A patient with SLE has a positive ANA, anti-dsDNA antibody, and low C3/C4. The Congo red stain of a renal biopsy would show apple-green birefringence ONLY if:

• A An associated monoclonal plasma cell dyscrasia deposits AL amyloid
• B Fibrinoid necrosis of vessels produces collagen-derived fibrils
• C Wire-loop lesions of lupus nephritis always contain amyloid material
• D Lupus nephritis progresses to AA amyloidosis from chronic inflammation ✓

Explanation

SLE itself does not directly produce amyloid deposits in the kidney (wire-loop lesions are subendothelial immune complex deposits, not amyloid). However, in longstanding SLE with persistent systemic inflammation, elevated SAA can lead to secondary AA amyloidosis, which would show apple-green birefringence with Congo red staining under polarised light. AL amyloidosis from a coincident plasma cell dyscrasia is a separate entity. Fibrinoid necrosis contains plasma proteins and fibrin, not amyloid fibrils. Wire-loop lesions are not amyloid.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.