A 25-year-old woman with SLE has nephrotic-range proteinuria. Renal biopsy shows 'wire loop' capillary deposits on light microscopy. Immunofluorescence shows 'full house' positivity (IgG, IgA, IgM, C3, C1q). Electron microscopy shows subendothelial deposits. This represents:

• A ISN/RPS Class IV lupus nephritis (diffuse) ✓
• B ISN/RPS Class II lupus nephritis
• C ISN/RPS Class V lupus nephritis (membranous)
• D Membranoproliferative glomerulonephritis type I

Explanation

Wire-loop capillary lesions on light microscopy represent massive subendothelial immune complex deposits that thicken the capillary walls, creating a rigid hyaline appearance. 'Full house' immunofluorescence (all immunoglobulin classes plus complement) with subendothelial deposits is pathognomonic of Class IV (diffuse proliferative) lupus nephritis, the most severe class involving ≥50% of glomeruli. This has the worst prognosis among lupus nephritis classes. Class V shows subepithelial deposits (similar to membranous nephropathy); Class II shows only mesangial deposits.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.