Epidemiology of pediatric nephrotic syndrome in Brazil: incidence, prevalence, response to steroids and construction of the basis for molecular genetic analyses

Abstract

Nephrotic syndrome (NS) is common in childhood and is an idiopathic disease as a rule. This disorder is usually responsive to treatment with corticosteroids (steroid-sensitive nephrotic syndrome - SSNS), not evolving to impaired renal function. The classification based on response to treatment (SSNS versus SRNS) is an essential indicator of prognosis. However, in 10%-20% of cases there is no response to steroids (steroid-resistant nephrotic syndrome - SRNS), a condition in which up to 50% of the patients develop chronic kidney disease. Monogenic forms account for up to 30% of SRNS cases in pediatric age, including genetic variants in more than 50 genes. The Brazilian network of nephrotic syndrome in childhood (REBRASNI) is a cooperation of three universities to improve the diagnosis and prognosis of NS in childhood. Analysis of the molecular genetics of the disease is one of REBRASNI's objectives, and the epidemiological characterization of SN in Brazil is essential as a first step in planning the investigations required for the REBRASNI aims. This is a crucial prerequisite, since there are regional and ethnic differences in disease frequency and prognosis. In addition, epidemiologic data on this disorder are very scarce in the Southern Hemisphere. The objective of this project is to carry out a detailed epidemiological study on pediatric NS in Brazil, aiming: a) To determine the incidence and prevalence of the disease in children at a national level, b) To know the frequency of SRNS in Brazil, c) To identify the pattern of use and the frequency of response to non-steroidal immunosuppressants in Brazil, d) To establish a Brazilian pediatric NS registry, e) To select centers to build a prospective cohort of pediatric nephrotic syndrome.The research design is an observational, cross-sectional study, with a sampling strategy aimed to represent SN at the national level. Last year, there were 3,105 unique hospitalizations for NS in 623 different public hospitals in Brazil. The median number of cases per hospital was 2 individuals (range = 1 to 66). Hospitals were classified into 2 groups for the sample constitution: G1) Centers that had less than 15 hospitalizations - among the 573 hospitals that had this volume of hospitalizations, 150 centers will be chosen at random (26% of the total); G2) Centers with 15 or more cases: 50 hospitals - hospitals of this group will be visited, totaling 200 hospitals to be contacted in the study. The 150 Group 1 centers will be contacted by phone and / or email and their expected contribution will be the total number of cases being followed up and the number of new cases in the year prior to contact, aiming to meet the objective of determining incidence and prevalence of the disease. The remaining 50 centers with the highest volume will receive a face-to-face visit by researchers from the project, and a random selection of 20 cases will be made in each one. These cases will provide a set of demographic and clinical data that will be collected to meet the other research aims. (AU)