TTR and cardiac amyloidosis: Perugini grade 0, which corresponds to no cardiac uptake of the bone tracer, makes the diagnosis of cardiac amyloidosis very unlikely; nevertheless, some mutations of the ATTR gene, such as Phe64Leu, may determine cardiomyopathy, even if bone scintigraphy does not show any cardiac uptake, requiring definitive histological confirmation if suspicion for ATTR-CM remains high [3,102].