Fibrilo-Tactoid Glomerulonephritis: A Possible Novel Morphological Variant

Fibrillary and immunotactoid glomerulonephritis are infrequent causes of primary nephrotic range proteinuria and are poorly understood. Recent significant developments include the discovery of DNA JB9 antigen in fibrillary glomerulonephritis. Here, we present a case of a middle-aged woman who presented with nephrotic range proteinuria, hematuria, and normal renal function. Renal biopsy revealed fibrils that were randomly arranged on electron microscopy. They were of small size and congo red negative similar to the ones found in fibrillary glomerulonephritis, but were also DNA JB 9 negative, and had a hollow core like in immunotactoid glomerulopathy. Though we try to classify these conditions into either immunotactoid glomerulonephropathy (ITGN) or fibrillary glomerulonephritis (FGN), there are scenarios such as this case where it does not fit into either and is probably an overlap or intermediate variant of these two conditions. Pathological features of these glomerulonephrites are discussed together with their clinical implications, treatment choices, and diagnostic importance.