A patient develops reactive amyloidosis (AA type) after 20 years of rheumatoid arthritis. On biopsy, which site is MOST commonly sampled to detect systemic AA amyloidosis early?
- A Bone marrow trephine biopsy
- B Rectal mucosa or abdominal fat pad aspiration (subcutaneous fat biopsy) ✓
- C Renal biopsy as the first diagnostic step
- D Endomyocardial biopsy
Explanation
Abdominal subcutaneous fat pad aspiration (fat pad biopsy) and rectal mucosa biopsy are the preferred minimally invasive screening sites for systemic amyloidosis because both sites have high sensitivity (fat pad ~80-85%, rectal ~75-80% for AL and AA amyloidosis) and virtually no morbidity. These sites are sampled first before resorting to renal, cardiac, or liver biopsy, which carry higher procedural risks. Bone marrow trephine may show amyloid deposits in plasma cell dyscrasia-associated AL amyloidosis but is less sensitive for AA. Endomyocardial biopsy is reserved for suspected cardiac amyloidosis when non-invasive imaging is inconclusive.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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