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Abstract: PO1461

C3 Glomerulonephritis with Nephritic Factor Treated with Rituximab

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Sawaf, Hanny, Cleveland Clinic, Cleveland, Ohio, United States
  • Nakhoul, Georges, Cleveland Clinic, Cleveland, Ohio, United States
  • Mehdi, Ali, Cleveland Clinic, Cleveland, Ohio, United States
  • Taliercio, Jonathan J., Cleveland Clinic, Cleveland, Ohio, United States
Introduction

C3 Glomerulonephritis (C3GN) is a well described cause of kidney disease that results from dysregulation of the alternative complement pathway. Kidney biopsy demonstrates a membranoproliferative pattern of injury and mesangial C3 staining with minimal or no staining of immunoglobulins on immunofluorescence. C3GN can be due to genetic mutations, autoantibodies against the alternative complement regulators, or monoclonal gammopathy. C3 nephric factor (C3NeF) is an auto-antibody that stabilizes C3 convertase which leads to an increase in activity of the alternate complement pathway. Steroids, mycophenolate mofetil (MMF), rituximab, and eculizumab have been used with varying results. We present a patient with biopsy proven C3GN with C3NeF who was successfully treated with rituximab after failing therapy with MMF.

Case Description

Patient is a 64-year-old male diagnosed with biopsy proven C3GN after being found with decreased kidney function with a peak creatinine of 1.97 mg/dL and nephrotic range proteinuria with a maximal urinary protein excretion of 4.3 g/d. Evaluation revealed low C3 and C4 at 60 mg/dL and 5 mg/dL respectively, negative monoclonal testing, and a C3NeF of 21 unit/mL (reference range 0). Patient was initiated on prednisone 60 mg/day with taper, MMF with a maximal dose 3 grams/day, and valsartan for 2 years with little improvement in clinical parameters. Therapy was switched to rituximab 1 gram on weeks 0, 2, 26. Within 3 months patient had; normalization of complements, negative C3NeF, 0.7 urine protein-to-creatinine ratio (UPCR), and serum creatinine 1.5 mg/dL. Since his initial rituximab regimen 2 years ago, he remains off maintenance therapy, with negative C3NeF, normal complements, 0.1 UPCR, and serum creatinine 1.04 mg/dL.

Discussion

C3GN was successfully treated with rituximab based on the disappearance of C3NeF and improvement in clinical parameters. Rituximab was chosen to target CD20 cells to halt the production of the C3NeF autoantibody. Laboratory response (complements and C3NeF) was seen within 3 months of initial rituximab dosing, and UPCR and serum creatinine required a longer follow up for a nadir. Reoccurrence of relapse is being monitored using serial C3NeF measurements. We believe that targeted B cell therapy should be considered in the treatment of C3GN cases which are C3NeF antibody mediated.