TTR and amyloidosis: More than 98% of currently diagnosed CA results from fibrils composed of monoclonal immunoglobulin light chains (AL) or transthyretin (ATTR), a serum transport protein for thyroid hormone and retinol that is synthesized primarily by the liver; ATTR amyloidosis is further subtyped in hereditary (ATTRv) or acquired (ATTRwt or wildtipe) form.