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Review
. 2018 Jul 17:6:200.
doi: 10.3389/fped.2018.00200. eCollection 2018.

Exploring the Clinical and Genetic Spectrum of Steroid Resistant Nephrotic Syndrome: The PodoNet Registry

Affiliations
Review

Exploring the Clinical and Genetic Spectrum of Steroid Resistant Nephrotic Syndrome: The PodoNet Registry

Agnes Trautmann et al. Front Pediatr. .

Abstract

Background: Steroid resistant nephrotic syndrome (SRNS) is a rare condition, accounting for 10-15% of all children with idiopathic nephrotic syndrome. SRNS can be caused by genetic abnormalities or immune system dysfunction. The prognosis of SRNS varies from permanent remission to progression to end-stage kidney disease, and post-transplant recurrence is common. Objectives: The PodoNet registry project aims to explore the demographics and phenotypes of immune-mediated and genetic forms of childhood SRNS, to assess genotype-phenotype correlations, to evaluate clinical management and long-term outcomes, and to search for novel genetic entities and diagnostic and prognostic biomarkers in SRNS. Methods: In 2009, an international registry for SRNS was established to collect retro- and prospective information on renal and extrarenal disease manifestations, histopathological and genetic findings and information on family history, pharmacotherapy responsiveness and long-term outcomes. To date, more than 2,000 patients have been enrolled at 72 pediatric nephrology centers, constituting the largest pediatric SRNS cohort assembled to date. Results: In the course of the project, traditional Sanger sequencing was replaced by NGS-based gene panel screening covering over 30 podocyte-related genes complemented by whole exome sequencing. These approaches allowed to establish genetic diagnoses in 24% of the patients screened, widened the spectrum of genetic disease entities presenting with SRNS phenotype (COL4A3-5, CLCN5), and contributed to the discovery of new disease causing genes (MYOE1, PTPRO). Forty two percent of patients responded to intensified immunosuppression with complete or partial remission of proteinuria, whereas 58% turned out multi-drug resistant. Medication responsiveness was highly predictive of a favorable long-term outcome, whereas the diagnosis of genetic disease was associated with a high risk to develop end-stage renal disease during childhood. Genetic SRNS forms were generally resistant to immunosuppressive treatment, justifying to avoid such pharmacotherapies altogether once a genetic diagnosis is established. Even symptomatic anti-proteinuric treatment with RAS antagonists seems to be challenging and of limited efficacy in genetic forms of SRNS. The risk of post-transplant disease recurrence was around 30% in non-genetic SRNS whereas it is negligible in genetic cases. Conclusion: In summary, the PodoNet Registry has collected detailed clinical and genetic information in a large SRNS cohort and continues to generate fundamental insights regarding demographic and etiological disease aspects, genotype-phenotype associations, the efficacy of therapeutic strategies, and long-term patient and renal outcomes including post-transplant disease recurrence.

Keywords: NPHS2; SRNS; WT1; nephrotic syndrome; steroid resistant nephrotic syndrome.

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Figures

Figure 1
Figure 1
Patient enrolment to the PodoNet Registry. 2,041 children with SRNS have been registered at 72 clinical pediatric nephrology centers in 28 countries since August 2009.
Figure 2
Figure 2
Documented parental consanguinity per country. Only countries with more than 10 registered patients were considered.
Figure 3
Figure 3
Age at first disease manifestation in children with and without an identified genetic cause of steroid-resistant nephrotic syndrome [with copyright permission (1)].
Figure 4
Figure 4
Distribution of underlying histopathologic diagnosis in the first renal biopsy performed in 1,651 children with SRNS from the PodoNet cohort.
Figure 5
Figure 5
Immunosuppressive treatments applied following diagnosis of primary steroid resistance: oral prednisolone (Pred), methylprednisolone pulses (MPR), calcineurin inhibitors (CNI), mycophenolate-mofetil (MMF), cyclophosphamide (CPH). Approximately 50% of children were co-treated with renin-angiotensin-aldosterone-system inhibitors (RAS). Patients responding to the intensified immunosuppressive (IIS) treatment were classified as IIS responsive (green), others as multi-drug resistant (red).
Figure 6
Figure 6
Response to IIS treatment episodes during first year after disease onset in 612 children with SRNS. In total, 232 (38%) patients were treated with more than one treatment protocol during the first year after disease onset. Most efficacious treatment (=best response) was used to classify patients [adapted from Table 2, (2)].
Figure 7
Figure 7
Distribution of SRNS subtypes in the PodoNet cohort according to etiology and treatment responsiveness.
Figure 8
Figure 8
Renal survival by disease category. Patients with partial responsiveness to intensified immunosuppressive (IIS) therapy were classified IIS resistant for this analysis [with copyright permission (2)].
Figure 9
Figure 9
Renal survival by histopathological diagnosis [from Trautmann et al. (2) with copyright permission, supplemental materials].
Figure 10
Figure 10
Proposed diagnostic and therapeutic algorithm for children with CNS/SRNS.

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