A 65-year-old man with multiple myeloma develops nephrotic syndrome. Renal biopsy shows eosinophilic amyloid deposits that are apple-green birefringent under polarized light after Congo red staining. Mass spectrometry identifies the amyloid fibrils as AL-lambda type. What is the composition of AL amyloid?
- A Immunoglobulin light chains (most commonly lambda) or fragments thereof ✓
- B Serum amyloid A protein (SAA) derived from acute phase reaction
- C Beta-2 microglobulin from dialysis-associated amyloidosis
- D Transthyretin (TTR) from wild-type cardiac amyloidosis
Correct answer: A. Immunoglobulin light chains (most commonly lambda) or fragments thereof
Explanation
AL (amyloid light chain) amyloidosis is produced by plasma cell dyscrasias (myeloma, MGUS, Waldenstrom's) where free monoclonal immunoglobulin light chains (most commonly lambda > kappa) or their N-terminal fragments misfold into beta-pleated sheet amyloid fibrils. AL is the most common systemic amyloidosis in developed countries, affecting kidneys (nephrotic syndrome), heart (restrictive cardiomyopathy), and peripheral nerves. AA amyloid derives from SAA in chronic inflammation. TTR amyloid causes familial or senile (wild-type) cardiac amyloidosis.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.