Hyperlipidemia due to hepatic triacylglycerol lipase deficiency is a rare, genetic hyperalphalipoproteinemia characterized by elevated plasma cholesterol and triglyceride (TG) levels with a marked TG enrichment of low- and high-density lipoproteins (HDL), presence of circulating beta-very low density lipoproteins and elevated HDL cholesterol levels, in the presence of a very low, or undetectable, postheparin plasma hepatic lipase activity. Premature atherosclerosis and/or coronary heart disease may be associated.