RecruitingPhase 2Drug trialEfficacy and Safety of Rituximab Versus Mycophenolate Mofetil in Children With Steroid-dependent Nephrotic SyndromeThe goal of this clinical trial is to evaluate the efficacy and safety of rituximab(RTX) and mycophenolate mofetile(MMF) in the treatment of children with low-dose steroid-dependent nephrotic syndrome(SDNS).