An 82-year-old man presents with progressive exertional dyspnea and biventricular heart failure. Endomyocardial biopsy shows amorphous eosinophilic interstitial deposits positive for Congo red. Mass spectrometry identifies a plasma protein synthesized primarily by the liver that transports thyroxine and retinol-binding protein. He has no monoclonal gammopathy and no chronic inflammatory disease. The most likely diagnosis is:

• A Beta-2 microglobulin amyloidosis related to renal failure
• B AL amyloidosis due to a kappa light-chain clone
• C AA amyloidosis secondary to occult osteomyelitis
• D Senile systemic amyloidosis due to wild-type transthyretin ✓

Explanation

Wild-type transthyretin (ATTRwt) produces senile systemic amyloidosis, typically affecting men older than 70 years with restrictive cardiomyopathy and frequently preceding carpal tunnel syndrome. Transthyretin is the hepatic carrier of thyroxine and retinol-binding protein, matching the stem. Absence of a monoclonal gammopathy excludes AL amyloidosis, absence of chronic inflammation excludes AA disease, and beta-2 microglobulin amyloidosis is restricted to long-term dialysis and targets joints rather than myocardium.

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.