TTR and primary systemic amyloidosis: The common proteins involved in systemic amyloidosis and organ dysfunction are immunoglobulin (Ig) LCs (AL), Ig heavy chain (AH), transthyretin (ATTR), serum amyloid A (AA), apolipoprotein A-I (AApoAI), β2-microglobulin, and leukocyte chemotactic factor-2 (ALECT2)3.