Monogenic Steroid-resistant Nephrotic Syndrome Research Articles

#3670 THE ROLE OF CALCINEURIN INHIBITORS IN MONOGENIC PEDIATRIC STEROID RESISTANT NEPHROTIC SYNDROME: A RETROSPECTIVE, MULTICENTER STUDY

Abstract Background and Aims Response to calcineurin inhibitors (CNI) is associated with a significant improvement in long-term kidney survival of children with non-genetic steroid resistant nephrotic syndrome (SRNS). On the contrary, these agents are considered non-efficacious in monogenic SRNS and are contraindicated according to the latest International Pediatric Nephrology Association (IPNA) Clinical Practice Recommendations for SRNS. However, there is evidence suggesting that remission with CNI therapy in this subgroup of children with SRNS is possible, but no studies to date have assessed this question in a systematic way. We aimed to study the incidence of response to CNI in children with monogenic SRNS, factors predictive of remission and the effect of treatment on kidney survival. Method Retrospective cohort study of children 0–18 years with genetically confirmed SRNS treated with a CNI for at least 3 months. Demographic, clinical, genetic, biochemical, histopathologic and treatment data were collected at various time points; at clinical diagnosis, 6, 12, 24 months from CNI onset, and last available follow-up. Pathogenicity of all reported variants was assessed by a dedicated geneticist according to the American College of Medical Genetics guidelines and only patients with a pathogenic genotype were included in the analysis[1]. Patients were classified according to their response to CNI as complete, partial or non-responders based on the IPNA Clinical Practice Recommendations for SRNS[2]. Results 141 patients from 37 international paediatric nephrology centers were included in the study. At 6 months from CNI initiation and at last visit, 27.6% and 22.5%, respectively, demonstrated either complete or partial response (“at least partial response”). Median observation time between CNI initiation and last visit was 42.1 months (IQR 20.1–65.6) and was comparable between patients with no response and at least partial response (42.3 vs 41.6 months; P>0.05). No serious adverse effects mandating treatment discontinuation were reported. Children demonstrating at least partial response at 6 months had a lower risk of progression to kidney failure at last visit versus non-responders (hazard ratio [95%CI] 0.25, [0.10–0.62]; P = 0.003). Subgroup analysis of patients with a follow-up of at least 2 years revealed similar results with a hazard ratio of 0.35 (95%CI 0.14–0.91; P = 0.03). Of the various clinical, biochemical, genetic, histopathologic and treatment parameters tested in a multivariable logistic regression model only higher serum albumin at CNI onset was associated with higher likelihood of response at 6 months (odds ratio [95% CI] 1.16, [1.08–1.24]; P < 0.001). Conclusion Our findings suggest that CNI use could be considered in monogenic SRNS and that achievement of response in this setting can alter an otherwise dismal long-term kidney outcome.

The case for treatment of monogenic SRNS with calcineurin inhibitors

Currently, no evidence-based guidelines exist for treatment of children with monogenic steroid-resistant nephrotic syndrome. A retrospective study on 141 patients from Malakasioti etal. revealed that 27.6% responded to calcineurin inhibitor (CNI) treatment, and 75% of responders maintained stable kidney function. Virtually all CNI nonresponders developed progressive loss of kidney function. This study emphasized roles for CNIs in patients with monogenic steroid-resistant nephrotic syndrome, and the need for future studies to identify CNI response biomarkers.

A multicenter retrospective study of calcineurin inhibitors in nephrotic syndrome secondary to podocyte gene variants

While 44-83% of children with steroid-resistant nephrotic syndrome (SRNS) without a proven genetic cause respond to treatment with a calcineurin inhibitor (CNI), current guidelines recommend against the use of immunosuppression in monogenic SRNS. This is despite existing evidence suggesting that remission with CNI treatment is possible and can improve prognosis in some cases of monogenic SRNS. Herein, our retrospective study assessed response frequency, predictors of response and kidney function outcomes among children with monogenic SRNS treated with a CNI for at least three months. Data from 203 cases (age 0-18 years) were collected from 37 pediatric nephrology centers. Variant pathogenicity was reviewed by a geneticist, and 122 patients with a pathogenic and 19 with a possible pathogenic genotype were included in the analysis. After six months of treatment and at last visit, 27.6% and 22.5% of all patients respectively, demonstrated partial or full response. Achievement of at least partial response at six months of treatment conferred a significant reduction in kidney failure risk at last follow-up compared to no response (hazard ratio [95% confidence interval] 0.25, [0.10-0.62]). Moreover, risk of kidney failure was significantly lower when only those with a follow-up longer than two years were considered (hazard ratio 0.35, [0.14-0.91]). Higher serum albumin level at CNI initiation was the only factor related to increased likelihood of significant remission at six months (odds ratio [95% confidence interval] 1.16, [1.08-1.24]). Thus, our findings justify a treatment trial with a CNI also in children with monogenic SRNS.

Shared genetic risk across different presentations of gene test–negative idiopathic nephrotic syndrome

BackgroundIdiopathic nephrotic syndrome (INS) is classified in children according to response to initial corticosteroid therapy into steroid-sensitive (SSNS) and steroid-resistant nephrotic syndrome (SRNS), and in adults according to histology into minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). However, there is well-recognised phenotypic overlap between these entities. Genome-wide association studies (GWAS) have shown a strong association between SSNS and variation at HLA, suggesting an underlying immunological basis. We sought to determine whether a risk score generated from genetic variants associated with SSNS could be used to gain insight into the pathophysiology of INS presenting in other ways.MethodsWe developed an SSNS genetic risk score (SSNS-GRS) from the five variants independently associated with childhood SSNS in a previous European GWAS. We quantified SSNS-GRS in independent cohorts of European individuals with childhood SSNS, non-monogenic SRNS, MCD, and FSGS, and contrasted them with SSNS-GRS quantified in individuals with monogenic SRNS, membranous nephropathy (a different immune-mediated disease-causing nephrotic syndrome), and healthy controls.ResultsThe SSNS-GRS was significantly elevated in cohorts with SSNS, non-monogenic SRNS, MCD, and FSGS compared to healthy participants and those with membranous nephropathy. The SSNS-GRS in all cohorts with non-monogenic INS were also significantly elevated compared to those with monogenic SRNS.ConclusionsThe shared genetic risk factors among patients with different presentations of INS strongly suggests a shared autoimmune pathogenesis when monogenic causes are excluded. Use of the SSNS-GRS, in addition to testing for monogenic causes, may help to classify patients presenting with INS.Graphical abstractA higher resolution version of the Graphical abstract is available as Supplementary information

The Clinical and Genetic Features in Chinese Children With Steroid-Resistant or Early-Onset Nephrotic Syndrome: A Multicenter Cohort Study.

Steroid-resistant nephrotic syndrome (SRNS) is one of the major causes of end-stage kidney disease (ESKD) in children and young adults. For approximately 30% of children with SRNS results from a genetic cause. In this study, genotype-phenotype correlations in a cohort of 283 pediatric patients with SRNS or early-onset NS (nephrotic syndrome presenting within the first year of life) from 23 major pediatric nephrology centers in China were analyzed. All patients were performed with next-generation sequencing and Sanger sequencing. The overall mutation detection rate was 37.5% (106 of 283 patients). WT1 was the most frequently detected mutation, followed by NPHS1, NPHS2, and ADCK4, and these four major causative genes (WT1, NPHS1, NPHS2, and ADCK4) account for 73.6% of patients with monogenic SRNS. Thirteen of 106 individuals (12.3%) carried mutations in ADCK4 that function within the coenzyme Q10 biosynthesis pathway. In the higher frequently ADCK4-related SRNS, two mutations, c.737G>A (p.S246N) and c.748G>C (p.D250H), were the most prevalent. Our study provides not only definitive diagnosis but also facilitate available targeted treatment for SRNS, and prediction of prognosis and renal outcome. Our indications for genetic testing are patients with FSGS, initial SRNS, cases of positive family history or those with extra-renal manifestations.

High Incidence of COL4A Genetic Variants Among a Cohort of Children With Steroid-Resistant Nephrotic Syndrome From Eastern India

High Incidence of COL4A Genetic Variants Among a Cohort of Children With Steroid-Resistant Nephrotic Syndrome From Eastern India

MO1027EFFICACY OF CALCINEURIN INHIBITORS IN CHILDREN WITH MONOGENIC STEROID-RESISTANT NEPHROTIC SYNDROME

Abstract Background and Aims Monogenic causes of steroid-resistant nephrotic syndrome (SRNS) have been reported for up to one-third of children depending on age of the disease onset. Immunosuppressive treatment of genetic SRNS with calcineurin inhibitors (CNIs) is still controversial. The aim of the study was to investigate the efficacy of CNIs with focus on inducing remission and long-term kidney function in children with monogenic SRNS. Method Retrospective analysis of efficacy CNIs in five children (2M/3F) with monogenic SRNS was performed. Kidney biopsy prior CNIs revealed FSGS (n=4) and MCD (n=1). The initial cyclosporine (CsA) dose was 5 mg/kg/24h to keep a target level of 80-150 ng/ml and tacrolimus (TAC) - 0.1 mg/kg/24h to achieve a target level of 5-10 ng/ml. CsA took all 5 patients with subsequent switching to TAC in 2 children due to cosmetic side effects. The median follow-up period was 165.0 (IQR: 59.0; 185.5) months. Next generation sequencing (NGS) was used for identification of pathogenic variants in all patients. Results The median age at onset of monogenic SRNS was 33.0 (IQR: 16.5; 63.0) months. 2/5 (40%) patients presented with acute SRNS, 1/5 (20%) child with infantile NS, 1/5 (20%) - with isolated nephrotic range proteinuria with hypoalbuminemia and 1/5 (20%) - with NS and extrarenal features of Nail-Patella syndrome. NGS identified previously described pathogenic variants in all 5 children, including NPHS2 homozygous c.28dup (p.Glu87Ter) (n=1), NPHS2 compound heterozygous c.868G>A (p.Val290Met) in combination with c.686G>A (p.Arg229Gln) (n=1), LMX1B heterozygous c.788T>G (p.Val263Gly) (n=1), LMX1B heterozygous c.737G>A (p.Arg246Gln) (n=1), and COL4A3 heterozygous c.2962G>A (p.Gly988Arg) variant (n=1). The median time from diagnosis to initiation of CNIs treatment was 72.0 (IQR: 33.0; 93.0) months. CNIs induced complete remission in 2/5 (40%) patients, presented with acute SRNS, including one girl with MCD due to NPHS2 compound heterozygous variants with mutation-dependent pathogenicity of one (p.R229Q) of them and one boy with FSGS due to COL4A3 heterozygous variant (n=1). Partial remission was induced by CNIs in 2/5 (40%) girls with FSGS due to LMX1B heterozygous variants with isolated SRNS (n=1) and Nail-Patella syndrome (n=1). The median duration of CNIs treatment to obtain complete or partial remission was 13.5 (IQR: 6.8; 15.8) months. Acute CNIs-associated nephrotoxicity had 2 patients with LMX1B variants. At the last follow up full and partial responders to CNIs treatment aged of 16.5 (IQR: 11.8; 17.5) years had CKD-1 (n=3) and CKD-2 (n=1). 1/5 (20%) boy with NPHS2-associated infantile NS was CNI resistant and developed CKD-5 at the age of 6.5 years with subsequent living related kidney transplantation. Conclusion We found that 4/5 (80%) children with monogenic SRNS demonstrated partial or full response to CNIs treatment with stable long-term kidney function. We assume that CNIs might improve podocyte function by stabilization of their cytoskeleton disrupted in patients with monogenic SRNS.

POS-458 PERSPECTIVES OF CALCINEURIN INHIBITORS TREATMENT IN HEREDITARY STEROID-RESISTANT NEPHROTIC SYNDROME

Therapy of steroid-resistant nephrotic syndrome (SRNS) remains an actual problem of pediatric nephrology despite the expansion of therapeutic options. It is considered that calcineurin inhibitors (CNIs) have limited efficacy for the majority of patients with SRNS especially in cases with confirmed genetic causes. We observed 136 children (66 - 48,5% males) from 58 regions of the Russian Federation with SRNS and/or hereditary NS who received CNI during 1 month - 7 years. The average age of our patients accounted for 11 y. 7 m. (SD 60,753 m.) The average age of manifestation was 4 y. 7 m. (SD 51,29 m.) Family history was positive in 13,2% (18 patients). Steroids were previously applied in 128 children (94,1%) with no remission achieved. Genetic testing by next-generation sequencing was performed in all patients. We detected pathogenic variants of genes associated with nephrotic syndrome and its phenotypic copies in 71 patients (52,2%).CNI inefficiency was observed in 82 children (60,3%): 44,6% in non-genetic and 74,6% of SRNS associated with pathogenic variants of podocyte genes. In idiopathic NS partial and complete remission had been achieved in an approximately equal percentage of cases - 29,2% (19) and 26,2% (17) children. In monogenic SRNS complete and partial remission was observed in 11,3% (8) and 14,1% (10) children respectively. Due to the small number of patients with different pathogenic variants, it is difficult to make any accurate conclusions. Three of ten WT1-associated SRNS had achieved partial remission.Twenty children - 14,7% (18 - genetic SRNS, 2 - non-genetic SRNS) - progressed to the end-stage renal disease during the observation period (2010-2020), 17 of them were transplanted (12,5%), recurrence of NS to the graft occurred in 5 patients (29,4%): with pathogenic variants in NPHS2, WT1, ARHGAP24, MYH9, and 1 child without any revealed genetic cause of SRNS.View Large Image Figure ViewerDownload Hi-res image Download (PPT) CNI treatment can be effective in children with SRNS in 39,8% of cases. Only 26,7% of genetic NS achieved complete or partial remission so CNI prescription can be effective but should not be used routinely. Moreover, the expectation for remission in genetic SRNS is meaningless after 3 months of treatment.

Response to First Course of Intensified Immunosuppression in Genetically Stratified Steroid Resistant Nephrotic Syndrome.

Intensified immunosuppression in steroid-resistant nephrotic syndrome is broadly applied, with disparate outcomes. This review of patients from the United Kingdom National Study of Nephrotic Syndrome cohort aimed to improve disease stratification by determining, in comprehensively genetically screened patients with steroid-resistant nephrotic syndrome, if there is an association between response to initial intensified immunosuppression and disease progression and/or post-transplant recurrence. Pediatric patients with steroid-resistant nephrotic syndrome were recruited via the UK National Registry of Rare Kidney Diseases. All patients were whole-genome sequenced, whole-exome sequenced, or steroid-resistant nephrotic syndrome gene-panel sequenced. Complete response or partial response within 6 months of starting intensified immunosuppression was ascertained using laboratory data. Response to intensified immunosuppression and outcomes were analyzed according to genetic testing results, pattern of steroid resistance, and first biopsy findings. Of 271 patients, 178 (92 males, median onset age 4.7 years) received intensified immunosuppression with response available. A total of 4% of patients with monogenic disease showed complete response, compared with 25% of genetic-testing-negative patients (P=0.02). None of the former recurred post-transplantation. In genetic-testing-negative patients, 97% with complete response to first intensified immunosuppression did not progress, whereas 44% of nonresponders developed kidney failure with 73% recurrence post-transplant. Secondary steroid resistance had a higher complete response rate than primary/presumed resistance (43% versus 23%; P=0.001). The highest complete response rate in secondary steroid resistance was to rituximab (64%). Biopsy results showed no correlation with intensified immunosuppression response or outcome. Patients with monogenic steroid-resistant nephrotic syndrome had a poor therapeutic response and no post-transplant recurrence. In genetic-testing-negative patients, there was an association between response to first intensified immunosuppression and long-term outcome. Patients with complete response rarely progressed to kidney failure, whereas nonresponders had poor kidney survival and a high post-transplant recurrence rate. Patients with secondary steroid resistance were more likely to respond, particularly to rituximab.

Genetic Testing for Steroid-Resistant-Nephrotic Syndrome in an Outbred Population.

Background: Steroid-resistant nephrotic syndrome (SRNS) is a leading cause of end-stage kidney disease in children and young adults. Despite advances in genomic science that have led to the discovery of >50 monogenic causes of SRNS, there are no clear guidelines for genetic testing in clinical practice.Methods: Using high throughput sequencing, we evaluated 492 individuals from 181 families for mutations in 40 known SRNS genes. Causative mutations were defined as missense, truncating, and obligatory splice site variants with a minor allele frequency <1% in controls. Non-synonymous variants were considered pathogenic if determined to be deleterious by at least two in silico models. We further evaluated for differences in age at disease onset, family history of SRNS or chronic kidney disease, race, sex, renal biopsy findings, and extra-renal manifestations in subgroups with and without disease causing variants.Results: We identified causative variants in 40 of 181 families (22.1%) with SRNS. Variants in INF2, COL4A3, and WT1 were the most common, accounting for over half of all causative variants. Causative variants were identified in 34 of 86 families (39.5%) with familial disease and 6 of 95 individuals (6.3%) with sporadic disease (χ2 p < 0.00001). Family history was the only significant clinical predictor of genetic SRNS.Conclusion: We identified causative mutations in almost 40% of all families with hereditary SRNS and 6% of individuals with sporadic disease, making family history the single most important clinical predictors of monogenic SRNS. We recommend genetic testing in all patients with SRNS and a positive family history, but only selective testing in those with sporadic disease.

Identification of genetic causes for sporadic steroid-resistant nephrotic syndrome in adults

Monogenic forms of Steroid-Resistant Nephrotic Syndrome (SRNS) have been widely characterized, but genetic screening paradigms preferentially address congenital, infantile onset, and familial cases. Our aim was to characterize the distribution of disease-causing gene mutations in adults with sporadic SRNS or focal segmental glomerulosclerosis (FSGS). We selected adult patients with non-syndromic, biopsy-proven FSGS or SRNS in the absence of known family history. Strict clinical criteria included lack of response to glucocorticoids and cyclosporine, and no recurrence after kidney transplantation. Mutations in SRNS genes were detected using a targeted gene panel. Sixteen of 135 tested participants (11.8%) carried pathogenic mutations in monogenic SRNS genes, and 14 others (10.4%) carried two APOL1 high-risk alleles. Autosomal recessive disease was diagnosed in 5 participants, autosomal dominant disease in 9, and X-linked disease in 2. Four participants carried a de novo heterozygous mutation. Among the 16 participants with identified mutations in monogenic SNRS genes, 7 (43.7%) had type IV collagen mutations. Mutations in monogenic SNRS genes were identified primarily in participants with proteinuria onset before 25 years of age, while the age at disease onset was variable in those with APOL1 high-risk genotype. Mean age at diagnosis was lower and renal survival was worse in participants with identified mutations in SNRS genes than in those without mutations. We found a significant rate of pathogenic mutations in adults with SRNS, with Type IV collagen mutations being the most frequent. These findings may have immediate impact on clinical practice.

Treatment of steroid-resistant nephrotic syndrome in the genomic era.

The pathogenesis of steroid-resistant nephrotic syndrome (SRNS) is not completely known. Recent advances in genomics have elucidated some of the molecular mechanisms and pathophysiology of the disease. More than 50 monogenic causes of SRNS have been identified; however, these genes are responsible for only a small fraction of SRNS in outbred populations. There are currently no guidelines for genetic testing in SRNS, but evidence from the literature suggests that testing should be guided by the genetic architecture of the disease in the population. Notably, most genetic forms of SRNS do not respond to current immunosuppressive therapies; however, a small subset of patients with monogenic SRNS will achieve partial or complete remission with specific immunomodulatory agents, presumably due to non-immunosuppressive effects of these agents. We suggest a pragmatic approach to the therapy of genetic SRNS, as there is no evidence-based algorithm for the management of the disease.

APOL1 risk genotype in European steroid-resistant nephrotic syndrome and/or focal segmental glomerulosclerosis patients of different African ancestries

Apolipoprotein L1 (APOL1) risk variants are strongly associated with sporadic focal segmental glomerulosclerosis (FSGS) in populations with African ancestry. We determined the frequency of G1/G2 variants in steroid-resistant nephrotic syndrome (SRNS)/FSGS patients with African or French West Indies ancestry in France and its relationships with other SRNS genes. In a cohort of 152 patients (139 families), the APOL1 risk variants were genotyped by direct Sanger sequencing and pathogenic mutations were screened by next-generation sequencing with a panel including 35 SRNS genes. The two risk allele [high-risk (HR)] genotypes were found in 43.1% (66/152) of subjects compared with 18.9% (106/562) in a control population (P < 0.0001): 33 patients homozygous for APOL1 G1 alleles, 4 homozygous for G2 and 29 compound heterozygous for G1 and G2. Compared with patients in the low-risk (LR) group, patients in the HR group were more likely to originate from the French West Indies than from Africa [45/66 (68.2%) versus 30/86 (34.9%); P < 0.0001]. There were more familial cases in the HR group [27 (41.5%) versus 8 (11.4%); P < 0.0001]. However, causative mutations in monogenic SRNS genes were found in only 1 patient in the HR group compared with 16 patients (14 families) in the LR group (P = 0.0006). At diagnosis, patients in the HR group without other mutations were more often adults [35 (53.8%) versus 19 (27.1%); P = 0.003] and had a lower estimated glomerular filtration rate (78.9 versus 98.8 mL/min/1.73 m2; P = 0.02). The HR genotype is frequent in FSGS patients with African ancestry in our cohort, especially in those originating from the West Indies, and confer a poor renal prognosis. It is usually not associated with other causative mutations in monogenic SRNS genes.

Use of genomic and functional analysis to characterize patients with steroid-resistant nephrotic syndrome

Children with genetic causes of steroid-resistant nephrotic syndrome (SRNS) usually do well after renal transplantation, while some with idiopathic SRNS show recurrence due to a putative podocyte-toxic factor. Distinguishing different forms of SRNS based on clinical criteria has been difficult. The aim of our study was to test a novel approach that allows categorization of patients into clinically useful subgroups. Seventeen patients with clinically confirmed SRNS were analyzed by next-generation sequencing (NGS) of 37 known SRNS genes and a functional assay of cultured human podocytes, which indirectly tests for toxicity of patients' sera by evidenced loss of podocyte focal adhesion complex (FAC) number. We identified a pathogenic mutation in seven patients (41%). Sera from patients with monogenic SRNS caused mild loss of FAC number down to 73% compared to untreated controls, while sera from seven of the remaining ten patients with idiopathic SRNS caused significant FAC number loss to 43% (non-overlapping difference 30%, 95% CI 26-36%, P< 0.001). All patients with recurrent SRNS (n= 4) in the graft showed absence of podocyte gene mutations but significant FAC loss. Three patients had no mutation nor serum podocyte toxicity. Our approach allowed categorization of patients into three subgroups: (1) patients with monogenic SRNS; (2) patients with idiopathic SRNS and marked serum podocyte toxicity; and (3) patients without identifiable genetic cause nor evidence of serum podocyte toxicity. Post-transplant SRNS recurrence risk appears to be low in groups 1 and 3, but high in group 2.

Genetic variants in the LAMA5 gene in pediatric nephrotic syndrome.

Nephrotic syndrome (NS), a chronic kidney disease, is characterized by significant loss of protein in the urine causing hypoalbuminemia and edema. In general, ∼15% of childhood-onset cases do not respond to steroid therapy and are classified as steroid-resistant NS (SRNS). In ∼30% of cases with SRNS, a causative mutation can be detected in one of 44 monogenic SRNS genes. The gene LAMA5 encodes laminin-α5, an essential component of the glomerular basement membrane. Mice with a hypomorphic mutation in the orthologous gene Lama5 develop proteinuria and hematuria. To identify additional monogenic causes of NS, we performed whole exome sequencing in 300 families with pediatric NS. In consanguineous families we applied homozygosity mapping to identify genomic candidate loci for the underlying recessive mutation. In three families, in whom mutations in known NS genes were excluded, but in whom a recessive, monogenic cause of NS was strongly suspected based on pedigree information, we identified homozygous variants of unknown significance (VUS) in the gene LAMA5. While all affected individuals had nonsyndromic NS with an early onset of disease, their clinical outcome and response to immunosuppressive therapy differed notably. We here identify recessive VUS in the gene LAMA5 in patients with partially treatment-responsive NS. More data will be needed to determine the impact of these VUS in disease management. However, familial occurrence of disease, data from genetic mapping and a mouse model that recapitulates the NS phenotypes suggest that these genetic variants may be inherited factors that contribute to the development of NS in pediatric patients.