A 75-year-old man with heart failure undergoes myocardial biopsy. Deposits stain with Congo red and show apple-green birefringence. Mass spectrometry identifies wild-type transthyretin as the fibril protein. This form of amyloidosis is best classified as:
- A AL amyloidosis associated with plasma cell dyscrasia
- B AA amyloidosis secondary to chronic inflammation
- C Senile systemic amyloidosis derived from normal transthyretin ✓
- D Beta-2 microglobulin amyloidosis of long-term dialysis
Correct answer: C. Senile systemic amyloidosis derived from normal transthyretin
Explanation
Senile systemic amyloidosis results from deposition of structurally normal wild-type transthyretin, predominantly affecting the atria and ventricles of elderly men, with a slowly progressive restrictive cardiomyopathy. It must be distinguished from hereditary ATTR variants (mutated transthyretin) and from AL amyloidosis, where mass spectrometry would identify monoclonal light chains. Beta-2 microglobulin amyloid affects joints and bone in patients on long-term hemodialysis.
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.