Selective Cardiac Tc-99m DPD Retention With Markedly Reduced Extracardiac Uptake in Hereditary Transthyretin Amyloidosis.

We describe a case of a 76-year-old man with genetically confirmed hereditary transthyretin amyloidosis (hATTR) due to a pathogenic TTR variant, c.97_99dup (p.Met33dup), with possible coexisting amyloid light-chain (AL) amyloidosis. Serial Technetium-99m 2,3-dicarboxypropane-1,1-diphosphonate Tc-99m DPD) scintigraphy revealed persistent grade 3 myocardial uptake but minimal extracardiac tracer accumulation in the skeletal system and intestines. Despite similar or higher heart-to-contralateral (H/CL) ratios, other patients did not exhibit this pattern, underscoring the atypical nature of the observed findings in this case. This case highlights a rare myocardial-predominant uptake phenotype, which may offer insight into the distribution of bone-avid tracers in cardiac amyloidosis.