TTR and prealbumin measurement: Lastly, genetic testing from peripheral blood revealed a missense mutation in the transthyretin (TTR) gene, leading to a replacement of thymine with guanine at nucleotide 381 (c.381T>G), ultimately substituting isoleucine for methionine in the TTR protein in amino acid 127 (p.Ile127Met), leading to the final diagnosis of a variant transthyretin amyloidosis (vATTR).