A 55-year-old man with longstanding rheumatoid arthritis develops nephrotic syndrome. Renal biopsy stained with Congo Red shows apple-green birefringence under polarized light in the mesangium and vessel walls. Immunohistochemistry identifies serum amyloid A (SAA) protein in the deposits. This is best classified as:
- A AL amyloidosis from plasma cell dyscrasia
- B ATTR amyloidosis from transthyretin mutation
- C AA amyloidosis secondary to chronic inflammation ✓
- D Beta-2 microglobulin amyloidosis from dialysis
Correct answer: C. AA amyloidosis secondary to chronic inflammation
Explanation
AA amyloidosis is a reactive (secondary) systemic amyloidosis caused by deposition of serum amyloid A (SAA) protein — an acute phase reactant produced by the liver in chronic inflammatory states. It complicates long-standing inflammatory conditions including RA, ankylosing spondylitis, IBD, and chronic infections (TB, osteomyelitis). The kidney is the most commonly affected organ, causing proteinuria and nephrotic syndrome. The amyloid fibrils show the classic Congo red apple-green birefringence.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.