TTR and primary systemic amyloidosis: Systemic amyloidosis is a multiorgan disorder characterized by deposition of insoluble, toxic, fibrillary protein aggregates in the extracellular matrix.[1] Hereditary amyloidosis is an autosomal dominantly inherited disease that is associated with genetic variants of various genes, including transthyretin (TTR), fibrinogen A α-chain (Fib), apolipoprotein AI (ApoAI), apolipoprotein AII (ApoAII), lysozyme (Lys), cystatin C (Cys), gelsolin (Gel), and beta-2-microglobulin (β2-MG).