Fibrillary glomerulonephritis: a rare entity with unique ultrastructural characteristics

Fibrillary glomerulonephritis (FGn) is characterized by deposition of randomly arranged polyclonal immune deposits in glomerular matrix¹,². A 56-year-old hypertensive patient presented to our hospital with proteinuria (3.04 g/24 hours) and an elevated serum level of creatinine (391 µmol/L). Electron microscopic evaluation of kidney biopsy specimens set the diagnosis of fibrillary glomerulonephritis (Figure 1). There was no evidence of monoclonal components in the blood and urine. Antinuclear and anti-double-stranded DNA antibodies, complement components C₃ and C_4, and markers of viral hepatitis were also negative. The benefit of immunosuppressants is limited,³ and half of patients progress to kidney failure within 2 years¹-³.

Figure 1
Electron microscopy evaluation demonstrates deposition of organized fibrils with consecutive expansion of mesangial matrix and permeation of lamina densa of the glomerular basal membrane (GBM) (Image A: hollow arrow). Visceral epithelial cells (podocytes) show complete effacement of foot process (Image A: black arrows). At higher magnification (x 60.000), the fibrils are randomly arranged and non-branching, measuring 15 to 18 nm in diameter (Image B).

References

• ¹
  Rosenstock JL, Markowitz GS, Valeri AM, Sacchi G, Appel GB, D'Agati VD. Fibrillary and immunotactoid glomerulonephritis: distinct entities with different clinical and pathologic features. Kidney Int. 2003 Apr;63(4):1450-61.
• ²
  Azevedo A, Cotovio P, Góis M, Nolasco F. Rare diagnosis in a patient with diabetes with nephrotic proteinuria. BMJ Case Rep. 2019 Jan;12(1):bcr-2017-223835.
• ³
  Pronovost PH, Brady HR, Gunning ME, Espinoza O, Rennke HG. Clinical features, predictors of disease progression and results of renal transplantation in fibrillary/immunotactoid glomerulopathy. Nephrol Dial Transplant. 1996 May;11(5):837-42.

Publication Dates

• Publication in this collection
  25 July 2022
• Date of issue
  Jan-Mar 2023

History

• Received
  11 Jan 2022
• Accepted
  16 May 2022