99m Tc-PYP Uptake in an Insulin Ball

Long-term subcutaneous insulin injection causes histopathological changes, such as insulin amyloidosis resulting in poor glycemic control, at the insulin injection site. Insulin amyloidosis often leads to the formation of a nodule called the "insulin ball." An insulin ball has not yet been documented on 99m Tc-PYP scintigraphy. Hereby, we describe the case of a 74-year-old man with insulin-requiring diabetes who developed heart failure with preserved ejection fraction due to new-onset atrial fibrillation. 99m Tc-PYP scintigraphy for cardiac amyloidosis screening showed no tracer uptake in the myocardium but did show uptake in the insulin ball suspected by CT and MRI scans.