Randomized Trial Evaluating Mycophenolate Mofetil in Children With Nephrotic Syndrome After Rituximab Treatment

Inclusion Criteria: 1. Children between 1 and 16 years with Frequently-relapsing or Steroid-dependent Nephrotic Syndrome 2. Estimated glomerular filtration rate (eGFR) ≥90 ml/min per 1.73 m2 at study entry. 3. Remission at study entry 4. Patients in whom ≥5 CD20-positive cells/μL are observed in the peripheral blood. 5. Parents willing to give informed written and audiovisual consent. Exclusion Criteria: 1. Patients who have been diagnosed with nephritic- NS, such as immunoglobulin A(IgA) nephropathy, prior to assignment or in whom secondary NS is suspected. 2. Patients showing one of the following abnormal clinical laboratory values: 1\) Leukocytes \< 3000/μL. 2) Neutrophils \< 1500/μL. 3) Platelets \< 50,000/μL. 4) Alanine aminotransferase (ALT) \> 2.5× upper limit of normal value. 5) Aspartate aminotransferase (AST) \> 2.5× upper limit of normal value. 6) Positive for hepatitis B surface (HBs) antigen, HBs antibody, hepatitis B core (HBc) antibody, or hepatitis C virus (HCV) antibody. 7) Positive for HIV antibody. 3\. Patients meeting one of the following infection criteria: 1\) Presence or history of severe infections within 6 months prior to assignment.2) Presence or history of opportunistic infections within 6 months prior to assignment.3) Presence of active tuberculosis.4) Patients with a history of tuberculosis or in whom tuberculosis is suspected.5) Presence or history of active hepatitis B or hepatitis C or hepatitis B virus carrier.6) Presence of human immunodeficiency virus (HIV) infection. 4\. Presence or history of angina pectoris, cardiac failure, myocardial infarction, or serious arrhythmia (findings observed under Grade 4 of the Common Terminology Criteria for Adverse Events (CTCAE)). 5\. Presence or history of autoimmune diseases or vascular purpura. 6\. Presence or history of malignant tumor. 7\. History of organ transplantation. 8\. History of drug allergies to methylprednisolone, acetaminophen, cetirizine, mycophenolate mofetil,rituximab, or any of the above drugs 9\. Uncontrollable hypertension. 10\. Having received a live vaccine within 4 weeks prior to enrollment. 11\. Patients who do not agree with contraception during the study period. 12\. Judged inappropriate for this study by the treating or study physicians.