TTR and amyloidosis: Two ATTR amyloidosis subtypes are described, based on the pathophysiology and the type of amyloid fibrils that deposit in tissues: the wild-type ATTR (ATTRwt) amyloidosis, caused by the deposit of native transthyretin, and the hereditary ATTR (hATTR) amyloidosis, also known as ATTRv (v for variant) amyloidosis, caused by the deposit of both variant and wild-type transthyretin.