ANCA-ASSOCIATED VASCULITIS WITH ISOLATED C3 IMMUNOFLUORESCENCE AND ELECTRON-DENSE DEPOSITS: A CASE REPORT
Dr Craig Coorey1,2,3, WILLIAM JAMES1, SANJEEV BAWEJA1, VENKAT MANICKAVASAGAM1, VICTORIA SASONGKO1
1Department of Renal Medicine, Lismore Base Hospital, Lismore, Australia, 2School of Medicine, University of Western Sydney, Campbelltown, Australia, 3Faculty of Medicine and Health, The University of Sydney, Camperdown, Australia
Background: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is typically characterised by a lack of immune complex deposition on immunofluorescence and electron microscopy. The presence of isolated C3 immunofluorescence and electron-dense deposits is unusual and may present a dilemma regarding the diagnosis of ANCA-associated vasculitis versus C3 glomerulopathy.
Case Report: A 52-year-old female was referred by a urologist with acute kidney injury (serum creatinine of 174 umol/L, baseline 65 umol/L two months prior) and macroscopic haematuria. She had a background history of elevated body mass index (42.9 kg/m2) and psoriatic arthritis treated with Leflunomide and Methotrexate. On examination, she was hypertensive (blood pressure 160/88 mmHg) with urine showing dysmorphic red cells and spot urine albumin:creatinine ratio of 137.0 mg/mmol. She had atypical ANCA with elevated myeloperoxidase antibodies level > 222 international units/mL (ref < 6) and no detectable proteinase 3 antibodies. The remainder of the glomerulonephritis screen including serum complements, paraprotein and free light chains was negative. Renal biopsy demonstrated changes with acute tubular necrosis, three glomeruli containing areas of fibrin formation likely representing areas of tuft necrosis and no cellular crescents. Immunofluorescence demonstrated C3 mesangial staining (1-2+) with isolated capillary wall staining. The electron microscopy showed scattered intramembranous, subepithelial and paramesangial deposits and marked effacement of foot processes. She was treated empirically for ANCA-associated vasculitis with a pulse of intravenous methylprednisolone followed by oral Prednisolone (per PEXIVAS study) and Rituximab with improvement in her renal function.
Conclusions: ANCA-associated vasculitis with immune complex deposition, mimicking a C3 glomerulopathy on renal biopsy, is increasingly recognised. Close follow up is required and response to treatment monitored in cases where there is diagnostic uncertainty regarding the primary lesion.
Biography:
Craig Coorey is a currently a second year renal advanced trainee in the Central South West Regional Renal Network.