ApoAI (Apolipoprotein A1) is a major component of high density lipoprotein (HDL, the “good cholesterol”) in plasma. It is produced in the liver and small intestine. ApoA1 is a cofactor for lecithin cholesterolacyltransferase (LCAT) that is responsible for the formation of plasma cholesteryl esters and promotes cholesterol efflux from tissues to the liver for excretion. Defects in ApoA1 are associated with high density lipoprotein deficiency (HDLD) and systemic non-neuropathic amyloidosis.