A 34-year-old woman with known SLE presents with a serum creatinine that has risen from 0.8 to 2.4 mg/dL over 3 months. Urinalysis shows RBC casts, 3+ proteinuria. Anti-dsDNA antibodies are 480 IU/mL (very high), complement C3 is 48 mg/dL (low). Renal biopsy shows endocapillary and mesangial proliferation with subendothelial immune deposits and wire-loop lesions. What is the WHO/ISN class of this lupus nephritis?
- 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 are the hallmark of ISN/RPS Class IV diffuse proliferative lupus nephritis, which involves >50% of glomeruli. Subendothelial deposits and wire-loop lesions result from massive immune complex deposition. Class IV is the most severe and most common form of lupus nephritis, associated with nephritic syndrome, declining renal function, hypocomplementemia, and high anti-dsDNA titers. Treatment requires induction with high-dose corticosteroids plus cyclophosphamide (NIH regimen) or mycophenolate mofetil.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.