NPPA and amyloidosis: Less common forms of amyloidosis are the AA (formerly called secondary) which is a result of chronic inflammatory conditions affecting mostly the liver and kidneys with less than 2% of the cases involving the heart and the isolated atrial amyloid where atrial natriuretic peptide (ANP) is synthesized by atrial myocytes and can be deposited as amyloid and is nowadays considered part of the ATTR or SSA subtypes.