A 30-year-old woman with SLE presents with serum creatinine rising from 0.8 to 2.1 mg/dL over 4 weeks. Urinalysis shows RBC casts and 3+ proteinuria. Renal biopsy reveals diffuse endocapillary proliferation with 'wire loop' lesions and subendothelial immune deposits by electron microscopy. This represents which ISN/RPS lupus nephritis class?

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

Explanation

Class IV diffuse lupus nephritis is characterized by involvement of >50% of glomeruli, endocapillary proliferation, 'wire loop' deposits (subendothelial deposits causing thickening of glomerular capillary walls), and is the most severe form. It presents with active urinary sediment (RBC casts), heavy proteinuria, and rapidly declining renal function. Class III is focal (<50% glomeruli); Class V shows membranous deposits without proliferation; Class II is mesangial only.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.