Spleen visualization in both TTR and AL amyloidosis during 99mTc-DPD scintigraphy. Do we have to deal with a different than the myocardial uptake mechanism?

Technetium-99m- diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) is currently used in Europe for the diagnosis of cardiac amyloidosis, being able to distinguish light chain (AL) from transthyretin (TTR) type. We are reporting obvious spleen visualization in two patients suffering the first from proven TTR and the second from AL type of cardiac amyloidosis, with myocardial uptake-as anticipated-only in the first one. We raise the hypothesis that a common uptake mechanism exists for the spleen amyloid regardless of the type of the disease (AL or TTR), and is possibly different than the cardiac uptake mechanism.