[Familial alpha lipoprotein deficiency. Tangier disease, familial hypoalphalipoproteinemia and familial deficiency of lecithin cholesterol acyltransferase deficiency].

The plasma lipoproteins are a group of macromolecules all of which transport lipids, including cholesterol, triglyceride and phospholipid, and all of which have one or more protein constituents, called apoproteins. It is becoming apparent that the apoproteins play an important role in lipoprotein metabolism. Recently the so called "alpha hypothesis" has been proposed, according to which a protective role for HDL in atherosclerosis has been postulated. Three "experiments of nature", characterized by deficiencies of HDL as genetic disorders, namely Tangier disease, familial hypoalphalipoproteinemia, familial lecithin: cholesterol acetyltransferase deficiency, support the "alpha hypothesis". The first italian cases with the genetic disorders are presented.