Question

A child develops cola-coloured urine, periorbital oedema and hypertension two weeks after a sore throat. Urine microscopy shows red blood cell casts. On electron microscopy of the renal biopsy, which finding is characteristic of this condition?

• A. Subepithelial electron-dense “humps”
• B. Subendothelial deposits with “tram-track” basement membrane splitting
• C. Diffuse effacement of podocyte foot processes with no deposits
• D. Linear ribbon-like deposits along the glomerular basement membrane

Hint:

Post-strep nephritic syndrome - think where the immune deposits sit on EM.

Answer 1

The Correct Option is A

Step 1: Identify the disease. A child with cola-coloured urine, oedema and hypertension 1-2 weeks after a streptococcal infection, with RBC casts (a nephritic picture), has post-streptococcal glomerulonephritis (PSGN).

Step 2: Recall the ultrastructure. PSGN is an immune-complex disease. On electron microscopy the deposits sit on the epithelial (outer) side of the glomerular basement membrane as discrete subepithelial electron-dense “humps”. Light microscopy shows diffuse proliferative GN and immunofluorescence shows a granular “starry-sky” IgG and C3 pattern.

Step 3: Choose the answer. The characteristic EM finding is subepithelial humps.

Step 4: Why the others are wrong - subendothelial deposits with tram-track splitting suggest membranoproliferative GN; diffuse foot-process effacement with no deposits is minimal change disease (nephrotic, not nephritic); linear GBM deposits indicate anti-GBM (Goodpasture) disease.

Key fact: PSGN with RBC casts shows subepithelial humps on EM.