Hyperlipoproteinemia may be characterized by hypercholesterolemia, isolated hypertriglyceridemia, or both (Table 189-1). Diabetes mellitus, obesity, ethanol consumption, oral contraceptives, glucocorticoids, renal disease, hepatic disease, and hypothyroidism can cause secondary hyperlipoproteinemias or worsen underlying hyperlipoproteinemic states.
TABLE 189-1CHARACTERISTICS OF CLASSIC HYPERLIPIDEMIAS |Favorite Table|Download (.pdf) TABLE 189-1CHARACTERISTICS OF CLASSIC HYPERLIPIDEMIAS
| || ||Lipoproteins || |
|Lipid Phenotype ||Plasma Lipid Levels, mmol/L (mg/dL) ||Elevated ||Phenotype ||Clinical Signs |
|Isolated Hypercholesterolemia || || || || |
|Familial hypercholesterolemia ||Heterozygotes: total chol = 7–13 (275–500) ||LDL ||IIa ||Usually develop xanthomas in adulthood and vascular disease at 30–50 years |
| ||Homozygotes: total chol >13 (>500) ||LDL ||IIa ||Usually develop xanthomas and vascular disease in childhood |
|Familial defective apo B-100 ||Heterozygotes: total chol = 7–13 (275–500) ||LDL ||IIa || |
|Polygenic hypercholesterolemia ||Total chol = 6.5–9.0 (250–350) ||LDL ||IIa ||Usually asymptomatic until vascular disease develops; no xanthomas |
|Isolated Hypertriglyceridemia || || || || |
|Familial hypertriglyceridemia ||TG = 2.8–8.5 (250–750) (plasma may be cloudy) ||VLDL ||IV ||Asymptomatic; may be associated with increased risk of vascular disease |
|Familial lipoprotein lipase deficiency ||TG >8.5 (>750) (plasma may be milky postprandially) ||Chylomicrons ||I, V ||May be asymptomatic; may be associated with pancreatitis, abdominal pain, hepatosplenomegaly |
|Familial apo CII deficiency ||TG >8.5 (>750) (plasma may be milky postprandially) ||Chylomicrons ||I, V ||As above |
|Hypertriglyceridemia and Hypercholesterolemia || || || |
|Combined hyperlipidemia || |
TG = 2.8–8.5 (250–750)
Total chol = 6.5–13.0 (250–500)
|VLDL, LDL ||IIb ||Usually asymptomatic until vascular disease develops; familial form may also present as isolated high TG or an isolated high LDL cholesterol |
|Dysbetalipoproteinemia || |
TG = 2.8–5.6 (250–500)
Total chol = 6.5–13.0 (250–500)
|VLDL, IDL; LDL normal ||III ||Usually asymptomatic until vascular disease develops; may have palmar or tuberoeruptive xanthomas |
Standard lipoprotein analysis assesses total cholesterol, HDL cholesterol, and triglycerides with a calculation of LDL cholesterol levels using the following equation: LDL cholesterol = total cholesterol – HDL cholesterol – (triglycerides/5). The LDL cholesterol concentration can be estimated using this method only if triglycerides are <4.0 mmol/L (<350 mg/dL). Both LDL and HDL cholesterol levels are temporarily decreased for several weeks after myocardial infarction or acute inflammatory states, but can be accurately measured if blood is obtained within 8 h of the event.
Elevated levels of fasting plasma total cholesterol [>5.2 mmol/L (>200 mg/dL)] in the presence of normal levels of triglycerides are almost always associated with increased concentrations of plasma LDL cholesterol. A rare individual with markedly elevated HDL cholesterol may also have increased plasma total cholesterol levels. Elevations of LDL cholesterol can result from single-gene defects, from polygenic disorders, or from the secondary effects of other disease states.
FAMILIAL HYPERCHOLESTEROLEMIA (FH)
FH is a codominant genetic disorder due to mutations in the gene for the LDL receptor. Plasma LDL levels are elevated at birth and remain so throughout life. In untreated heterozygous adults, total cholesterol levels range from 7.1 to 12.9 mmol/L (275–500 ...