The nephrotic syndrome is a rare disease defined by a proteinuria >3g/24h and a hypoalbuminemia < 30g/L. Genetic and immune are the main causes. The acquired idiopathic nephrotic syndrome presents histologically minimal glomerular lesions, sometimes associated with segmental and focal hyalinosis. The idiopathic nephrotic syndrome (INS) represents 85% of children's glomerular nephropathy and 25-30% of adult's.

Relapses are frequents, and can be pejorative up to 10% and lead to end-stage kidney failure.

Another immune cause is the extramembranous glomerulonephritis mediated by molecular targets specific autoantibodies expressed at the podocytes surface.

Other immune causes include lupus nephropathy, ANCA vascularitis, Goodpasture disease, Berger disease.

Easy diagnosis between these causes can be made with the renal biopsy.

Miss-1, a new protein activated during a inflammatory event, could be an actor in nephrotic syndromes by modifying the podocyte's adhesion on the glomerular basal membrane. This would modulate the structure and function of the slit diaphragm, as well as junctions between the podocyte and the glomerular basal membrane, regulating podocytes' apoptosis.

This project is meant to propose and validate specific and non-invasive diagnostic and prognostic tests for the acquired idiopathic nephrotic syndrome.

These tests rely on the measure of Miss-1 expression in circulating blood cells on flow cytometry and its plasmatic concentration.

To date, no equivalent tests exist to diagnose idiopathic nephrotic syndrome (INS) from other causes.

These simple tests would allow a quick diagnosis of acquired INS by avoiding an invasive renal biopsy. It would also help anticipate the relapses of the disease and guide the treatment modalities as do nowadays the PLA2R antibodies in idiopathic membranous nephropathy.

We will propose the tests to every consent patient, hospitalized in the participating centers (Néphrologie pédiatrique of Robert Debré hospital, Néphrologie adulte of Tenon hospital) with a nephrotic syndrome.

Inclusion Criteria:

• All new hospitalized patient
• Presenting a nephrotic syndrome according to its definition
• For which an anatomopathological diagnostic and its evolution can be or will be carried
• Children of any age can be included if they present a nephrotic syndrome

Exclusion Criteria:

- Patients already treated with glucocorticoids and/or immunosuppressor

All nephrotic patients from the participating centers