TTR and amyloidosis: Transthyretin (TTR) amyloidosis (ATTR) is a rapidly progressive, debilitating, and fatal multisystem disease caused by misfolded TTR accumulating as toxic amyloid deposits in the nerves, heart, gastrointestinal tract, and musculoskeletal tissues.1, 2, 3 ATTR amyloidosis manifests with either cardiomyopathy (ATTR-CM), polyneuropathy, or both.1