According to the ISN/RPS classification of lupus nephritis, what feature distinguishes class III from class IV lupus nephritis on renal biopsy?

• A Presence versus absence of wire-loop lesions
• B Involvement of fewer than 50% versus 50% or more of glomeruli ✓
• C Segmental versus global endocapillary proliferation within affected glomeruli
• D Absence versus presence of tubuloreticular inclusions on electron microscopy

Explanation

Class III denotes focal lupus nephritis affecting fewer than 50% of glomeruli, whereas class IV denotes diffuse disease involving 50% or more of glomeruli, regardless of whether lesions are segmental or global. Wire loops occur in both classes, so they cannot discriminate. Tubuloreticular inclusions reflect interferon exposure and are seen across classes. Activity and chronicity indices grade severity but do not define the class boundary.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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