AA amyloidosis (secondary amyloidosis) complicates chronic inflammatory diseases such as rheumatoid arthritis. The amyloid fibrils in AA amyloidosis are derived from which serum precursor protein?

• A Immunoglobulin light chains (kappa or lambda)
• B Beta-2 microglobulin accumulating in renal failure
• C Transthyretin (TTR) with age-related misfolding
• D Serum amyloid A (SAA), an acute phase reactant produced by the liver ✓

Explanation

AA amyloidosis is caused by deposition of fibrils derived from serum amyloid A (SAA), an acute phase reactant apolipoprotein produced by hepatocytes in large quantities during chronic inflammation. With sustained inflammation (RA, FMF, osteomyelitis, IBD), chronically elevated SAA provides a large pool for partial proteolytic cleavage into AA fragments that misfold and deposit in organs, predominantly the kidney, spleen, and liver. AL amyloidosis uses immunoglobulin light chains, dialysis-related amyloidosis uses β2-microglobulin, and senile systemic amyloidosis uses wild-type TTR.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.