Nephrotic Syndrome Study Network

Idiopathic Nephrotic Syndrome (NS) is a rare disease syndrome responsible for approximately 12% of all causes of end-stage kidney disease (ESRD) and up to 20% of ESRD in children. Treatment strategies for Focal and Segmental Glomerulosclerosis (FSGS), Minimal Change Disease (MCD) and Membranous Nephropathy (MN), the major causes of NS, include high dose prolonged steroid therapy, cyclophosphamide, cyclosporine A, tacrolimus, mycophenolate mofetil and other immunosuppressive agents, which all carry significant side effects. Failure to obtain remission using the current treatment approaches frequently results in progression to ESRD with its associated costs, morbidities, and mortality. In the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) registry, half of the pediatric patients with Steroid Resistant Nephrotic Syndrome required renal replacement therapy within two years of being enrolled in the disease registry. FSGS also has a high recurrence rate following kidney transplantation (30-40%) and is the most common recurrent disease leading to allograft loss.

The prevailing classification of Nephrotic Syndrome categorizes patients into FSGS, MCD, and MN, if in the absence of other underlying causes, glomerular histology shows a specific histological pattern. This classification does not adequately predict the heterogeneous natural history of patients with FSGS, MCD, and MN. Major advances in understanding the pathogenesis of FSGS and MCD have come over the last ten years from the identification of several mutated genes responsible for causing Steroid Resistant Nephrotic Syndrome (SRNS) presenting with FSGS or MCD histopathology in humans and model organisms. These functionally distinct genetic disorders can present with indistinguishable FSGS lesions on histology confirming the presence of heterogeneous pathogenic mechanisms under the current histological diagnoses.

The limited understanding of FSGS, MCD, and MN biology in humans has necessitated a descriptive classification system in which heterogeneous disorders are grouped together. This invariably consigns these heterogeneous patients to the same therapeutic approaches, which use blunt immunosuppressive drugs that lack a clear biological basis, are often not beneficial, and are complicated by significant toxicity. The foregoing shortcomings make a strong case that concerted and innovative investigational strategies combining basic science, translational, and clinical methods should be employed to study FSGS, MCD, and MN. It is for these reasons that the Nephrotic Syndrome Study Network is established to conduct clinical and translational research in patients with FSGS/MCD and MN.