TTR and cardiac amyloidosis: Typically, amyloid cardiomyopathy, a progressive infiltrative condition, is caused by either misfolded monoclonal immunoglobulin light chains (ALs) from an abnormal clonal proliferation of plasma cells that exert direct toxic effects on myocytes or by the abnormal folding of transthyretin (TTR), a liver-synthesized protein (previously called prealbumin) that is involved in the transportation of the hormone thyroxine and retinol-binding protein.