A Case of Concurrent Anti-Glomerular Basement Membrane Nephritis and Membranous Nephropathy with Positive ANCA

Introduction: Anti–glomerular basement membrane (GBM) nephritis is rapidly progressive with high rates of progression to end-stage kidney disease. We report a rare case of concurrent anti-GBM nephritis and membranous nephropathy with positive antineutrophilic cytoplasmic autoantibodies (ANCA). Case Description: A 58-year-old male without any past medical history was referred due to a 2-month history of fatigue, loss of appetite, weight loss of 5kg and low-grade fever. He also presented with oliguria over the last few weeks. Urinalysis revealed >100 RBC/HPF and >300 mg/dL protein. Laboratory tests revealed elevated acute phase reactant (ESR 120 mm/h; CRP 9.4 mg/dL), anemia (10.1 g/dL) and significant kidney failure (BUN 76 mg/dL; creatinine 16.0 mg/dL), with positive titers of anti-GBM antibodies (345 U/mL) and myeloperoxidase (MPO)-ANCA (26 IU/mL). Chest computed tomography revealed no pulmonary hemorrhage or interstitial pneumonia. Hemodialysis three times per week was started after admission, and intravenous methylprednisolone pulse therapy with subsequent oral administration of prednisolone (1 mg/kg/day) was initiated. A kidney biopsy was performed, and biopsy findings showed spike formation in the glomerular basement membrane and cellular/fibrocellular crescents (24/29 glom) without signs of vasculitis in arterioles. Immunofluorescence study revealed linear and granular IgG and C3 staining along the capillary walls and showed negative staining for target antigens in membranous nephropathy, including M-type phospholipase A2 receptor (PLA2R). Subepithelial electron-dense deposits were found in electron microscopy. The diagnosis was anti-GBM nephritis with membranous nephropathy. After fourteen sessions of plasma exchange were added, the titers of anti-GBM antibodies declined to 4.8 U/mL, but the patient remained dialysis dependent. Discussion: The patient presented with rapidly progressive glomerulonephritis, and the kidney biopsy revealed crescentic anti-GBM glomerulonephritis in addition to membranous nephropathy. The clinical significance of the presence of membranous nephropathy and MPO-ANCA in anti-GBM nephritis warrants investigation. The poor kidney prognosis in this case implicates possible value from earlier diagnosis and emphasizes the need for identification of more effective treatment strategy.