NPHS3: new clues for understanding idiopathic nephrotic syndrome

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.

Parental attitudes to genetic testing differ by ethnicity and immigration in childhood nephrotic syndrome: a cross-sectional study

Background

Studies in the USA report differences in opinion among parents of different ethnic groups toward genetic testing for their child; however, there are no studies that address this issue in the diverse ethnic and immigrant population in Canada.

Objective

This study aims to determine whether ethnicity and immigration status influences parental interest in clinical genetic testing for a potentially progressive kidney disease.

Design

This is a cross-sectional study.

Setting

Participants were recruited from the Greater Toronto Area, Canada.

Participants

The study included 320 parents of children ages 1–18 years with nephrotic syndrome enrolled in the Insight into Nephrotic Syndrome: Investigating Genes, Health and Therapeutics (INSIGHT) observational cohort study.

Measurements

Demographic, ethnicity, immigration, and child specific factors as well as interest in genetic testing were collected through self-reported questionnaires administered at baseline study visit.

Methods

Logistic regression models were used to examine association of ethnicity and immigration status with interest in genetic testing.

Results

The majority of parents (85 %) were interested in genetic testing for their child. South Asian and East/Southeast Asian parents had 74 and 76 % lower odds of agreeing to genetic testing when compared to Europeans (odds ratio (OR) 0.26, 95 % confidence interval (CI) 0.10–0.68; OR 0.24, 95 % CI 0.07–0.79, respectively) after controlling for age and sex of child, age and education level of parent, initial steroid resistance, and duration of time in Canada. Immigrants to Canada also had significantly lower odds (OR 0.29, 95 % CI 0.12–0.72) of agreeing to genetic testing after similar adjustment. Higher education level was not associated with greater interest in genetic testing (OR 1.24, 95 % CI 0.64–2.42).

Limitations

Participants have already agreed to aggregate genetic testing for research purposes as part of enrolment in INSIGHT study.

Conclusion

While majority of parents were interested in genetic testing for their child, immigrants, particularly South Asians and East/Southeast Asians, were more likely to decline genetic testing. Genetic counseling needs to be tailored to address specific concerns in these parental groups to maximize informed decision-making in the clinical setting.

Trial registration

ClinicalTrials.gov, NCT01605266

Late steroid resistance in childhood nephrotic syndrome: do we now know more than 40 years ago?

The formation of steroid resistance in children with nephrotic syndrome (NS) who were initially steroid responsive was described decades ago but has not been studied in sufficient depth. Except for the International Study of Kidney Disease in Children, conducted more than three decades ago, when only cyclophosphamide was available as a second-line agent in steroid-resistant NS, only a handful of small studies have addressed the problem of late steroid resistance (LSR) over the past 40 years. Epidemiology and risk factors for the formation of LSR and differences in outcomes when compared with initial steroid resistance still remain unknown. While multiple second-line treatment choices (calcineurin inhibitors, mycophenolate mofetil, rituximab) exist today, therapeutic approaches to the patients with LSR remain empirical, as no evidence-based data have become available. In the current issue of Pediatric Nephrology, Straatmann et al. report retrospective data on the treatment outcomes for 29 pediatric NS patients with LSR from eight participating centers of the Midwest Pediatric Research Consortium. The authors describe a current pattern of second-line agents used in their cohort and show that the majority of patients (66 %) achieved complete or partial remission after a period of observation for 85 ± 47 months. The authors also describe the data on renal histology. While these data represent an important step forward in our understanding of LSR, further work is needed before firm clinical recommendations can be made. Large-scale prospective studies are required to answer important questions about the epidemiology, genetics and outcomes in late steroid-resistant NS, explore the role of medication adherence and develop evidence-based practice guidelines.

Familial forms of nephrotic syndrome

The recent discovery of genes involved in familial forms of nephrotic syndrome represents a break-through in nephrology. To date, 15 genes have been characterized and several new loci have been identified, with a potential for discovery of new genes. Overall, these genes account for a large fraction of familial forms of nephrotic syndrome, but they can also be recognized in 10-20% of sporadic cases. These advances increase diagnostic and therapeutic potentials, but also add higher complexity to the scenario, requiring clear definitions of clinical, histopathological and molecular signatures. In general, genetic forms of nephrotic syndrome are resistant to common therapeutic approaches (that include steroids and calcineurin inhibitors) but, in a few cases, drug response or spontaneous remission suggest a complex pathogenesis. Finally, syndromic variants can be recognized on the basis of the associated extra-renal manifestations. In this educational review, clinical, histological and molecular aspects of various forms of familial nephrotic syndrome have been reviewed in an attempt to define a rational diagnostic approach. The proposed model focuses on practical and economic issues, taking into consideration the impossibility of using genetic testing as starting diagnostic tool. The final objective of this review is to outline a diagnostic flow-chart for clinicians and geneticists and to generate a rational scheme for molecular testing.

Genetic forms of nephrotic syndrome: a single-center experience in Brussels

The aim of the study was to present our experience in treating children with genetic forms of nephrotic syndrome and diagnosing these diseases. We retrospectively reviewed the clinical data, mutational analyses, histopathological features, treatment modalities, and outcome of 26 consecutive children (20 families) suffering from congenital and/or steroid-resistant nephrotic syndrome who were assessed by genetic analysis. Ten out of 26 children (38%) had congenital nephrotic syndrome, 4/26 (15%) had infantile nephrotic syndrome, 10/26 (38%) had late-onset nephrotic syndrome, and 2/26 (9%) had asymptomatic proteinuria. We detected a mutation in 21/26 (81%) patients and in 15/20 (75%) families. NPHS1 mutation analyses were positive in 4/20 (20%), NPHS2 mutations in 4/20 (20%), WT1 mutations in 4/20 (20%), and PLCE1 mutations in 3/20 (15%) families. NPHS1 and PLCE1 mutations were solely found in patients with the earliest onset. The majority of patients, especially those with early onset of nephrotic syndrome, had serious adverse events related to the nephrotic status, and 19/26 (73%) reached end-stage renal failure at a median age of 27 months. Genetic forms of nephrotic syndrome comprise a heterogeneous group of genetic mutations. The progression toward end-stage renal failure is the rule but is highly variable between patients.