Abetalipoproteinemia | Anatomy2Medicine
Acanthocytes

Abetalipoproteinemia

    • Abetalipoproteinemia
      • Autosomal-recessive deficiency in apoB-100 ,apoB-48
        • apoB-100 (binds LDL receptor; mediates VLDL secretion)
        • apoB-48 (mediates chylomicron secretion)
      • They can’t synthesize lipoproteins.

 

  • Sx appear in 1st months of life:
  • FTT, steatorrhea

 

      • acanthocytosis (= RBC with spikes, “spur cells,” membrane lipids messed up = puckered / spiky membrane)

 

  • ataxia
  • night blindness

 

Acanthocytosis

 

 

      • apoB-100 (binds LDL receptor; mediates VLDL secretion)

 

      • apoB-48 (mediates chylomicron secretion)

How to remember Apolipoproteins

  • A-I ActivatesLacat

 

 

  • B-100-Binds to LDL receptor mediates VLDL secretion

 

 

  • C-II –cofactor for lipoprotein lipase.

 

  • b-48– mediates chylomicrone secretion ( Chylomicron is dietary , so instead of 24 hours eating , hungry guy dreams 48 hours eating ).

 

 

  • E- mediates Extra – remnant- uptake

 

 

Exam MCQ

An 11 year old boy presents with balance and difficulty with night vision. His mother says he had foul smelling stools and failure to thrive as an infant. Physical examination reveals poor muscle coordination, ataxia, decreased proprioception and vibratory sensation. Lab tests show low total cholesterol and Vitamin A levels. The patient most likely has an inherited mutation in which of the following?

  1. 7- alpha hydroxylase
  2. Microsomal Transfer Protein (MTP)
  3. Hormone Sensitive Lipase (HSL)
  4. Lipoprotein Lipase (LPL)
  5. Lecithen Cholesterol acetyltransferase (LCAT)

 

Ans B

Microsomal Transfer Protein (MTP). The patient has Abetalipoproteinemia due to mutation in MTP 1. Microsomal Triglyceride Transfer Protein functions to transfer triglycerides to Apolipoprotein B during VLDL assembly in liver.

 

Clinical point :

Microsomal triglyceride transfer protein Inhibitors (MTP-I) represent a new class of cholesterol and triglyceride lowering agents with the ability to affect the production of lipoproteins in both the liver and intestine.