Genetic hyperlipidemia and atherosclerosis

Familial hypercholesterolemia is one of the several simply inherited forms of hyperlipidemia known to occur in man. In 1973, an important study of a large group of consecutively studied survivors of myocardial infarction by Goldstein and co-workers established that one out of five such survivors below age 60 had some form of simply inherited or monogenic hyperlipidemia. The nature of these disorders and their relationship to premature vascular disease is the focus of this review. The principal method for identifying monogenic hyperlipidemia is the ascertainment of lipid levels above statistically determined 95% cutoff limits in multiple family members. Studies of single cases can not always identify monogenic hyperlipidemia because only one out of five with such elevated levels are shown to have monogenic hyperlipidemia. In addition, only two disorders can be confidently diagnosed independent of lipid and lipoprotein data. These are familial hypercholesterolemia and familial lipoprotein lipase deficiency. Determination of lipoprotein phenotypes or 'typing' can be misleading from a genetic sense, since in familial combined hyperlipidemia multiple phenotypes are the rule, not the exception. Currently, the diagnoses of familial hypertriglyceridemia, familial Type V hyperlipoproteinemia, and familial hyperalphalipoproteinemia require family studies for ascertainment. Although familial Type III or dysbetalipoproteinemia or broad beta disease is strongly suggested by linear collections of lipid in palmar creases, this is not entirely pathognomonic.