Dear Colleagues,

Nephrotic syndrome (NS) constitutes the most common glomerular disease observed in childhood with an annual incidence of 1-7/100,000 children in US and European cohorts. The initial presentation of the disease is well defined, consisting of massive proteinuria, hypoalbuminemia, clinical oedema, and dyslipidemia. Nephrotic syndrome may be idiopathic or secondary to genetic defects in glomerular split diaphragm or podocyte skeleton. The expansion of human genomic techniques in recent decades has facilitated the recognition of the genetic forms of the disease and led to a constantly increasing panel of various gene mutations, which are at the origin of glomerular protein permeability. Children with congenital NS present the most severe clinical spectrum of the genetic form of the disease, which ultimately progresses to kidney failure. Exploration of treatment regimen aiming at the avoidance of disease-related complications (thromboembolic episodes, recurrent severe infections, etc.) and the reduction in albumin infusion requirements has recently attracted research interest. The idiopathic form of the disease, which represents up to 90% of pediatric cases, includes minimal change disease and focal segmental glomerulosclerosis. The etiology is currently unknown; several immune-mediated along with systemic circulating factors have been implicated in damaged glomerular permeability. Nevertheless, the exact pathogenetic mechanism, the trigger factors of immune dysregulation, and the causes behind the two distinct renal histological findings have not been elucidated yet. Approximately half of patients will present a steroid-sensitive, and the remaining steroid-dependent or steroid-resistant type of the disease. The initial prediction of the disease type is currently problematic. The response rate to the combination of immunosuppressive drugs in steroid-resistant disease types remains relatively low. Therapy with B-cell depleting agents has been successfully employed in pediatric patients, permitting a reduction in frequent relapses and steroid sparing at short-term in steroid-dependent cases, but chronic side effects as well as long-term efficacy are still under question. Moreover, the complications related to the disease or chronic immunosuppressant therapy, the chronicity of the disease, which may persist in adult age, in addition to the need for frequent hospitalizations, ultimately increase patient overall morbidity and deteriorate life quality.

Conclusively, NS remains a challenging disease for the pediatric nephrologist. In this Special Issue, we encourage manuscripts in the form of original research papers, systematic reviews, mini reviews, clinical trials, case reports, and all other types accepted by the journal related to epidemiology, pathogenesis, treatment, outcome, and prognosis in both genetic and idiopathic forms of the disease.

Dr. Nikoleta G. Printza
Dr. John Dotis
Dr. Vasiliki Karava
Guest Editors

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• nephrotic syndrome
• minimal change disease
• focal segmental glomerulosclerosis