A 65-year-old man with long-standing multiple myeloma develops progressive nephrotic syndrome. Congo red staining of renal biopsy shows apple-green birefringence under polarized light in the mesangium and vessel walls. The amyloid protein in this clinical context is:

• A AA amyloid (serum amyloid A protein)
• B ATTR amyloid (transthyretin)
• C AL amyloid (immunoglobulin light chains) ✓
• D Aβ2M amyloid (beta-2 microglobulin)

Explanation

Multiple myeloma produces excess immunoglobulin light chains (usually lambda or kappa); these are deposited as AL amyloid (primary amyloidosis) which is the most common systemic amyloidosis in developed countries. AA amyloid derives from serum amyloid A in chronic inflammatory states (reactive amyloidosis). ATTR amyloid is associated with age-related and hereditary cardiac amyloidosis; Aβ2M amyloid occurs in dialysis patients.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.