A case of fibrillary glomerulonephritis with linear immunoglobulin G staining of the glomerular capillary walls.

We report a case of crescentic glomerulonephritis that presented with extensive crescent formation and fibrinoid necrosis in the glomeruli. Immunofluorescence staining was strongly positive for linear and pseudolinear staining of the capillary walls for immunoglobulin G (IgG) in the absence of significant mesangial staining. Histologic examination and immunofluorescence staining suggested a diagnosis of anti-glomerular basement membrane disease. However, electron microscopy showed the presence of numerous fibrillary deposits in the subepithelial areas of the glomerular capillary walls, supporting the diagnosis of fibrillary glomerulonephritis. Test results for circulating anti-glomerular basement membrane antibodies were negative. We report this interesting case to illustrate the point that fibrillary glomerulonephritis should be considered in the differential diagnosis of crescentic glomerulonephritis with linear and pseudolinear IgG deposits within the capillary walls. In such cases, electron microscopy is critical in differentiating the cause of crescentic glomerulonephritis.