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CASE STUDY
A 42-year-old woman has heterozygous familial hypercholesterolemia (HeFH) but is otherwise well and has no symptoms of coronary or peripheral vascular disease. A carotid ultrasound was normal. Her mother had a myocardial infarction at age 51 and had no known risk factors other than her presumed HeFH. The patient also has elevated lipoprotein (a) at 2.5 times normal and low HDL-C (43 mg/dL). She developed muscle symptoms with each of 3 statins (atorvastatin, rosuvastatin, and simvastatin) so they were discontinued although she did not develop elevated levels of creatine kinase. Her untreated LDL-C is 235 mg/dL and triglycerides 125 mg/dL. Her LDL-C goal for primary prevention of arteriosclerotic vascular disease is in the 70-mg/dL range because of her multiple lipoprotein risk factors and her mother’s history of premature coronary artery disease. She has no other risk factors and her diet and exercise habits are excellent. How would you manage this patient?
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Plasma lipids are transported in complexes called lipoproteins. Metabolic disorders that involve elevations in any lipoprotein species are termed hyperlipoproteinemias or hyperlipidemias. Hyperlipemia denotes increased levels of triglycerides.
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The major clinical sequelae of hyperlipidemias are acute pancreatitis and atherosclerosis. The former occurs in patients with marked hyperlipemia. Control of triglycerides can prevent recurrent attacks of this life-threatening disease.
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Atherosclerosis is the leading cause of death for both genders in the USA and other Western countries. Lipoproteins that contain apolipoprotein (apo) B-100 convey lipids into the artery wall. These are low-density (LDL), intermediate-density (IDL), very-low-density (VLDL), and lipoprotein(a) (Lp[a]). Remnant lipoproteins formed during the catabolism of chylomicrons that contain the B-48 protein (apo B-48) can also enter the artery wall, contributing to atherosclerosis.
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Cellular components in atherosclerotic plaques (atheromas) include foam cells, which are transformed macrophages, and smooth muscle cells filled with cholesteryl esters. These cellular alterations result from endocytosis of modified lipoproteins via at least four species of scavenger receptors. Chemical modification of lipoproteins by free radicals creates ligands for these receptors. The atheroma grows with the accumulation of foam cells, collagen, fibrin, and frequently calcium. Whereas such lesions can slowly occlude coronary vessels, clinical symptoms are more frequently precipitated by rupture of unstable atheromatous plaques, leading to activation of platelets and formation of occlusive thrombi.
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Although treatment of hyperlipidemia can cause slow physical regression of plaques, the well-documented reduction in acute coronary events that follows vigorous lipid-lowering treatment is attributable chiefly to mitigation of the inflammatory activity of macrophages and is evident within 2–3 months after starting therapy.
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High-density lipoproteins (HDL) exert several antiatherogenic effects. They participate in retrieval of cholesterol from the artery wall and inhibit the oxidation of atherogenic lipoproteins. Low levels of HDL (hypoalphalipoproteinemia) are an independent risk factor for atherosclerotic disease and thus are a potential target for intervention.
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Cigarette smoking is a major risk factor for ...