Fibrillary glomerulonephritis: a diagnosis not to be missed

Fibrillary glomerulonephritis (Fib GN) is among the newly recognized primary glomerular diseases. This rare cause of end-stage kidney disease has characteristic electron microscopic findings based upon the deposition of randomly distributed (18-22 nm) microfibrills in the mesangium and less frequently in the capillary basement membrane. The main differential diagnosis at the pathological level is amyloidosis; however,the apple green birefringence Congo red positivity of amyloid deposition is not seen in Fib GN. Clinically,the patient usually presents with proteinuria of nephrotic range,and the sine qua non for the diagnosis of Fib GN is the availability of high-magnification electron micrographs. Here is a case report of Fib GN with special emphasis on electron microscopy study and its role in the diagnosis.