From Immune System Damage to Podocyte Cell Damage: Prospective Database and Biological Collection of Patients (Children and Adults) With MGLS and HSFP

Inclusion Criteria: * First episode of idiopathic nephrotic syndrome in a child aged 12 months to 18 years with a weight \> 10 kg and biologically defined as proteinuria \> 0.20 g / mmol creatinuria and hypoalbuminemia \<25 g / mmol * First episode of NIS defined in adults as albumin level \<30 g / L and a urinary protein/creatinine ratio (UPCR) ≥ 300 mg / mmol systematically associated with the performance of a renal anatomopathological examination and characterized by the absence of identifiable lesions by light microscopy (SNLGM) or the presence of HSF lesions. * For adults: signed informed consent to participate in the study * For children: patients will be informed and a written informed consent form will be signed by both parents of the children at inclusion * Patients affiliated to the French health system Exclusion Criteria: * Patients who have previously received corticosteroids and/or immunosuppressants * Patients with reduced CH50 and/or low C3 and/or low C4 and/or low C4 (in some cases increased sC5b9 and/or presence of a C3 nephritic Factor; an anti-C3b...) * SNLGM resulting from a secondary process (lymphoid hematopathies or neoplasia) or occurring following the administration of a treatment known to be associated with an SNLGM (lithium, interferon, non-steroidal anti-inflammatory drugs) * Non-primary FHH (absence of Nephrotic Syndrome, etiological assessment revealing FHH secondary to an identified cause (genetic or not), no introduction of corticosteroids or immunosuppressants as first-line treatment) * Positive serological screening test for HIV, hepatitis B or C * Positive immunological tests for antinuclear and anti-DNA antibodies or anti-PLA2R1 and anti-THSD7A * Patient under guardianship or curatorship