A 58-year-old man with multiple myeloma develops progressive macroglossia and periorbital purpura. Biopsy of a rectal nodule shows amorphous eosinophilic deposits in vessel walls that stain with Congo red and exhibit apple-green birefringence under polarized light. The deposited material in this setting is composed of:

• A Serum amyloid A protein
• B Transthyretin
• C Beta-2 microglobulin
• D Immunoglobulin light chain fragments ✓

Explanation

AL amyloidosis complicating plasma cell myeloma results from deposition of fragments of monoclonal kappa or lambda light chains produced by the neoplastic clone. Serum amyloid A defines secondary reactive amyloidosis, beta-2 microglobulin underlies dialysis-related amyloidosis, and transthyretin causes familial forms and senile cardiac amyloidosis, none of which arise from a clonal plasma cell disorder.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.