Fig. 1

Renal biopsy findings. a Periodic acid-Schiff staining (40×), b periodic acid-methenamine silver staining (40×), c immunostaining for fibrinogen, and d electron microscopy findings (2,000×). Fifteen glomeruli (3 were completely hyalinized, and 12 were mostly hyalinized) exhibit evident crescent formation, with transitioning to fibrous crescents. The glomerular loops are collapsed and destroyed with fibrin deposition. Expansion of the mesangial matrix and an increase in the mesangial cell count are observed, although no double contours or spike formation of the glomerular basement membranes are observed. Lymphocyte infiltration is evident in the tubular interstitium, and 60–70 % of all renal tubules are atrophied. Moderate arteriosclerosis resulting from intimal thickening and medial atrophy is observed in the interlobular arteries (a, b). Immunofluorescence failed to detect the expression of IgG, IgA, IgM, C3, C4, or C1q, and only fibrinogen expression is observed in the crescents (c). Electron microscopy reveals no electron-dense deposits, and podocyte degeneration is observed with evident disappearance of the podocyte foot processes (d)