Abstract: TH-PO090

Ultrastructural Examination of Glomerular Fibrillary Deposits in Diabetic Nephropathy

Session Information

Category: Glomerular

  • 1004 Clinical/Diagnostic Renal Pathology and Lab Medicine

Authors

  • Nagelkerken, Sophie I., Leiden University Medical Center, Leiden, Netherlands
  • Neeskens, P.h., Leiden University Medical Center, Leiden, Netherlands
  • Bruijn, Jan A., Leiden University Medical Center, Leiden, Netherlands
  • Bajema, Ingeborg M., Leiden University Medical Center, Leiden, Netherlands
Background

In diabetic nephropathy (DN), glomerular fibrillary deposits have been observed but there are no large-scale, ultrastuctural examinations in the literature about the nature of these deposits. We here report our investigation of fibrillary deposits found by transmission electron microscopy (TEM) in DN, and compare results to those in fibrillary glomerulonephritis (FGN).

Methods

Twenty-two patients with autologous biopsy confirmed DN were selected and routine light microscopic evaluation, classification and clinical data were reviewed. TEM was performed and fibril diameter was calculated from 60-90 measurements per glomerulus. For comparison, 7 non-diabetic FGN patients were selected.

Results

For detailed results we refer to Table 1. There were 7 cases with class II, 10 with class III and 5 with class IV DN. Irrespective of class, small, randomly organised fibrils with a diameter of 7-14 nm were present in glomeruli of all cases, while additionally, straight or curved, organised fibrils with a diameter of 17-37 nm were present in 11 cases. No renal comorbidity at time of biopsy or at clinical follow up that could explain fibrillary deposits was present.
FGN patients had similar fibrillary deposits that were either small and randomly organised or had a more organised aspect and a diameter of 13-32 nm. None of the patients had diabetes. IF findings did not contribute to differentiate between DN and FGN, but patients with DN did have a significantly thicker GBM than those with FGN.

Conclusion

Fibrillary deposits found in glomeruli of all 22 DN patients are morphologically similar to those in FGN patients. The widespread presence of fibrils in DN was an unexpected finding; their similarity to fibrils in FGN may complicate the histological diagnosis, especially in patients with clinically overlapping symptoms. Therefore, we are currently investigating their composition using mass spectrometry.

Table 1. Patient characteristics
 DN (n=22)FGN (n=7)
Age (years)55 ± 1455 ± 10
Gender = male17 (77%)3 (43%)
DM typeType 15 (23%)Not applicable
Type 216 (73%)
MODY1 (5%)
DM duration (years)15 ± 14Not applicable
Clearance (ml/min/1.73m<2>)43 ± 2841 ± 27
Proteinuria (g/day)6 ± 37 ± 6
Follow-up (years)3 [0 -19]0 [0-7]

Values are depicted as mean ± SD, median [min-max] or as number of patients(%).

Funding

  • Private Foundation Support