Medicine & USMLE

Familial Dysbetalipoproteinemia

  1. Chylomicron Metabolism
  2. VLDL Metabolism
  3. HDL Metabolism
  4. Abetalipoproteinemia
  5. Familial Hyperchylomicronemia
  6. Familial Hypercholesterolemia
  7. Familial Dysbetalipoproteinemia
  8. Familial Hypertriglyceridemia


Familial dysbetalipoproteinemia is also known as type III hyperlipoproteinemia. It’s an autosomal recessive disorder that is caused by a deficiency of apolipoprotein E. Apo E normally clears chylomicron remnants and IDL from the circulation, so a mutation here leads to an elevation of these lipoproteins. It is this increase in cholesterol-rich remnants that contributes to the premature atherosclerosis seen in the disease. The disease is also characterized by high triglyceride levels, and it may have findings such as palmar crease xanthomas.

Key Points

  • Familial Dysbetalipoproteinemia
    • Also known as type III hyperlipoproteinemia
    • Genetics
      • Autosomal recessive
    • Pathophysiology
      • Defective apolipoprotein E
        • Insufficient clearance leads to high levels of cholesterol-rich remnants
          • IDL (VLDL remnant)
          • Chylomicron remnants
        • Also increases triglycerides
          • This mechanism is more complex / not easily explained
    • Clinical Features
      • Premature atherosclerosis
        • Caused by increased plasma levels of cholesterol-rich remnants
        • May lead to cardiovascular complications, such as myocardial infarction, in young patients
      • Palmar (crease) xanthomas
      • Tuberoeruptive xanthomas
        • These are xanthomas that have an inflammatory component
        • This is less specific / classic than palmar crease xanthomas are