Fibrillary glomerulonephritis (FGN) is a rare cause of nephrotic syndrome. In three patients (65-year-old male; 57- and 38-year-old females) FGN was diagnosed by percutaneous renal biopsy. Clinically, the disease manifested itself with long term proteinuria and nephrotic syndrome without any associated systemic disorder. Histologically, glomeruli showed deposition of PAS+, fuchsinophilic and Orange G+ materiál in the mesangium and basal membranes. Strong granular immunofluorescence IgG, C3 and weak kappa and lambda light chains mesangial and peripheral deposition were observed in two patients. Electronmicroscopically, deposition of fibrillary material finto mesangium and basal membranes was found. Randomly distributed nonbranching fibrils were 18-28 nm thick. After 10 to 13 months of follow-up, the therapy with corticosteroids and immunosuppressives was without effect, and the disease progressed finto chronic renal failure in two patients; the third patient did well.

        Key words: electron microscopy - fibrillary glomerulonephritis - fibrillary glomerulopathy - immunotactoid glomerulopathy