Clinical Study of Rituximab for the Treatment for Idiopathic Membranous Nephropathy With Nephrotic Syndrome

To confirm the efficacy and safety of rituximab (genetical recombination) intravenously administered to idiopathic membranous nephropathy with nephrotic syndrome.

Inclusion Criteria: 1. Patients who undergo kidney biopsy and are diagnosed as having idiopathic membranous nephropathy prior to the obtainment of informed consent 2. Patients who are diagnosed as having nephrotic syndrome prior to the obtainment of informed consent and receive no steroids or immunosuppressants within 12 weeks prior to the obtainment of informed consent 3. Patients with urine protein-creatinine ratio ≥ 3.5 g/gCr at the screening 4. Patients with hypoalbuminemia (serum albumin ≤ 3.0 g/dL) at the screening 5. Patients aged 15 years or older at informed consent 6. Patients who give voluntary written consent after having received adequate information on this study (legally acceptable representatives should also give consent for underage patients, and informed assent should be obtained from children) Exclusion Criteria: 1. Patients with primary nephrotic syndrome other than membranous nephropathy (IgA nephropathy, minimal change disease, focal segmental glomerulosclerosis and so forth), and patients with secondary nephrotic syndrome (autoimmune disease, metabolic disease, infection, allergic/hypersensitive disease, tumor, and drug-induced disease) 2. Patients with the renal function lowered (eGFR \