Open-label, randomized, controlled trial due to value whether the monoclonal antibody rituximab is non-inferior to steroids in maintaining remission in juvenile forms of SDNS.

The investigators will enroll 30 pediatric patients affected by idiopathic nephrotic syndrome, who have been in treatment with steroids for at least one year. The lowest dose of drug required to maintain a stable remission will be between 0.4 and 0.7 mg/ kg/ day.

This trial provides an initial run-in phase of one month during wich remission will be achieved by means of a standard oral prednisone course. Once remission has been achieved children will be randomized in a parallel arm open label RCT to continue prednisone alone for one month (control) or to add a single intravenous infusion of rituximab (375 mg/m2 - intervention). Prednisone will be tapered in both arms after one month.

Inclusion Criteria:

• Age between 1 and 16 years.
• Steroid-dependent idiopatic nephrotic syndrome for a minimum of 6 to a maximum of 12 months at the time of study entry, regardless of disease duration.
• Low-dose steroid dependence (between 0.4 and 0.7 mg/ kg/ day)

Exclusion Criteria:

• Positivity of autoimmunity tests (ANA, nDNA, ANCA) or reduced C3 levels
• Histological pattern suggestive for congenital anomalies (diffuse mesangial sclerosis without IgM deposits, cystic-like tubular dilations, evidence of mithocondrial damage on electronic microscopy.
• Histological pattern not correlated with idiopathic nephrotic syndrome in the pediatric age (membranous glomerulonephritis, lupus nephritis, diffuse and/or localized vasculitis, amyloidosis).
• Evidence of homozygous or heterozygous mutations in podocitary genes commonly involved in the pathology (NPHS1, NPHS2, WT1).
• Estimated glomerula filtration rate (eGFR) < 60ml/min.
• Presence of circulating IgM against HCV, HBV, parvovirus or mycoplasm.