A 62-year-old woman presented with acute renal failure, hematuria, proteinuria, and increased C-reactive protein level. She was positive for antineutrophil cytoplasmic antibodies (ANCAs) directed against myeloperoxidase (MPO) and negative for anti-glomerular basement membrane antibody. Kidney biopsy confirmed a diagnosis of pauci-immune crescentic glomerulonephritis with no immunoglobulin G staining. Remission was induced with prednisolone and intravenous cyclophosphamide, followed by maintenance therapy with azathioprine, during which MPO-ANCA results became negative. Nine months after the initial presentation, kidney function rapidly deteriorated again in association with hematuria, proteinuria, and increased C-reactive protein level. A second kidney biopsy again showed crescentic glomerulonephritis; however, on this occasion, direct immunofluorescence showed prominent linear staining of the glomerular basement membrane with immunoglobulin G. Test results were strongly positive for glomerular basement membrane antibody, but remained negative for MPO-ANCA. HLA-DR typing showed HLA-DRB1*15011, an allele strongly associated with anti-glomerular basement membrane disease. To our knowledge, this is the only reported case of 2 distinct forms of crescentic glomerulonephritis characterized by separate autoantibody profiles developing sequentially in a patient with proved HLA susceptibility. We speculate that glomerular damage caused by the initial renal insult resulted in a subsequent autoimmune response to autoantigen presented on the HLA-DR susceptibility allele.
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