A 28-year-old woman presents with arthralgia, malar rash, oral ulcers, and pleuritis. Labs: ANA 1:640 (homogeneous), anti-dsDNA positive, C3 low, C4 low, proteinuria 3.5 g/day. Renal biopsy shows mesangial and subendothelial deposits with wire-loop lesions. Which WHO/ISN class of lupus nephritis does this represent?
- A Class II (Mesangial proliferative)
- B Class III (Focal proliferative)
- C Class IV (Diffuse proliferative) ✓
- D Class V (Membranous)
Correct answer: C. Class IV (Diffuse proliferative)
Explanation
Wire-loop lesions on renal biopsy represent massive subendothelial immune complex deposits causing thickening of the capillary walls, a hallmark of ISN/RPS Class IV (diffuse proliferative) lupus nephritis, the most severe form involving more than 50% of glomeruli. It is associated with active urinary sediment, heavy proteinuria, and hypocomplementemia. Treatment is with high-dose glucocorticoids plus mycophenolate mofetil or cyclophosphamide.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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