Familial dyslipidemias

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Dyslipidemia	Protein defect	Elevated lipoproteins	Major manifestations
Familial chylomicronemia syndrome (type I)	Lipoprotein lipase, ApoC-2	Chylomicrons	Acute pancreatitis, Lipemia retinalis, Eruptive xanthomas
Familial hypercholesterolemia (type II A)	LDL receptor, ApoB-100	LDL	Premature atherosclerosis, Tendon xanthomas, Xanthelasmas
Familial dysbetalipoproteinemia (type III)	ApoE	Chylomicron & VLDL remnants	Premature atherosclerosis, Tuboeruptive & palmar xanthomas
Familial hypertriglyceridemia (type IV)	Polygenic	VLDL	Associated with coronary disease, pancreatitis & diabetes

• Type II
  • Premature atherosclerosis, may lead to myocardial infarction at a very young age (< 20 years)
  • Arcus lipoides corneae
  • Tuberous/tendon xanthomas (especially the Achilles tendon) in type IIa

Abetalipoproteinemia

• Etiology
  • Deficiency of apolipoproteins (ApoB-48, ApoB-100)
  • Due to a mutation in the microsomal triglyceride transfer protein (MTTP) gene
• Pathophysiology
  • Autosomal recessive disease
  • Deficiency of chylomicrons, VLDL, and LDL (hypolipoproteinemia)
• Clinical features
  • Early
    • Steatorrhea
    • Failure to thrive
    • Fat malabsorption → fat-soluble vitamin deficiency
• Diagnostics
  • Intestinal biopsy: Histology may reveal lipid-laden enterocytes.