Apolipoproteins and Lipoprotein Families in Familial Lecithin: Cholesterol Acyltransferase Deficiency

The plasma lipoprotein system in patients with familial LCAT deficiency contains all the polypeptides and lipoprotein families identified previously in plasma lipoproteins of normal subjects. There are, however, some qualitative and quantitative differences. The most significant qualitative difference is the presence in LCAT-deficient plasma of LP-X, the abnormal low density lipoprotein species characteristic of obstructive jaundice. The major quantitative difference is the reduced concentration of ApoA, ApoB, and ApoD in LCAT-deficient plasma. It has already been demonstrated that most lipoprotein species in LCAT deficiency have an abnormal lipid composition characterized by unusually high contents of unesterified cholesterol and lecithin and a negligible amount of esterified cholesterol (4). These abnormalities of the lipoprotein system in familial LCAT deficiency seem to result from the virtual absence of LCAT activity rather than from the absence of normally occurring lipoprotein families or their constitutive polypeptides.