Fibrillary glomerulonephritis mimicking membranous nephropathy--a diagnostic pitfall

Fibrillary glomerulonephritis complicated by membranous nephropathy in a patient with tuberculosis

Fibrillary glomerulonephritis (FGN) is a morphologically defined entity characterized by glomerular accumulations of non-branching, randomly arranged fibrils; these differ from amyloid fibrils by their larger size and lack of reactivity with Congo red and other amyloid-specific dyes. FGN is a rare disease and may mimic membranous nephropathy under routine light microscopy and immunohistochemistry. However, electron microscopy shows the fibrillary nature of these glomerular deposits. We report a rare case of membranous nephropathy complicated by fibrillary deposits in a 60-year-old man with a history of bone tuberculosis.