A 72-year-old man with diabetes and CKD stage 3a (eGFR 55) is admitted with bilateral leg oedema and frothy urine. 24-hour urine protein is 5.8 g. Renal biopsy shows diffuse glomerulosclerosis on LM; on EM, spike-and-dome pattern with subepithelial electron-dense deposits. The MOST likely diagnosis is:
- A Membranous nephropathy (MN) ✓
- B Diabetic nephropathy (Kimmelstiel-Wilson nodular glomerulosclerosis)
- C Primary FSGS with diffuse foot process effacement
- D Membranoproliferative glomerulonephritis (MPGN)
Explanation
The 'spike-and-dome' pattern on electron microscopy is the pathognomonic finding of membranous nephropathy (MN). The spikes represent GBM extensions between subepithelial immune complex deposits (domes). This pattern, combined with nephrotic-range proteinuria, is diagnostic. Diabetic nephropathy shows Kimmelstiel-Wilson nodular mesangial deposits and diffuse mesangial expansion without spike-and-dome on EM. FSGS shows focal segmental collapse of glomerular tuft with foot process effacement but no immune deposits. MPGN has subendothelial deposits with 'tram-track' GBM splitting. In older males, MN is associated with PLA2R antibodies (primary) or malignancy (paraneoplastic secondary MN).
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.