Pediatric Nephrotic Syndrome in Brazil: Results from a National Cohort of 772 Cases

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Background: Characterizing pediatric nephrotic syndrome (NS) is crucial to predict long-term outcomes. However, data on this disease condition are yet scarce in developing countries. Methods: We conducted a retrospective epidemiological study using a nationwide representative sample comprising 16 centers and 772 cases. Cox regression was used to model stage 5 chronic kidney disease (CKD)-free survival, with response to steroid therapy as the explanatory variable, and sex, ethnicity, and family history of nephrotic syndrome as covariates. Results: There was a slight male predominance in the cohort (436 cases, 56% of the total). The median age at disease onset was 3.3 years (IQR: 2.2 to 5.7), and the follow-up period for the sample was 5.4 years (IQR: 2.8 to 9.1). A family history of NS was reported in 55 cases (9.7% of valid responses to this question). The final classification of the response to steroid treatment revealed 317 (42%) cases of steroid-sensitive NS, 238 (31%) patients with steroid-dependence/frequent relapses, 167 (22%) cases of steroid-resistant NS, and 39 (5%) patients with secondary steroid resistance (initial positive response to steroids followed by subsequent resistance). Considering the whole sample, 317 (41%) underwent a kidney biopsy and only 15 (2%) children had a genetic test, yielding a low molecular genetic diagnostic rate. At the end of the follow-up, 57 children (7.7%) had progressed to stage 5 chronic kidney disease (CKD). CKD stage 5-free survival over a ten-year follow-up period was estimated to be 90% (95% CI: 87% to 94%) and the median time to the event was 5 years. According to the response to steroids, resistance (HR: 63, p < 0.001) and secondary resistance (HR: 11, p = 0.031) were associated with a worse prognosis. A multivariable model adjusted for sex, ethnicity, and family history of NS did not alter the magnitude or direction of the associations with steroid responses. Conclusions: Steroid resistance was observed at a higher frequency than typically reported in the literature, and there is low access to molecular diagnosis in the whole country. Moreover, our data reaffirm the negative impact of resistance and secondary resistance to steroids on the prognosis of pediatric nephrotic syndrome. Funding: Government Support - Non-U.S.

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