Part A: Clinical information
Gender, Age
Male, 52 years old
Previous illnesses
None
Time period since the onset of the first symptoms
Very short: proteinuria detected during a medical check-up after which patient was referred to a nephrologist
Presentation
Rapid decline of eGFR in 2 months accompanied by proteinuria. No hematuria. No history of kidney disease in the family. Otherwise healthy man.
Laboratory parameters
Proteinuria: 1.3 grams.
M protein: negative
eGFR: 24
ANCA negative.
Why was the decision made for a biopsy?
Relatively rapidly progressive renal function deterioration of unknown cause.
How long after the first symptoms was the biopsy conducted?
Approximately 2 months.
Suspected diagnosis of the indication for biopsy?
The clinical question was: explanation for renal insufficiency? TIN? Other?
Note related to annotations: To avoid obscuring the lesions, the annotations are deliberately positioned close to, but not directly over, the lesion areas.
Part B: Kidney biopsy findings
Description of light microscopy:
Kidney biopsy with approximately 16 glomeruli. Only cortical tissue. No global glomerulosclerosis. Glomeruli have preserved architecture, but variable amounts of inflammatory cells are present in capillary loops. The inflammatory cells seem to be a combination of mononuclear cells, some monocytes and rarely, granulocytes. It may be difficult to name all the inflammatory cells separately because we see them from different angles: some clear examples have been annotated. In relation to the inflammation, there is slight endothelial swelling. No clear-cut fibrinoid necrosis or crescent formation. No apparent lesions of GBM (glomerular basement membrane). No chronic lesions like FSGS (focal segmental glomerulosclerosis). Tubulointerstitium is very nicely preserved. No inflammatory infiltrates, no IFTA (interstitial fibrosis and tubular atrophy). Slight intimal fibrosis of arteries.
Immunofluorescence:
IF: 3+ positivity mainly in mesangial areas of C3. Other staining (IgA, IgG, IgM, C1q and light chains) are negative.
Electron Microscopy (EM):
EM shows numerous translucent deposits in the mesangial areas.
Considerations:
This is a typical example of a patient in whom the diagnosis C3G was not considered right away. The IF in combination with EM are characteristic of C3G. However, it should be noticed that C3G has a variable pattern by light microscopy. The presence of endocapillary hypercellularity with some granulocytes may hint at the possibility of a post-infectious disease, but the patient has no history of an infection preceding his clinical symptoms. Also, there are no humps by EM that would be pointing towards a post-infectious disease.