A 58-year-old man with rheumatoid arthritis for 20 years develops nephrotic-range proteinuria and slowly rising creatinine. Renal biopsy shows amorphous eosinophilic material expanding the mesangium and glomerular capillary walls, with Congo red stain showing apple-green birefringence under polarized light. Immunofluorescence for serum amyloid A protein is strongly positive. Which statement is correct regarding this condition?
- A It is composed of lambda light chain fragments produced by a plasma cell dyscrasia
- B It is caused by transthyretin misfolding with senile systemic deposition
- C It is derived from serum amyloid A, an acute phase reactant, in chronic inflammatory states ✓
- D It is beta-2 microglobulin derived and restricted to long-term dialysis patients
Correct answer: C. It is derived from serum amyloid A, an acute phase reactant, in chronic inflammatory states
Explanation
Reactive systemic AA amyloidosis follows years of chronic inflammation such as rheumatoid arthritis, tuberculosis, or bronchiectasis, with fibrils formed from serum amyloid A, an acute phase protein made by the liver. Light chain AL amyloidosis is the answer if there were a monoclonal gammopathy or plasma cell dyscrasia, which is not described here. Transthyretin and beta-2 microglobulin amyloidoses involve heart and nerves or dialysis related arthropathy respectively rather than this setting.
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.