, tubulointerstitial, or vascular diseases, ranging from subclinical to clinically overt, having acute, subacute, or chronic clinical presentations. This review focuses on common or significant, mainly glomerular, entities, with particular attention to the EM findings. The time of onset, stage, and severity of these diseases may often be modified by the current immunosuppressive protocols and other donor and recipient predisposing characteristics.

Key Messages

A renal allograft biopsy not only improves our understanding of the pathophysiology but also provides diagnostic accuracy prognostic information, and potential for reversibility. In some cases, the biopsy leads to detection of unsuspected or clinically asymptomatic de novo diseases in the setting of other concomitant rejection processes, infection, or toxicity, which can dictate appropriate therapy. Routine EM in transplant kidney biopsies is a valuable modality in recognizing fully developed or early/subtle features of evolving de novo diseases, often during the subclinical phases, in "for cause" or surveillance/protocol allograft biopsies.

Rare inherited kidney diseases: an evolving field in Nephrology

There are more than 150 different rare genetic kidney diseases. They can be classified according to diagnostic findings as (i) disorders of growth and structure, (ii) glomerular diseases, (iii) tubular, and (iv) metabolic diseases. In recent years, there has been a shift of paradigm in this field. Molecular testing has become more accessible, our understanding of the underlying pathophysiologic mechanisms of these diseases has evolved, and new therapeutic strategies have become more available. Therefore, the role of nephrologists has progressively shifted from a mere spectator to an active player, part of a multidisciplinary team in the diagnosis and treatment of these disorders. This article provides an overview of the recent advances in rare hereditary kidney disorders by discussing the genetic aspects, clinical manifestations, diagnostic, and therapeutic approaches of some of these disorders, named familial focal and segmental glomerulosclerosis, tuberous sclerosis complex, Fabry nephropathy, and MYH-9 related disorder.

Australia and New Zealand renal gene panel testing in routine clinical practice of 542 families

Genetic testing in nephrology clinical practice has moved rapidly from a rare specialized test to routine practice both in pediatric and adult nephrology. However, clear information pertaining to the likely outcome of testing is still missing. Here we describe the experience of the accredited Australia and New Zealand Renal Gene Panels clinical service, reporting on sequencing for 552 individuals from 542 families with suspected kidney disease in Australia and New Zealand. An increasing number of referrals have been processed since service inception with an overall diagnostic rate of 35%. The likelihood of identifying a causative variant varies according to both age at referral and gene panel. Although results from high throughput genetic testing have been primarily for diagnostic purposes, they will increasingly play an important role in directing treatment, genetic counseling, and family planning.

Management of congenital nephrotic syndrome: consensus recommendations of the ERKNet-ESPN Working Group

Congenital nephrotic syndrome (CNS) is a heterogeneous group of disorders characterized by nephrotic-range proteinuria, hypoalbuminaemia and oedema, which manifest in utero or during the first 3 months of life. The main cause of CNS is genetic defects in podocytes; however, it can also be caused, in rare cases, by congenital infections or maternal allo-immune disease. Management of CNS is very challenging because patients are prone to severe complications, such as haemodynamic compromise, infections, thromboses, impaired growth and kidney failure. In this consensus statement, experts from the European Reference Network for Kidney Diseases (ERKNet) and the European Society for Paediatric Nephrology (ESPN) summarize the current evidence and present recommendations for the management of CNS, including the use of renin-angiotensin system inhibitors, diuretics, anticoagulation and infection prophylaxis. Therapeutic management should be adapted to the clinical severity of the condition with the aim of maintaining intravascular euvolaemia and adequate nutrition, while preventing complications and preserving central and peripheral vessels. We do not recommend performing routine early nephrectomies but suggest that they are considered in patients with severe complications despite optimal conservative treatment, and before transplantation in patients with persisting nephrotic syndrome and/or a WT1-dominant pathogenic variant.

Autoimmunity in Focal Segmental Glomerulosclerosis: A Long-Standing Yet Elusive Association

Focal segmental glomerulosclerosis (FSGS) is a histological term that describes a pathologic renal entity affecting both adults and children, with a wide array of possible underlying etiologies. Podocyte damage with scarring, the hallmark of this condition, leads to altered permeability of the glomerular barrier, which may result in massive proteinuria and relentless renal function deterioration. A definite cause of focal segmental glomerulosclerosis can be confirmed in a minority of cases, while most forms have been traditionally labeled as primary or idiopathic. Despite this definition, increasing evidence indicates that primary forms are a heterogenous group rather than a single disease entity: several circulating factors that may affect glomerular permeability have been proposed as potential culprits, and both humoral and cellular immunity have been implicated in the pathogenesis of the disease. Consistently, immunosuppressive drugs are considered as the cornerstone of treatment for primary focal segmental glomerulosclerosis, but response to these agents and long-term outcomes are highly variable. In this review we provide a summary of historical and recent advances on the pathogenesis of primary focal segmental glomerulosclerosis, focusing on implications for its differential diagnosis and treatment.

Bilateral Vesicoureteral Reflux in Congenital Nephrotic Syndrome

: Congenital nephrotic syndrome (CNS) is a rare genetic kidney disorder. Different associations between CNS and other organ anomalies have been reported previously. However, urologic abnormalities are not common. This case report can show the association of CNS as a genetic disorder with other abnormalities with a genetic basis. However, the association with urinary abnormalities is rare. We have reported a 25-day-old male newborn, who was referred to our hospital with generalized edema. During the initial evaluation, CNS was diagnosed. The baby, then four months old, was admitted to the hospital with high fever and poor feeding, and a diagnosis of febrile urinary tract infection was made. A voiding cystouretrography was performed that revealed bilateral high-grade vesicoureteral reflux. According to our findings in this case and the genetic basis of CNS and urinary tract anomalies, we recommend the investigation of the urinary tract in CNS patients if indicated.

A new mouse model of anti-GBM disease sheds light on maternal transfer of alloantibodies in glomerular disease

Membranous nephropathy and anti-glomerular basement membrane glomerulonephritis are characterized by the deposition of antibodies that recognize specific glomerular epitopes. These antibodies may develop in autoimmune diseases, after exposure to new antigens or after passive maternal transfer, such as in neonatal membranous nephropathy secondary to in utero transfer of anti-neutral endopeptidase protein Igs. In this issue of Kidney International, Abrahamson et al. reported a murine model of passive anti-glomerular basement membrane disease caused by antibody transfer from pregnant mice to their offspring.

Protein misfolding in endoplasmic reticulum stress with applications to renal diseases

Protein misfolding may be the result of a variety of different processes that disrupt the ability of a protein to form a thermodynamically stable tertiary structure that allows it to perform its proper function. In this chapter, we explore the nature of a protein's form that allows it to have a stable tertiary structure, and examine specific mutation that are known to occur in the coding regions of DNA that disrupt a protein's ability to be folded into a thermodynamically stable tertiary structure. We examine the consequences of these protein misfoldings in terms of the endoplasmic reticulum stress response and resulting unfolded protein response. These conditions are specifically related to renal diseases. Further, we explore novel therapeutics, pharmacological chaperones, that are being developed to alleviate the disease burden associated with protein misfolding caused by mutations. These interventions aim to stabilize protein folding intermediates and allow proper folding to occur as well as prevent protein aggregation and the resulting pathophysiological consequences.

Mouse Models of Congenital Kidney Anomalies

Congenital anomalies of the kidney and urinary tract (CAKUT) are common birth defects, which cause the majority of chronic kidney diseases in children. CAKUT covers a wide range of malformations that derive from deficiencies in embryonic kidney and lower urinary tract development, including renal aplasia, hypodysplasia, hypoplasia, ectopia, and different forms of ureter abnormalities. The majority of the genetic causes of CAKUT remain unknown. Research on mutant mice has identified multiple genes that critically regulate renal differentiation. The data generated from this research have served as an excellent resource to identify the genetic bases of human kidney defects and have led to significantly improved diagnostics. Furthermore, genetic data from human CAKUT studies have also revealed novel genes regulating kidney differentiation.

Diagnostic and Management Challenges in Congenital Nephrotic Syndrome

Congenital Nephrotic Syndrome (CNS) is defined as nephrotic range proteinuria, hypoalbuminaemia and edema in the first three months of life. CNS is most commonly genetic in cause, with international variance in the incidence of causative mutations. Initially defined by the histopathological appearance, increasingly sophisticated and accessible genetic analyses now provide a body of evidence to suggest that there is a disparity between the histological appearance, the genotype of individuals and the severity of the clinical disease. Through the evolution of management approaches CNS has changed from being an invariably fatal condition to one with appreciable ongoing morbidity and mortality but comparably good outcomes to other causes of paediatric end-stage renal disease, especially following transplantation. This review briefly summarises the more commonly recognised genetic mutations leading to CNS, addresses common management decisions, and concludes with potential therapies for the future.

The Role of p.Ser1105Ser (in NPHS1 Gene) and p.Arg548Leu (in PLCE1 Gene) with Disease Status of Vietnamese Patients with Congenital Nephrotic Syndrome: Benign or Pathogenic?

Background and Objectives: Congenital nephrotic syndrome (CNS), a genetic disease caused by mutations in genes on autosomes, usually occurs in the first three months after birth. A number of genetic mutations in genes, which encode for the components of the glomerular filtration barrier have been identified. We investigated mutations in NPHS1, NPHS2, PLCE1 (NPHS3), and WT1 genes that relate to the disease in Vietnamese patients. Materials and Methods: We performed genetic analysis of two unrelated patients, who were diagnosed with CNS in the Vietnam National Children’s Hospital with different disease status. The entire coding region and adjacent splice sites of these genes were amplified and sequenced using the Sanger method. The sequencing data were analyzed and compared with the NPHS1, NPHS2, PLCE1, and WT1 gene sequences published in Ensembl (ENSG00000161270, ENSG00000116218, ENSG00000138193, and ENSG00000184937, respectively) using BioEdit software to detect mutations. Results: We detected a new variant p.Ser607Arg and two other (p.Glu117Lys and p.Ser1105Ser) in the NPHS1 gene, as well as two variants (p.Arg548Leu, p.Pro1575Arg) in the PLCE1 gene. No mutations were detected in the NPHS2 and WT1 genes. Patient 1, who presented a heterozygous genotype of p.Ser1105Ser and p.Arg548Leu had a mild disease status but patient 2, who presented a homozygous genotype of these alleles, had a severe phenotype. Conclusions: These results suggest that variants p.Ser1105Ser (in NPHS1 gene) and p.Arg548Leu (in PLCE1 gene) in the homozygous form might play a role in the development of the disease in patients.

Non-immunologic allograft loss in pediatric kidney transplant recipients

Non-immunologic risk factors are a major obstacle to realizing long-term improvements in kidney allograft survival. A standardized approach to assess donor quality has recently been introduced with the new kidney allocation system in the USA. Delayed graft function and surgical complications are important risk factors for both short- and long-term graft loss. Disease recurrence in the allograft remains a major cause of graft loss in those who fail to respond to therapy. Complications of over immunosuppression including opportunistic infections and malignancy continue to limit graft survival. Alternative immunosuppression strategies are under investigation to limit calcineurin inhibitor toxicity. Finally, recent studies have confirmed long-standing observations of the significant negative impact of a high-risk age window in late adolescence and young adulthood on long-term allograft survival.

Whole-Exome Sequencing Enables a Precision Medicine Approach for Kidney Transplant Recipients

BACKGROUND

Whole-exome sequencing (WES) finds a CKD-related mutation in approximately 20% of patients presenting with CKD before 25 years of age. Although provision of a molecular diagnosis could have important implications for clinical management, evidence is lacking on the diagnostic yield and clinical utility of WES for pediatric renal transplant recipients.

METHODS

To determine the diagnostic yield of WES in pediatric kidney transplant recipients, we recruited 104 patients who had received a transplant at Boston Children's Hospital from 2007 through 2017, performed WES, and analyzed results for likely deleterious variants in approximately 400 genes known to cause CKD.

RESULTS

By WES, we identified a genetic cause of CKD in 34 out of 104 (32.7%) transplant recipients. The likelihood of detecting a molecular genetic diagnosis was highest for patients with urinary stone disease (three out of three individuals), followed by renal cystic ciliopathies (seven out of nine individuals), steroid-resistant nephrotic syndrome (nine out of 21 individuals), congenital anomalies of the kidney and urinary tract (ten out of 55 individuals), and chronic glomerulonephritis (one out of seven individuals). WES also yielded a molecular diagnosis for four out of nine individuals with ESRD of unknown etiology. The WES-related molecular genetic diagnosis had implications for clinical care for five patients.

CONCLUSIONS

Nearly one third of pediatric renal transplant recipients had a genetic cause of their kidney disease identified by WES. Knowledge of this genetic information can help guide management of both transplant patients and potential living related donors.

First Report of Recurrent Nephrotic Syndrome After Kidney Transplantation in a Patient With NUP93 Gene Mutations: A Case Report

Mutations in nucleoporin 93 (NUP93) gene have been shown recently to be one of the very rare causes of genetic steroid-resistant nephrotic syndrome (SRNS). Until now, none of the 7 published cases with NUP93-SRNS, experienced recurrence of nephrotic syndrome (NS) after transplantation. Here, we present the first case of recurrent NS in a patient with NUP93-SRNS ever reported. A 3-year-old boy with infantile SRNS was started on chronic peritoneal dialysis because of end-stage renal failure owing to biopsy-proven focal segmental glomerulosclerosis (FSGS). At the age of 6 years, the boy received a renal allograft. The posttransplant period was uncomplicated until 1.7 years after transplantation, when the patient developed nephrotic proteinuria during a respiratory tract infection. Renal graft biopsy showed subtotal fusion of podocytes, which was compatible with an early histopathologic sign of recurrence of FSGS. Immediate treatment with daily plasma exchange (PE) was started at the second day. The proteinuria disappeared completely after the second PE. However, it reappeared after stopping daily PE. It disappeared again after reintroduction of daily PE, therefore PE-dependent recurrent NS was diagnosed and treatment with rituximab was given. After the first dose, proteinuria never reappeared despite stopping PE therapy. Surprisingly, next-generation sequencing revealed compound heterozygous mutations in exons 16 and 18 of the NUP93 gene (c.1772G>T - European founder allele and 1916T>C) and his parents confirmed heterozygous asymptomatic carriers. This is the first case of recurrent NS in a patient with NUP93 gene mutations, suggesting a new pathomechanism possibly involving the nucleoporins.

Genomic medicine for kidney disease

Technologies such as next-generation sequencing and chromosomal microarray have advanced the understanding of the molecular pathogenesis of a variety of renal disorders. Genetic findings are increasingly used to inform the clinical management of many nephropathies, enabling targeted disease surveillance, choice of therapy, and family counselling. Genetic analysis has excellent diagnostic utility in paediatric nephrology, as illustrated by sequencing studies of patients with congenital anomalies of the kidney and urinary tract and steroid-resistant nephrotic syndrome. Although additional investigation is needed, pilot studies suggest that genetic testing can also provide similar diagnostic insight among adult patients. Reaching a genetic diagnosis first involves choosing the appropriate testing modality, as guided by the clinical presentation of the patient and the number of potential genes associated with the suspected nephropathy. Genome-wide sequencing increases diagnostic sensitivity relative to targeted panels, but holds the challenges of identifying causal variants in the vast amount of data generated and interpreting secondary findings. In order to realize the promise of genomic medicine for kidney disease, many technical, logistical, and ethical questions that accompany the implementation of genetic testing in nephrology must be addressed. The creation of evidence-based guidelines for the utilization and implementation of genetic testing in nephrology will help to translate genetic knowledge into improved clinical outcomes for patients with kidney disease.

Kidney transplantation in a child with Pierson syndrome

Congenital nephrotic syndrome is commonly associated with mutations in genes that encode podocyte and slit diaphragm proteins or the structural and regulatory proteins of the GBM. These mutations lead to the formation of dysfunctional proteins, which account for the resistance of the renal manifestations to conventional treatment methods. Consequently, patients become renal replacement therapy dependent. Mutation of the LAMB2 gene is associated with Pierson syndrome, which is an autosomal recessive disorder characterized by congenital nephrotic syndrome and ocular abnormalities. In this report, a 2-year-old male patient who was diagnosed with Pierson syndrome is presented. He had bilateral microcoria and developmental delay in addition to nephrotic syndrome. His renal function deteriorated rapidly, and he underwent a deceased donor kidney transplantation. He showed dramatic improvement after kidney transplantation; in addition to having good renal function, he started to catch up to his peers in terms of growth. Pierson syndrome should be considered during the diagnostic investigations of children with renal manifestations and ocular abnormalities. Children with Pierson syndrome must be evaluated in terms of kidney transplantation as soon as they are diagnosed.

Long-term outcome of congenital nephrotic syndrome after kidney transplantation in Japan

BACKGROUND

Congenital nephrotic syndrome is difficult to manage, particularly the Finnish type (CNF), with patients experiencing severe edema, sepsis and thrombosis before kidney transplantation. Further, nephrosis and thrombosis remain problematic after transplantation.

METHODS

Of 22 CNF patients managed at our hospital, 14 who underwent kidney transplantation were retrospectively studied. CNF was diagnosed according to standard criteria.

RESULTS

The study population consisted of 3 males and 11 females. Mean gestation period was 36 ± 1.4 weeks and mean birth weight was 2442 ± 454 g (mean placenta to body weight ratio: 0.4). All patients started dialysis at 2.4 ± 1.3 years and underwent kidney transplantation at 5.2 ± 2.0 years. The kidneys were donated by the parents (n = 13), and cadaver (n = 2), including overlap. Mean follow-up period after transplantation was 14.3 ± 8.9 years, and mean age at last observation was 19.5 ± 8.5 years. Two patients had recurrent proteinuria after kidney transplantation; one underwent retransplantation following graft failure and eventually required dialysis, while the second had complete remission after intensive immunosuppressive therapy. There were no cases of thrombosis or serious infections. Mean eGFR at the time of last observation was 57.3 ± 16.5 ml/min/1.73 m², while mean height SD score was - 2.1 ± 0.9 at the time of transplantation and - 1.5 ± 1.5 at last observation.

CONCLUSIONS

Long-term outcome in these 14 CNF patients showed satisfactory graft survival, improved height SD score, and favorable development. Although recurrent proteinuria after transplant was not predictive, it was associated with graft survival rate.

Application of next-generation sequencing technology to diagnosis and treatment of focal segmental glomerulosclerosis

A broad range of genetic and non-genetic factors can lead to kidney injury that manifests as focal segmental glomerulosclerosis (FSGS), which can be classified into primary (idiopathic) and secondary forms. Previous genetic approaches to familial or sporadic cases of FSGS or steroid-resistant nephrotic syndrome identified causal mutations in a subset of genes. Recently, next-generation sequencing (NGS) approaches are becoming a part of a standard assessment in medical genetics. Current knowledge of the comprehensive genomic information is changing the way we think about FSGS and draws attention not only to identification of novel causal genes, but also to potential roles for combinations of mutations in multiple genes, mutations with complex inheritance, and susceptibility genes with variable penetrance carrying relatively minor but significant effects. This review provides an update on recent advances in the genetic analysis of FSGS and highlights the potential as well as the new challenges of NGS for diagnosis and mechanism-based treatment of FSGS.

Replicated evidence for aminoacylase 3 and nephrin gene variations to predict antihypertensive drug responses

Aim: To replicate the genome-wide associations of the antihypertensive effects of bisoprolol and losartan in GENRES, using the Finnish patients of LIFE study. Patients & methods: We analyzed association of four SNPs with atenolol and three SNPs with losartan response in 927 Finnish LIFE patients (467 for atenolol and 460 for losartan). Results: rs2514036, a variation at a transcription start site of ACY3, was associated with blood pressure response to atenolol in men in LIFE. Response to bisoprolol was correlated to baseline plasma levels of N-acetylphenylalanine and phenylalanine (ACY3 substrate and end product, respectively) in GENRES study. NPHS1 variation rs3814995 was associated with losartan effect in LIFE. Conclusion: We provide support for two pharmacogenomic markers for beta-blockers and angiotensin receptor antagonists.

Kidney retransplantation in children following rejection and recurrent disease

Retransplantation accounts for approximately 15 % of the annual transplants performed in the USA, and in the recent International Collaborative Transplant Study report on pediatric patients 15.2 % of the 9209 patients included in the report were retransplant recipients. Although the significant advances in clinical management and newer immunosuppressive agents have had a significant impact on improving short-term allograft function, it is apparent that long-term allograft function remains suboptimal. Therefore, it is likely that the majority of pediatric renal allograft recipients will require one or more retransplants during their lifetime. Unfortunately, a second or subsequent graft in pediatric recipients has inferior long-term graft survival rates compared to initial grafts, with decreasing rates with each subsequent graft. Multiple issues influence the outcome of retransplantation, with the most significant being the cause of the prior transplant failure. Non-adherence-associated graft loss poses unresolved ethical issues that may impact access to retransplantation. Graft nephrectomy prior to retransplantation may benefit selected patients, but the impact of an in situ failed graft on the development of panel-reactive antibodies remains to be definitively determined. It is important that these and other factors discussed in this review be taken into consideration during the counseling of families on the optimal approach for their child who requires a retransplant.

Rituximab is not a "magic drug" in post-transplant recurrence of nephrotic syndrome

Pediatric patients with end-stage renal failure due to severe drug-resistant nephrotic syndrome are at risk of rapid recurrence after renal transplantation. Treatment options include plasmapheresis, high-dose of cyclosporine A/methylprednisolone and more recently-rituximab (anti-B CD20 monoclonal depleting antibody). We report five patients with immediate (1-2 days) post-transplant recurrence of nephrotic syndrome, treated with this kind of combined therapy including 2-4 weekly doses of 375 mg/m(2) of rituximab. Only two (of five) patients have showed full long-term remission, while the partial remission was seen in two cases, and no clinical effect at all was achieved in one patient. The correlation between B CD19 cells depletion and clinical effect was present in two cases only. Severe adverse events were present in two patients, including one fatal rituximab-related acute lung injury.

CONCLUSION

The anti-CD20 monoclonal antibody may be not effective in all pediatric cases of rapid post-transplant recurrence of nephrotic syndrome, and benefit/risk ratio must be carefully balanced on individual basis before taking the decision to use this protocol.

WHAT IS KNOWN

• nephrotic syndrome may recur immediately after renal transplantation • plasmapheresis combined with pharmacotherapy is used as rescue management • rituximab was reported as effective drug both in primary and post-transplant nephrotic syndrome What is New: • rituximab may not be effective is several cases of post-transplant nephrotic syndrome due to variety of underlying mechanisms of the disease, which may be or not be responsive to this drug • there may be no correlation between drug-induced depletion of specific B cells and clinical effect; this might suggest B-cell independent manner of rituximab action.

The second report of the Nordic Pediatric Renal Transplantation Registry 1997-2012: More infant recipients and improved graft survivals

The NPRTSG has collected data on pediatric KTx since 1994. The registry archives information from all centers that perform pediatric KTx in Denmark, Finland, Norway, and Sweden and has 100% coverage. The first NPRTSG report was published in 1998 and was based on data collected in the 1982─1996 period. The present report provides data on 602 pediatric KTx in the Nordic countries from 1997 to 2012. Comparison of the patient demographics and one- and three-yr graft survivals between the two time cohorts revealed no significant change in the recipient and donor demographics. The number of transplantations increased by approximately 30%, doubling the recipients below the age of two yr. The use of Tac and mycophenolate as primary immunosuppression increased from practically 0% to 50% and 40%, respectively. The one- and three-yr graft survivals improved significantly (p < 0.001), especially among the youngest recipients with transplant from DD. In these patients, the one-yr survival improved from 70% to 94.6% and the three-yr graft survival from 60% to 94.6%, respectively. The improved graft survival may be at least partly due to changes in immunosuppression strategies, but also greater experience may also be of importance.

The amino acid mutations of the podocin in proteinuria: a meta-analysis

While many previous studies have reported an association between the single-nucleotide polymorphisms (SNPs) of the podocin and proteinuria occurred, a conclusive relationship has not been defined in every oligoallelic state of amino acid (AA) mutations in podocin. In this study, we performed a meta-analysis of the published data to investigate the impact of the oligoallelic AA mutations of the podocin on proteinuria; a total 16 AA mutations were investigated for oligoallelic pathogenicity. Despite significant heterogeneity within some of the comparisons, the results revealed significantly higher risks of proteinuria in early-onset (onset age <16) individuals for five mutations (P118L, R138Q, R168H, V180M, and V260E), and in all onset ages individuals for five mutations (R138Q, G140X, R229Q, V260E, and V290M) compared to non-variant individuals. We also tested the steroid response in individuals with R229Q and E237Q. No statistically significant differences in the two mutations carrier rate were observed between steroid resistance patients and controls. No AA mutation was selected for meta-analysis on the recurrence of proteinuria after renal transplantation as lack of control data. In conclusion, our meta-analysis tested the pathogenicity of the oligoallelic AA mutations in podocin and suggested the potential causative mutations, and the alleles showing an association with protein susceptibility. The sensitivity and specificity of each causative mutation are pending further testing.

Primary disease recurrence—effects on paediatric renal transplantation outcomes

Primary disease recurrence after renal transplantation is mainly diagnosed by examination of biopsy samples, but can also be associated with clinical symptoms. In some patients, recurrence can lead to graft loss (7-8% of all graft losses). Primary disease recurrence is generally associated with a high risk of graft loss in patients with focal segmental glomerulosclerosis, membranous proliferative glomerulonephritis, primary hyperoxaluria or atypical haemolytic uraemic syndrome. By contrast, disease recurrence is associated with a limited risk of graft loss in patients with IgA nephropathy, renal involvement associated with Henoch-Schönlein purpura, antineutrophil cytoplasmic antibody-associated glomerulonephritis or lupus nephritis. The presence of systemic diseases that affect the kidneys, such as sickle cell anaemia and diabetes mellitus, also increases the risk of delayed graft loss. This Review provides an overview of the epidemiology, pathophysiology and management of primary disease recurrence in paediatric renal graft recipients, and describes the overall effect on graft survival of each of the primary diseases listed above. With appropriate management, few paediatric patients should be excluded from renal transplantation programmes because of an increased risk of recurrence.