Discordance of 99mTc-PYP Uptake in the Myocardium and Breast Both Before and After Treatment in Transthyretin Cardiac Amyloidosis.

Scintigraphy using 99mTc-PYP as a bone-avid radiotracer reveals physiological and pathologic accumulation of the tracer in the extraosseous tissues and organs-including the breasts-in addition to the bones. 99mTc-PYP scintigraphy also reveals deposits of wild-type amyloid transthyretin (ATTRwt) in the myocardium and extracardiac sites, such as subcutaneous fat, skeletal trunk muscles, and alimentary tract, of patients with ATTRwt cardiomyopathy (CM). We describe an 87-year-old man with ATTRwt-CM in whom myocardial 99mTc-PYP uptake was reduced and mammary tracer uptake was increased due to gynecomastia after treatment with a disease-modifying drug for ATTRwt-CM, tafamidis, and heart failure medications, including spironolactone.