A common gene has been proposed to be associated with LDL particles that are small and dense (phenotype B), which is distninct from phenotype A where the particles are larger and more buoyant (Fig. 6.13). Small, dense LDL particles are found in association with high-to-normal plasma triglyceride levels, increased levels of remnant lipoproteins, and reduced levels of a subclass of HDL. The genotype may interact with other genes that raise levels of lipids and apo B, to cause familial combined hyperlipidaemia.
