Lipoprotein-X in a Patient with Lymphoplasmacytic Sclerosing Cholangitis: An Unusual Cause of Secondary Hypercholesterolemia

Abstract

This paper presents an interesting case study of lymphoplasmacytic sclerosing cholangitis and a superb review of lipoprotein-X (Lp-X) with very high levels of total cholesterol and low-density lipoprotein (LDL) cholesterol by gel electrophoresis, and mild elevations in triglycerides, having resulted in the use of a statin (1). Fortunately, the patient had a low-normal apolipoprotein B (apoB), a more sensitive measure of atherogenic lipoprotein particles, questioning whether such statin treatment was necessary. As reviewed by the authors, this elevated measure of total cholesterol in a patient with marked cholestasis is measuring the cholesterol in both LDL and Lp-X. Lp-X is found clinically in adults with obstructive liver disease, whether intra- or extrahepatic. Phospholipids, which have no apoB, are excreted in the bile, and when there is cholestasis, they increase in the serum. Lp-X has more apolipoproteins A1, C, and E, more albumin in its core, and in the large case study cohorts cited in this article, have not been found to be atherogenic. This was also found in one of the original reports of 18 women with increased total cholesterol in primary biliary cirrhosis and illustrates the increasing phospholipid content and decreasing cholesterol ester/free cholesterol found in Lp-X (2). Because Lp-X has less apo B, it is less readily removed by the hepatic LDL receptor in the liver, with more removal through the reticuloendothelial system of the liver and spleen. In this case, a direct measure of LDL cholesterol was also very low, helping in