Apolipoprotien A1 deficiency is a rare monogenic metabolic disorder resulting in undetectable Apo A1 levels and HDL C less than 20mg/dl. APOA1 gene encodes for the Apo A1 protein which is the major component of HDL C. It is synthesized in the liver and released into the circulation as very small discoid pre beta HDL, which picks up free cholesterol from the cells and macrophages. Apo A1 also activates LCAT which esterifies free cholesterol on the surface of alpha 4 HDL resulting in the formation of cholesterol esters. These two initial steps in the reverse cholesterol are dependent on a functional Apo A1 which is defective in Apo A1 deficiency. Apo A1 synthesis is affected leading to very low HDL levels. Worldwide, 82 cases and a variety of mutations are reported. The biochemical phenotype is always a low Apo A1 and low HDL C. Clinical phenotype varies with each mutation and is inconsistent. Symptomatic patients usually present with corneal opacities, xanthelasma and premature heart disease. Cardiovascular risk assessment and optimizing risk factors has an important role in the management.
Apolipoprotein A deficiency
Apolipoprotein B deficiency
Lecithin cholesterol acyltransferase deficiency
Inborn errors of lipid metabolism
Inborn error of lipid metabolism
Lipid polymorphism
Low density lipoprotein physiology
Very low density lipoprotein physiology