A 58-year-old man has periorbital purpura, macroglossia, and nephrotic-range proteinuria. Rectal biopsy shows amorphous eosinophilic material in vessel walls and around glands that stains with Congo red and displays apple-green birefringence under polarized light. Serum immunofixation reveals a monoclonal band. The amyloid fibrils in this patient are composed of:

• A Fragments of monoclonal immunoglobulin light chains, most commonly lambda ✓
• B Mutated transthyretin deposited in cardiac and nerve tissue
• C Amyloid A protein cleaved from serum amyloid-associated protein
• D Beta-2 microglobulin derived from chronic hemodialysis membranes

Explanation

AL amyloidosis complicates a plasma cell dyscrasia in which monoclonal light chain fragments form fibrils; lambda chains predominate over kappa. Mutated transthyretin causes hereditary familial amyloid polyneuropathy and cardiomyopathy, AA amyloid follows chronic inflammatory states, and beta-2 microglobulin causes dialysis-related amyloid with periarticular deposition. Periorbital purpura, macroglossia, and renal involvement together point to AL amyloidosis with a demonstrable monoclonal protein.

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.