On electron microscopy of a renal biopsy from a 6-year-old child with nephrotic syndrome, diffuse effacement of podocyte foot processes is seen with no immune deposits and normal light microscopy. Immunofluorescence is negative. The pathogenesis involves:
- A Loss of glomerular polyanion barrier and podocyte injury mediated by a circulating permeability factor ✓
- B Subepithelial immune complex deposition activating complement
- C Anti-GBM antibody directed against type IV collagen alpha-3 chain
- D Mesangial IgA deposits causing cytokine-mediated podocyte injury
Explanation
This is minimal change disease (MCD), the most common cause of nephrotic syndrome in children. The morphologic hallmark is diffuse foot process effacement on EM with absent immune deposits on IF. The glomerular polyanion barrier (heparan sulfate proteoglycans on GBM) is lost, allowing albumin to filter. A circulating CD80-inducing lymphokine (possibly an abnormal T-cell-derived permeability factor) is implicated; splenectomy and cyclophosphamide responses support T-cell dysregulation. Anti-GBM disease (Goodpasture) shows linear IgG; IgA nephropathy shows mesangial IgA.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.