Apolipoprotein E (Apo-E) is a protein component of plasma lipoprotein that mediates the binding, internalization and catabolism of lipoprotein particles. Apo-E can serve as a ligand for the LDL (Apo-B/E) receptor and for the specific Apo-E receptor (chylomicron remnant) of hepatic tissues. Apo-E is present in all lipoprotein fractions in plasma and constitutes 10-20% of very low density lipoproteins (VLDL) and 1-2% of high density lipoproteins (HDL) . Apo-E is produced in most organs. Defects in Apo-E are a cause of hyperlipoproteinemia type III (lipid deposits in palms, tendons and elbows), sea-blue histiocyte disease (splenomegaly, thrombocytopenia), and lipoprotein glomerulopathy.