APOA1 and cutaneous mastocytosis: However, it is important to note that the radionuclide scan alone is not specific for ATTR-CM since ~40% with AL-CM have a positive radionuclide scan (including Perugini grade 2 or 3 positivity in ~10%) and cardiac apolipoprotein A-I amyloidosis is also associated with low grade cardiac uptake on Tc-DPD scintigraphy (8, 51).