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Abstract: PO1744

Complement 3 Glomerulonephritis in a Patient with Microscopic Polyangiitis

Session Information

Category: Trainee Case Report

  • 1202 Glomerular Diseases: Immunology and Inflammation


  • Siddiqui, Hammad, Robert Wood Johnson University Hospital, New Brunswick, New Jersey, United States
  • Ahmed, Ayesha, Robert Wood Johnson University Hospital, New Brunswick, New Jersey, United States
  • Saleem, Bushra Z., Robert Wood Johnson University Hospital, New Brunswick, New Jersey, United States

C3GN is a rare disorder of excess alternative complement pathway activation, with renal biopsy characteristic of glomerular C3 deposits. We present a unique case, where patient has H/O MPA, admitted for AKI and hematuria, found to have C3GN on renal biopsy.

Case Description

69 yo M with H/O CKD stage 4 due to microscopic polyangitis (baseline Cr 2.6 - 2.9), spinal stenosis, HTN and BPH presented with complaint of painless hematuria, epistaxis, decrease UOP and weight gain x 4 days. He was diagnosed with MPA in 2005 after a renal biopsy, recieved treatment with steroids, Cyclophosphamide for 18 months, switched to MMF for 2 years and then to Azathioprine which was discontinued due to intolerance (off all immunosuppressant’s since 2012.). On admission labs; BUN/Cr 90/6.5, K 5.6, ESR 39, C-RP 1.24, P-ANCA and MPO positive. UA +3 protein, +3 blood, > 182 RBCs and 16 WBCs. Random urine protein > 600 mg per dl. C3 was low (44.1), C4 normal. AH50 was low (36.1%). Hepatitis panel, C-ANCA, PR-3 and anti-GBM were negative. Pt was admitted with preliminary diagnosis of AKI on CKD 2/2 MPA flare and was started on pulse dose of steroid. He was also started on HD and plasmapheresis. Renal biopsy showed active crescents with strong C3 global glomerular staining in the mesangium and the capillary wall and trace to no staining of IgG, IgA, IgM, C1q, kappa, lambda. S. EM showed measnagial and sub endothelial deposit suggestive of active crescentic C3 GN.


C3 GN is rare in clinical practice. Incidence is estimated to be 2–3 cases per 1,000,000 in the United States. MPA, like other ANCA-associated vasculitis, is typically associated with a pauci-immune GN. We presented a case with signs, symptoms, labs and histopathology consistent with both C3GN and MPA. It is unclear whether this patient truly had both diseases, which are typically caused by different immunologic pathways. Depressed C3 levels and normal C4 levels, diffuse glomerular C3 deposits on immunohistochemistry, and subendothelial deposits on electron microscopy strongly supports the diagnosis of C3GN in our patient with MPA.