A renal biopsy from a patient with long-standing rheumatoid arthritis shows amyloid deposits that stain positively with Congo red and demonstrate apple-green birefringence under polarised light. Mass spectrometry would most likely identify the amyloid protein as:
- A Lambda light chain-derived AL amyloid
- B Wild-type transthyretin (ATTRwt)
- C SAA-derived AA amyloid ✓
- D Beta-2-microglobulin (Aβ2M)
Correct answer: C. SAA-derived AA amyloid
Explanation
Chronic inflammatory conditions such as rheumatoid arthritis, osteomyelitis, and IBD cause secondary (reactive) AA amyloidosis. Persistent inflammation drives hepatic overproduction of serum amyloid A (SAA), an acute-phase protein; SAA is proteolytically processed to AA protein that polymerises into amyloid fibrils, preferentially depositing in the kidneys, spleen, and liver.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.