Chapter 15 - Disorders of Cholesterol Metabolism: The Hyperlipoproteinaemias

Abstract

This chapter discusses the hyperlipoproteinemia types II and III, the two forms of hyperlipidemia that are of greatest significance from the point of view of the metabolism of cholesterol, with main emphasis on the familial forms of these disorders. Hyperlipidemia refers to a raised plasma concentration of cholesterol or triglyceride or of both. Although measurement of plasma total cholesterol and total triglyceride concentrations is essential as a first step in the diagnosis of a plasma lipid disorder, and may in some cases be adequate as a guide to treatment, it cannot give decisive information about the abnormal plasma lipoprotein pattern responsible for the hyperlipidaemia. It is, therefore, much more informative to consider a raised plasma lipid concentration as the expression of a raised concentration of one or more plasma lipoprotein fractions (hyperlipoproteinemia), defined in terms of cut-off points. The hyperlipoproteinemias are classified in accordance with the recommendations of the World Health Organization (WHO) into the six types. The abnormal lipoprotein patterns may be primary, or they may be secondary to one or other of the conditions listed by the WHO.