Pediatric idiopathic nephrotic syndrome (INS) is a rare disease for which the optimal therapeutic strategy has not yet been defined. A network of clinicians treating complicated forms of this disease (grouped within the Société de Néphrologie Pédiatrique, SNP) exists, but to date there is no prospective cohort following up these patients that would facilitate the development of cohort-nested trials. This absence of structured follow up makes it difficult to set up prospective studies.

The main objective is to create a prospective cohort of pediatric INS patients to collect cases treated in SNP centers, to study their epidemiological characteristics, and to provide a basis for comparison for future cohort-nested trials.

In this study, data from patients with INS will be recorded prospectively, regularly and systematically. The cohort will be composed of patients followed by pediatric nephrologists affiliated with the SNP. Metropolitan France, Reunion Island and Mayotte are the geographical areas concerned. It is planned to integrate other French overseas departments and territories, in particular the West Indies.

This is therefore a prospective, multicenter, cohort follow-up study. The data will be centralized via a secure website dedicated to the study.

Data will be obtained from:

• Medical record data (hospitalization/consultations) as part of routine clinical follow-up for patients with active disease. This information will be medically validated and integrated into the database with the help of clinical research staff.
• A telephone interview for annual follow-ups for patients whose absence of active disease no longer requires a systematic medical visit. This structured interview will be administered by telephone by the study's clinical research staff.
• Self-administered or hetero-administered quality of life questionnaires (PEDS-QL), self-administered or hetero-administered treatment compliance questionnaires (Morisky's Score), and questionnaires on the aesthetic impact of treatments (Ferriman's Score). These questionnaires will be centralized and reported to the database by the study's clinical research staff.

Inclusion Criteria:

• Patient under 18 years of age
• With idiopathic nephrotic syndrome (according to SPN criteria) beginning after January 1, 2018
• Child seen at least once in consultation or hospitalization by a pediatrician member of the Society of Pediatric Nephrology
• Residing in France
• Consent signed by parents and patient's agreement to participate (if of age)
• Affiliated to a social security system.

Exclusion Criteria:

• Refusal of the patient or legal representatives to participate in the cohort

Pediatric idiopathic nephrotic syndrome