WHEN NONCONGOPHILIC GLOMERULAR FIBRILS DO NOT REPRESENT FIBRILLARY GLOMERULONEPHRITIS - NONSPECIFIC MESANGIAL FIBRILS IN SCLEROSING GLOMERULI

In addition to fibrillary glomerulonephritis (FGN), Congo red negative mesangial fibrils may commonly be seen in sclerosing glomerular disea ses. Rarely, these nonspecific mesangial fibrils (NMF) may mimic fibri ls in FGN and cause a differential diagnostic pitfall. Following an in teresting case of sclerosing crescentic glomerulonephritis with abunda nt NMF (which is presented in some detail) we have reviewed our renal biopsy files for a period of two and a half years and found additional 16 cases where the presence of NMF warranted studies to exclude FGN a nd other diseases with fibrillary deposits. The immunofluorescence pat tern characteristically seen in FGN was not present in any of these ca ses. Our data confirm that mesangial fibrillary material seen ultrastr ucturally in sclerosing glomeruli with negative or nonspecific immunof luorescence (IF) represents a nonspecific reaction of the mesangial ma trix to chronic glomerular injury. The presence of NMF should not lead to the erroneous diagnosis of FGN. Negative or nonspecific immunofluo resence, localization to the mesangium in a usually segmental fashion, and the more bundle-like than random arrangement of fibrils are helpf ul diagnostic hints in differentiating NMF from fibrils in FGN.