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For further information, see CMDT Part 28-01: Lipid Abnormalities

Key Features

Essentials of Diagnosis

  • Elevated serum total cholesterol or low-density lipoprotein (LDL) cholesterol, low serum high-density lipoprotein (HDL) cholesterol, or elevated serum triglycerides

  • Usually asymptomatic

  • In severe cases associated with metabolic abnormalities, superficial lipid deposition occurs

General Considerations

  • Cholesterol and triglycerides are the two main circulating lipids

  • Elevated levels of LDL cholesterol are associated with increased risk of atherosclerotic heart disease

  • High levels of HDL cholesterol are associated with lower risk of atherosclerotic heart disease

  • Non-HDL cholesterol

    • Increasingly recognized as an important measure of the total quantity of apolipoprotein B–containing atherogenic lipid particles

    • Calculated as Total cholesterol – HDL cholesterol

    • Advantages of non-HDL cholesterol

      • Less sensitive to fasting status

      • Better predictor of cardiovascular risk compared to LDL cholesterol

  • Lipoprotein(a)

    • A subfraction of LDL that is largely genetically determined

    • Has been recognized as a casual factor for atherosclerosis

    • Used as a risk enhancing factor favoring early statin treatment

    • May be useful to measure in patients with a strong family history or with early signs of early atherosclerotic cardiovascular disease (ASCVD)

    • Values > 50 mg/dL or > 100 nmol/L are considered elevated

    • The 2019 European Society of Cardiology/European Atherosclerosis Society (ESC/EAS) guidelines recommend one-time lipoprotein(a) measurement for all adults to identify those with very high values (> 180 mg/dL or > 430 nmol/L)

  • Assigning a "normal" range for serum lipids can be difficult because mean values vary across the world

    • Mean LDL cholesterol levels are currently declining in the United States, including in youths

    • There is no evidence currently available that adult cholesterol levels can be "too low"

  • Familial hypercholesterolemia

    • Genetic disorder

    • Rare in the homozygous state

    • Causes markedly high LDL levels and early cardiovascular disease (CVD)

Demographics

  • More common in men than women before age 50

  • More common in women than men after age 50

  • More common in whites and Hispanics than among blacks

Clinical Findings

Symptoms and Signs

  • No specific symptoms or signs

  • Eruptive xanthomas

    • Characterized by red-yellow papules, especially on the buttocks

    • Caused by extremely high levels of chylomicrons or VLDL particles (triglyceride level > 1000 mg/dL or 10 mmol/L)

  • Tendinous xanthomas

    • Caused by high LDL concentrations

    • Occur in certain tendinous areas (Achilles, patella, back of the hand)

    • Usually indicate one of the underlying genetic hyperlipidemias

  • Lipemia retinalis

    • Characterized by cream-colored blood vessels in the fundus

    • Caused by extremely high triglyceride levels (> 2000 mg/dL or 20 mmol/L)

Differential Diagnosis

eTable 28–1.Secondary causes of lipid abnormalities.

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