A 35-year-old woman with SLE develops renal involvement. Renal biopsy shows endocapillary hypercellularity, wire-loop lesions, hyaline thrombi, and full-house immunofluorescence (IgG, IgA, IgM, C3, C1q). What WHO/ISN-RPS class does this represent, and what is its significance?

• A Class III (focal proliferative lupus nephritis) — affects fewer than 50% of glomeruli, moderate prognosis
• B Class V (membranous lupus nephritis) — presents with pure nephrotic syndrome, wire loops are characteristic
• C Class II (mesangial proliferative lupus nephritis) — mesangial deposits only, benign course
• D Class IV (diffuse proliferative lupus nephritis) — worst renal prognosis, requires aggressive immunosuppression ✓

Explanation

The biopsy findings of endocapillary hypercellularity (>50% of glomeruli), wire-loop lesions (subendothelial immune complex deposits that appear as thickened basement membranes), hyaline thrombi, and full-house immunofluorescence pattern are hallmarks of ISN/RPS Class IV (diffuse lupus nephritis), affecting ≥50% of glomeruli. This is the most severe and common form causing significant renal morbidity, presenting with nephritic syndrome, heavy proteinuria, hypertension and renal impairment. It carries the worst renal prognosis among lupus nephritis classes and requires aggressive treatment with cyclophosphamide or mycophenolate mofetil plus corticosteroids. Wire loops can also rarely appear in Class V, but full-house pattern with endocapillary hypercellularity points to Class IV.

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

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Written and medically reviewed by the StethoPrep medical team.