A 70-year-old man undergoes autopsy for heart failure of unknown etiology. The ventricles are thick-walled and firm with a waxy, rubbery cut surface. Congo red staining of myocardial tissue shows amorphous eosinophilic deposits that exhibit apple-green birefringence under polarized light. These deposits are composed of which protein?
- A Serum amyloid A (SAA)
- B Wild-type transthyretin (ATTR) ✓
- C Immunoglobulin light chains (AL)
- D Beta-2 microglobulin
Correct answer: B. Wild-type transthyretin (ATTR)
Explanation
Senile systemic amyloidosis in the elderly is caused by deposition of wild-type transthyretin (ATTR) in the myocardium, producing thick-walled rigid ventricles. AL amyloidosis (light chains) occurs with plasma cell dyscrasias. SAA is seen in secondary amyloidosis. Beta-2 microglobulin deposits in dialysis-related amyloidosis, primarily in joints.
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.