TTR and Familial transthyretin-related amyloidosis: Transthyretin Amyloidosis (ATTR) is a severe systemic and fatal disease caused by a misfolding and aggregation of the normal, non-mutated transthyretin protein (wild-type ATTR) or by a heterozygous mutation in the TTR gene (hereditary/variant ATTR) that promotes misfolding and aggregation.