Mistaken Identity: Using Bone Scintigraphy to Diagnose Cardiac Amyloidosis in Patients With a Monoclonal Gammopathy

Cardiac amyloidosis (CA) occurs when amyloid fibrils infiltrate the myocardial interstitium, resulting in stiffened myocardium and a restrictive cardiomyopathy. More than 95% of CA is due to systemic light chain amyloidosis (AL) or transthyretin amyloidosis (ATTR). AL amyloidosis arises from a clonal plasma cell dyscrasia that produces amyloidogenic monoclonal immunoglobulins.

These immunoglobulins then misfold and deposit in various organs, such as the heart, kidneys, liver, gastrointestinal tract, and peripheral nerves. ATTR amyloidosis arises when transthyretin, a liver-derived transporter of thyroid hormone and retinol proteins, undergoes tetramer dissociation, misfolds, and forms amyloid fibrils in various distant organs.