TTR and Familial transthyretin-related amyloidosis: In the most common forms of amyloidosis in Western Countries, the heart is frequently involved: immunoglobulin light chain amyloidosis (AL) due to clonal plasma cell dyscrasia, and transthyretin amyloidosis (ATTR), due to anomalies of transthyretin (TTR), which includes the most frequent acquired wild-type form (ATTRwt), where protein misfolding is age-related, and the hereditary variant form (ATTRv) where transthyretin is mutated.