Electron microscopy of a renal biopsy from a 35-year-old woman with nephrotic syndrome and SLE shows subendothelial and mesangial immune complex deposits, with tubuloretiuclar inclusions in endothelial cells. Light microscopy shows a 'tram-track' pattern on silver stain. What is the WHO/ISN-RPS classification of this lupus nephritis?

• A Class II (mesangial proliferative lupus nephritis)
• B Class III (focal lupus nephritis)
• C Class IV (diffuse lupus nephritis) ✓
• D Class V (membranous lupus nephritis)

Explanation

Class IV (diffuse lupus nephritis) shows subendothelial immune complex deposits involving >50% of glomeruli, producing the 'wire-loop' appearance on H&E/silver stains due to circumferential subendothelial deposits that thicken the capillary wall. The tram-track pattern on silver stain reflects mesangial interposition or new basement membrane formation. Tubuloreticular inclusions in endothelial cells are a hallmark of interferon-alpha elevation in SLE. This is the most severe form, associated with heavy proteinuria, active urinary sediment, and worst renal prognosis if untreated. Class V shows pure subepithelial (membranous) 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.