Familial steroid-responsive nephrotic syndrome and HLA antigens in Bengali children

Association between HLA alleles and sub-phenotype of childhood steroid-sensitive nephrotic syndrome

BACKGROUND

Few studies have addressed the effects of human leukocyte antigen (HLA) alleles on different clinical sub-phenotypes in childhood steroid-sensitive nephrotic syndrome (SSNS), including SSNS without recurrence (SSNSWR) and steroid-dependent nephrotic syndrome/frequently relapse nephrotic syndrome (SDNS/FRNS). In this study, we investigated the relationship between HLA system and children with SSNSWR and SDNS/FRNS and clarified the value of HLA allele detection for precise typing of childhood SSNS.

METHODS

A total of 241 Chinese Han individuals with SSNS were genotyped using GenCap-WES Capture Kit, and four-digit resolution HLA alleles were imputed from available Genome Wide Association data. The distribution and carrying frequency of HLA alleles in SSNSWR and SDNS/FRNS were investigated. Additionally, logistic regression and mediating effects were used to examine the relationship between risk factors for disease process and HLA system.

RESULTS

Compared with SSNSWR, significantly decreased serum levels of complement 3 (C3) and complement 4 (C4) at onset were detected in SDNS/FRNS (C3, P < 0.001; C4, P = 0.018). The average time to remission after sufficient initial steroid treatment in SDNS/FRNS was significantly longer than that in SSNSWR (P = 0.0001). Low level of C4 was further identified as an independent risk factor for SDNS/FRNS (P = 0.008, odds ratio = 0.174, 95% confidence interval 0.048-0.630). The HLA-A*11:01 allele was independently associated with SSNSWR and SDNS/FRNS (P = 0.0012 and P = 0.0006, respectively). No significant HLA alleles were detected between SSNSWR and SDNS/FRNS. In addition, a mediating effect among HLA-I alleles (HLA-B*15:11, HLA-B*44:03 and HLA-C*07:06), C4 level and SDNS/FRNS was identified.

CONCLUSIONS

HLA-I alleles provide novel genetic markers for SSNSWR and SDNS/FRNS. HLA-I antigens may be involved in steroid dependent or frequent relapse in children with SSNS as mediators of immunoregulation.

HLA Loci and Recurrence of Focal Segmental Glomerulosclerosis in Pediatric Kidney Transplantation

Recurrent focal segmental glomerulosclerosis (FSGS) after kidney transplantation accounts for the majority of allograft failures in children with primary FSGS. Although current research focuses on FSGS pathophysiology, a common etiology and mechanisms of disease recurrence remain elusive.

GWAS-Based Discoveries in IgA Nephropathy, Membranous Nephropathy, and Steroid-Sensitive Nephrotic Syndrome

Over the past decade, genome-wide association studies (GWAS) have emerged as a powerful tool to understand the genetic basis of complex traits in humans. The GWAS approach has been successfully applied to primary glomerular disorders, providing numerous novel insights into the genetic architecture of IgA nephropathy, membranous nephropathy, and steroid-sensitive nephrotic syndrome. IgA nephropathy appears to have a highly complex polygenic architecture, with nearly 20 genome-wide significant loci of small-to-moderate effects discovered to date. In contrast, the genetic susceptibility to membranous nephropathy and steroid-sensitive nephrotic syndrome appears to be driven by a small number of large-effect loci. The MHC locus on chromosome 6p21 is strongly associated with genetic susceptibility to all major types of immune-mediated glomerulopathies. However, a distinct set of classical HLA alleles is associated with each individual disease type, pinpointing to specific immune mechanisms underlying each of these conditions. Additional insights from the discovery of non-HLA risk loci reinforced the role of innate and adaptive immunity in the pathogenesis of these disorders, and highlighted important susceptibility overlaps between glomerular and other autoimmune and inflammatory conditions. Despite these initial successes, much larger GWAS and sequencing studies are still needed for each individual glomerular disease type. Increased power will be critical to comprehensively test for genetic effects across the full spectrum of allelic frequencies, to detect gene-gene and gene-environment interactions, and to potentially improve the performance of polygenic risk predictors. Moreover, the existing studies are limited mostly to European and East Asian populations, stressing the urgency to expand genetic discovery efforts to more diverse populations worldwide.

Human leukocyte antigen association with familial steroid-sensitive nephrotic syndrome

Steroid-sensitive nephrotic syndrome (SSNS) is the most common form of nephrotic syndrome in childhood. Cases with the familial occurrence of SSNS suggest that genetics may play a role in the disease. Human leucocyte antigen (HLA) alleles have been associated with SSNS. We present genetic findings in nine families (44 participants), each with at least two affected siblings. A total of 19 patients were affected with familial SSNS. Six of nine families showed linkage to markers on chromosome 6p (27.29-33.97 Mbp) (Hg19), especially to markers D6S1629 and D6S1560 on HLA dense region in this location. Interestingly, we also found linkage of disease phenotype of familial SSNS on chromosome 15 (91.7-96.9 Mbp) (Hg19) with a logarithm of odds (LOD) score Z = 3.02.Conclusion: Our findings confirm the linkage of HLA markers on chromosome 6, which strengthens the association of HLA alleles in SSNS. What is Known: • Human leukocyte antigen (HLA) alleles have been associated with idiopathic steroid-sensitive nephrotic syndrome (SSNS). Only few studies have investigated the association between HLA alleles and familial SSNS. What is New: • We present evidence of linkage of familial SSNS to chromosome 6p (27.29-33.97 Mbp) (Hg19), especially to markers D6S1629 and D6S1560 on HLA dense region in this location. We also found linkage of the disease phenotype of familial SSNS on chromosome 15 (91.7-96.9 Mbp) (Hg19) with a logarithm of odds (LOD) score of Z = 3.02 following autosomal recessive inheritance pattern.

Clinical and genetic heterogeneity in familial steroid-sensitive nephrotic syndrome

BACKGROUND

Familial steroid-sensitive nephrotic syndrome (SSNS) is a rare condition. The disease pathophysiology remains elusive. However, bi-allelic mutations in the EMP2 gene were identified, and specific variations in HLA-DQA1 were linked to a high risk of developing the disease.

METHODS

Clinical data were analyzed in 59 SSNS families. EMP2 gene was sequenced in families with a potential autosomal recessive (AR) inheritance. Exome sequencing was performed in a subset of 13 families with potential AR inheritance. Two variations in HLA-DQA1 were genotyped in the whole cohort.

RESULTS

Transmission was compatible with an AR (n = 33) or autosomal dominant (AD, n = 26) inheritance, assuming that familial SSNS is a monogenic trait. Clinical features did not differ between AR and AD groups. All patients, including primary (n = 7) and secondary steroid resistant nephrotic syndrone (SRNS), (n = 13) were sensitive to additional immunosuppressive therapy. Both HLA-DQA1 variations were found to be highly linked to the disease (OR = 4.34 and OR = 4.89; p < 0.001). Exome sequencing did not reveal any pathogenic mutation, neither did EMP2 sequencing.

CONCLUSIONS

Taken together, these results highlight the clinical and genetic heterogeneity in familial SSNS. Clinical findings sustain an immune origin in all patients, whatever the initial steroid-sensitivity. The absence of a variant shared by two families and the HLA-DQA1 variation enrichments suggest a complex mode of inheritance.

Genetics of childhood steroid-sensitive nephrotic syndrome

The pathogenesis of childhood-onset nephrotic syndrome (NS), disparity in incidence of NS among races, and variable responses to therapies in children with NS have defied explanation to date. In the last 20 years over 50 genetic causes of steroid-resistant nephrotic syndrome (SRNS) have been identified, and at least two disease loci for two pathologic variants of SRNS (focal segmental glomerulosclerosis and membranous nephropathy) have been defined. However, the genetic causes and risk loci for steroid-sensitive nephrotic syndrome (SSNS) remain elusive, partly because SSNS is relatively rare and also because cases of SSNS vary widely in phenotypic expression over time. A recent study of a well-defined modest cohort of children with SSNS identified variants in HLA-DQA1 as a risk factor for SSNS. Here we review what is currently known about the genetics of SSNS and also discuss how recent careful phenotypic and genomic studies reinforce the role of adaptive immunity in the molecular mechanisms of SSNS.

HLA-DQA1 and PLCG2 Are Candidate Risk Loci for Childhood-Onset Steroid-Sensitive Nephrotic Syndrome

Steroid-sensitive nephrotic syndrome (SSNS) accounts for >80% of cases of nephrotic syndrome in childhood. However, the etiology and pathogenesis of SSNS remain obscure. Hypothesizing that coding variation may underlie SSNS risk, we conducted an exome array association study of SSNS. We enrolled a discovery set of 363 persons (214 South Asian children with SSNS and 149 controls) and genotyped them using the Illumina HumanExome Beadchip. Four common single nucleotide polymorphisms (SNPs) in HLA-DQA1 and HLA-DQB1 (rs1129740, rs9273349, rs1071630, and rs1140343) were significantly associated with SSNS at or near the Bonferroni-adjusted P value for the number of single variants that were tested (odds ratio, 2.11; 95% confidence interval, 1.56 to 2.86; P=1.68×10(-6) (Fisher exact test). Two of these SNPs-the missense variants C34Y (rs1129740) and F41S (rs1071630) in HLA-DQA1-were replicated in an independent cohort of children of white European ancestry with SSNS (100 cases and ≤589 controls; P=1.42×10(-17)). In the rare variant gene set-based analysis, the best signal was found in PLCG2 (P=7.825×10(-5)). In conclusion, this exome array study identified HLA-DQA1 and PLCG2 missense coding variants as candidate loci for SSNS. The finding of a MHC class II locus underlying SSNS risk suggests a major role for immune response in the pathogenesis of SSNS.

Familial steroid-sensitive idiopathic nephrotic syndrome: seven cases from three families in China

OBJECTIVES

Familial steroid-sensitive idiopathic nephrotic syndrome is rare, and only approximately 3% of patients have affected siblings.

METHODS

Herein, we report seven cases of patients with steroid-sensitive idiopathic nephrotic syndrome from three Chinese families. Mutational screening of the Nphs2 gene was performed in all the patients.

RESULTS

All seven of the familial steroid-sensitive idiopathic nephrotic syndrome cases in our sample exhibited minimal change disease, and one case also presented with mesangial proliferative glomerulonephritis, according to the renal pathology. No significant was associations were found between Nphs2 gene mutations and the onset of proteinuria and nephrotic syndrome in these familial cases.

CONCLUSIONS

The presence of minimal change disease is important, but it is not an unusual finding in patients with familial steroid-sensitive idiopathic nephrotic syndrome, which appears to be clinically benign and genetically distinct from other types of nephrosis.

Is typing for HLA class II alleles beneficial in Indian children with idiopathic nephrotic syndrome?

This study was conducted to test the hypothesis that analysis of HLA class II type alleles will give important information on the prognosis of NS in children. We prospectively studied 100 consecutive children with idiopathic nephrotic syndrome and 202 controls belonging to the same geoethnic background. Typing for HLA Class II alleles at DR and DQ locus was carried out by using SSP (sequence specific oligonucleotides based method). In our study children were more likely to have nephrotic syndrome if the allele DQ-beta1*020X was present as compared to controls. On the other hand, DR-beta1*1001, DR-beta1*130X and DQ-beta1*030X were significantly lower among patients and likely to be protective. On analysing the different steroid response categories, we observed that the allele DQ-beta1*020X was significantly higher in infrequent relapsers (IFR) with a high etiological fraction of 0.714. Children were more likely to be steroid resistant if the allele DR-beta1*150X was present and the etiological fraction was high (0.754). The allele DQ-beta1*030X was significantly lower in steroid resistant patients (p=0.019, RR=0.1819, 95% CI=0.04430-0.7471) and likely to be protective. On analysing the haplotype distribution, we observed that occurrence of DR-beta1*070X-DQ-beta1*020X haplotype was significantly more common among patients with steroid sensitive nephrotic syndrome (23.94%) as compared to controls (12.5%) (p=0.01). In the steroid resistant group we observed that the haplotype DR-beta1*150X-DQ-beta1*060X was significantly more frequent as compared to steroid sensitive patients as well as controls p=0.01. We conclude that HLA typing in Indian children with NS helps to predict relapse frequency and steroid resistance.

Type 1 diabetes mellitus associated with nephrotic syndrome

Nephrotic syndrome (NS) in a patient with diabetes mellitus (DM) first suggests the diagnosis of diabetic nephropathy. However, glomerular diseases other than diabetic nephropathy have been reported in patients with DM. We present a child with type 1 DM (DM1) associated with NS. A 3 year-old boy who was diagnosed with DM1 developed proteinuria in nephrotic range at the 10th month of follow-up. He had remission on steroid treatment without any problem in glycemic control as he was given tapered daily doses instead of an alternate day regimen. He relapsed at the 7th month of follow-up, and cyclophosphamide treatment brought about remission. He had HLA A24, DR4 and DR53 antigens in common with previously reported cases of DM-NS association. The immunological basis of these diseases may have a causal effect on the association, but the etiopathogenesis is still unclear.