Rapidly progressive glomerulonephritis due to coexistent anti-glomerular basement membrane disease and fibrillary glomerulonephritis

Abstract

Anti-glomerular basement membrane (anti-GBM) disease is a major cause of rapidly progressive glomerulonephritis (RPGN). On the other hand, fibrillary glomerulonephritis (GN) typically presents as proteinuria, hematuria and renal insufficiency, but rarely as RPGN. Without electron microscopy, the diagnosis of fibrillary GN can be missed. We report a 68-year-old white woman who presented with RPGN with kidney biopsy demonstrating diffuse crescentic GN on light microscopy. By immunofluorescence, there was bright linear staining of the GBMs and smudgy mesangial staining for immunoglobulin G, C3, and kappa and lambda light chain. Electron microscopy revealed fibrillary deposits in the GBM and mesangium. A serum test for anti-GBM antibody was positive. To our knowledge, this is the first report of coexistence of fibrillary GN in a patient with anti-GBM disease. Electron microscopy is critical to identify the coexistence of other GN in patients presenting with crescentic GN.

Keywords: anti-GBM; anti-glomerular basement membrane disease; crescentic glomerulonephritis; fibrillary glomerulonephritis; rapidly progressive glomerulonephritis.

Fig. 1.

Representative kidney biopsy findings showing FGN with anti-GBM disease. (A) Glomerulus with cellular crescent and mild mesangial matrix expansion. Associated interstitial inflammation is noted (periodic acid–Schiff, 40×). (B) Immunofluorescence staining with IgG demonstrates linear GBM staining as well as segmental smudgy mesangial staining. (C) Electron microscopy shows randomly oriented nonbranching fibrils distributed within mesangium as well as within the peripheral capillary loops.