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Abstract: SA-PO675

C3 Glomerulonephritis (C3GN) in a Patient With Marginal Zone Lymphoma Responsive to Rituximab Therapy

Session Information

Category: Glomerular Diseases

  • 1302 Glomerular Diseases: Immunology and Inflammation


  • Massoud, Mark N., University of Utah Health, Salt Lake City, Utah, United States
  • Sammons, Stephen R., University of Utah Health, Salt Lake City, Utah, United States
  • Revelo Penafiel, Monica Patricia, University of Utah Health, Salt Lake City, Utah, United States
  • Abraham, Josephine, University of Utah Health, Salt Lake City, Utah, United States

We present the case of a patient with Marginal Zone Lymphoma diagnosed later with C3GN and treated consequently with Rituximab with complete renal response

Case Description

An 81-year-old man was diagnosed with IgM-kappa Monoclonal Gammopathy of Undetermined Significance (MGUS) in 2016 during evaluation for peripheral neuropathy and was found to have a CD5/CD10-negative Marginal Zone Lymphoma. In 2019, microscopic hematuria and proteinuria (UPCR 904 mg/g) were identified which prompted a Nephrology referral. At this time, he was noted to have low serum C3 and C4 levels, kappa-lambda ratio of 2.2 and stable renal function (serum creatinine 1.1-1.2 mg/dL). A renal biopsy was obtained in May 2019 which was significant for focal proliferative glomerulonephritis with dominant C3 deposits and strong IgM staining of capillary loops and mesangial matrix. His proteinuria improved with ACE-I (UPCR < 115 mg/g), and he remained under surveillance for his MGUS/MZL and off any therapy directed at his C3GN until January 2021 when he developed deterioration of renal function (serum creatinine up to 1.7 mg/dL), worsening proteinuria (UPCR 960 mg/g), hypocomplementemia and elevated kappa-lambda ratio of 4.3 with pancytopenia. In March 2021, he underwent 4 weeks of rituximab therapy, after which his proteinuria, complement levels, and renal function improved. These improvements have persisted thus far for a year after his rituximab therapy.


C3GN is a rare type of GN in which dysregulation of the alternative complement pathway results in deposition of C3 within the glomeruli. C3GN can be associated with monoclonal gammopathy and can lead to renal impairment. Patients usually present with hematuria, proteinuria, variable degree of renal dysfunction and hypocomplementemia. If left untreated, patients could progress to ESRD. Diagnosis is established with a renal biopsy showing glomerular C3 and monoclonal Ig deposits on IF in the kidney. Treatment of C3GN in patients with monoclonal gammopathy should be directed at the underling clone, and targeted therapy can lead to improved renal survival.