Razionale

Fibrillary glomerulonephritis (FGN) is a rare primary glomerular disease (0.5-1% of renal biopsies). It's defined by the haphazardly arranged, straight fibrils measuring 10-to-30nm in thickness at electronic microscopy (EM). Light microscopic (LM) features are heterogeneous; most cases exhibit mesangial expansion with or without basal membrane duplication. Glomerular deposits are Congo-red–negative, which distinguishes it from amyloidosis. We report about all FGN cases followed at our hospital.

Casistica e Metodi

All consecutive patients with a biopsy-proven FGN performed at S.Orsola-Malpighi-Hospital of Bologna between 2008 and 2012 were included.

Risultati

In 145/450 biopsies, EM was performed. In four patients FGN was diagnosed (Table 1). Mean age was 56±11 years. An underlying disease was found in three patients: mixed-connective-tissue-disease, Coxackie-related endocarditis, MGUS. Clinical presentation included nephrotic proteinuria (100%), acute renal failure (25%), haematuria (75%), and hypertension (50%). The LM pattern was different. On immunofluorescence, polyclonal IgG and complement were evident. Two patients received steroids alone, two in association with mycophenolate-mofetil (N.1) or cyclophosphamide/azatioprine (N.4). At 6-month follow-up, patient 1 was dialysis-dependent; patient 2 and 3 preserved normal renal function with significant proteinuria reduction to 1 and 2 g/day at 6-month and one-year follow-up, respectively. Patient 4 recovered renal function and proteinuria disappeared at 4-year follow-up.

Table1. Patients Characteristics

Conclusioni

FGN is a rare glomerular entity; however it can be under-diagnosed because of the lack of a specific LM/IF pattern. Thus EM is essential for its diagnosis. Unlike the prior series, FGN seems to be rarely idiopathic, and underlying diseases are not uncommon.