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Kidney Week

Abstract: SA-PO855

AA Amyloid Masquerading as C3 Glomerulonephritis

Session Information

Category: Glomerular Diseases

  • 1401 Glomerular Diseases: From Inflammation to Fibrosis

Authors

  • Paul, Arunava, Eastern Virginia Medical School, Norfolk, Virginia, United States
  • Malhotra, Varun, Eastern Virginia Medical School, Norfolk, Virginia, United States
  • Magoon, Sandeep, Eastern Virginia Medical School, Norfolk, Virginia, United States
  • Rust, Harlan C., Eastern Virginia Medical School, Norfolk, Virginia, United States
Introduction

C3 glomerulopathies are a group of rare kidney disorders characterized by complement dysregulation. We present a case of AA amyloidosis presenting as C3 glomerulonephritis.

Case Description


55-year-old woman with a history of metastatic vulvar squamous cell carcinoma, presented with right lower extremity pain, right groin abscess and acute kidney injury (AKI). Baseline creatinine was 0.46 mg/dL and peaked at 6.9. No nephrotoxins were reported on history or review of medical records. Urinalysis was significant for WBC 21-50/hpf, RBC 0-2/hpf, protein 300 mg/dL, small blood and Urine protein to creatinine ratio was 9g/g. Hep C was positive with HCV RNA PCR-657,000. Complements were normal. Serological and paraproteinemia workup was negative. Kidney biopsy showed MPGN pattern with lesions suggestive of thrombotic microangiopathy ( TMA ) in 80% of capillary loops on light microscopy (LM) and immunofluorescence (IF) was positive for diffuse 3 + mesangial and capillary loop reaction for C3. No reaction to IgG, IgA, IgM, C1q, kappa, lambda or fibrin. Based on LM and IF findings, diagnosis of C3GN and TMA was made, although TMA itself is very uncommon. It was presumed that activation of alternate complement pathway was due to infection. There was minimal endocapillary proliferation which did not fit with typical C3GN with such high serum creatinine level. Electron microscopy (EM) eventually cleared the final diagnosis. EM revealed thin delicate randomly arrayed fibrils within the mesangial matrix and Congo Red and Thioflavin-T staining was positive in the mesangium and capillary loops. What was read as TMA were actually amyloid deposits. Mass spectrography revealed AA Amyloid.

Discussion

This patient presented with multiple challenges in terms of diagnosis. Hepatitis C related MPGN, Infection related glomerulonephritis and paraneoplastic related GN were all considerations. Light microscopy and IF were suggestive of C3GN with TMA which fit clinical picture (and all can present in a similar fashion). Eventually EM clinched the diagnosis. It proved to be a case of mistaken identity. EM is invaluable in making management decisions especially when LM and IF are not corroborating with clinical and pathological findings.
Patient deterioration was rapid and did not pursue active treatment and chose hospice care.