Lipoprotein Disorders Microchapters
Editor-In-Chief: C. Michael Gibson, M.S., M.D. ; Associate Editor(s)-in-Chief: Rim Halaby, M.D. , Hardik Patel, M.D., Tarek Nafee, M.D. , Prince Tano Djan, BSc, MBChB , Aravind Kuchkuntla, M.B.B.S, Usama Talib, BSc, MD , Shivani Chaparala M.B.B.S , Vishal Devarkonda, M.B.B.S
Lipoproteins are aggregates of proteins and lipids that facilitate the circulation of hydrophobic lipids in the body. Disorders of lipids and lipoproteins metabolism have important health consequences, primarily on the cardiovascular system; however, may also affect the cerebrovascular system as well as the gastrointestinal system. Lipoprotein disorders can be described as abnormalities in the level of the lipids, which include cholesterol and triglycerides, or as abnormalities in the levels of lipoproteins that include LDL, HDL, VLDL and chylomicrons.
Lipoprotein disorders (also referred to as Lipid disorders, or Dyslipidemias, or Dyslipoproteinemias) were first classified in 1967 into different phenotypes by Fredrickson according to the type of lipoproteins that are affected. This approach is considered outdated for a number of reasons. Firstly, Friedrickson's classification failed to classify disorders of low lipids. Secondly, Fredrickson's classification of hyperlipoproteinemias took into consideration the elevation in chylomicrons, LDL, VLDL but did not include abnormalities in HDL levels. Other classifications have been suggested, one of which is the National Cholesterol Education Program (NCEP) classification of lipoprotein disorders. NCEP classifies lipid disorders according to laboratory cut off points for the levels of total cholesterol, LDL-C and HDL.
Lipoprotein disorders must be initially classified broadly into hypolipidemias and hyperlipidemias corresponding to low or high lipid levels, respectively. Each of these broad categories may be further classified into primary (genetic) causes or secondary environmental causes (e.g. substance abuse, medication use, lifestyle habits, or underlying diseases etc.). Secondary causes of lipid disorders are more common and thus must be ruled out before exploring primary causes of dyslipidemia.
Primary dyslipidemias are generally consistent in the way they affect the lipoproteins. Hyperlipoproteinemias generally cause elevations in the affected lipids/lipoproteins and hypolipoproteinemias generally cause reductions in the affected lipids/lipoproteins. Secondary dyslipidemias, on the other hand, may cause elevations in some lipoproteins and reductions in others. An example of this is the lipid profile in patients with diabetes mellitus, which commonly reveals a dyslipidemic triad consisting of elevated LDL and triglycerides with a concurrent reduction in HDL. In this case, diabetes mellitus and metabolic syndrome would be widely considered a hyperlipidemic disease due to the array of cardiovascular and cerebrovascular sequelae that arise consequent to the chronic hyperlipidemia associated with the disease. This is to say that in cases of mixed (elevated and decreased) findings on the lipid profile, clinicians must evaluate the secondary causes of the dysipidemia and manage the affected lipoproteins accordingly.
The table below summarizes is a list of primary lipoprotein disorders:
|Type of lipoprotein disorder||Genetic Lipoprotein Disorder||Gene Involved||Main Lipoprotein Involved|
|Hyperlipoproteinemias||Autosomal dominant hypercholesterolemia||PCSK9||LDL|
|Autosomal recessive hypercholesterolemia||ARH||LDL|
|Familial sitosterolemia||ABCG5 - ABCG8||LDL|
|Familial lipoprotein(a) hyperlipoproteinemia||Apo(a)||LDL|
|Familial defective apo B100||Apo B||LDL|
|Hepatic lipase deficiency||HL|
|Lipoprotein lipase deficiency||LPL||Chylomicron|
|Apo C-II deficiency||Apo C-II||Chylomicron|
|Apo A-V deficiency||Apo A-V deficiency||Chylomicron|
|Apo A-I deficiency||Apo A-I||HDL|
|Niemann-Pick disease||SMPD1, NPC1||HDL|
|Low LDL||Low HDL||Anemia,|
Chronic liver disease,
Chylomicron retention disease
Familial combined hypolipidemia
Apolipoprotein 1 deficiency,
Tangier disease, FISH eye disease, Familial combined hypolipidemia
|Type II||Type III:|
|Type V: |
Familial combined hyperlipidemia
- Musunuru K (2010). "Atherogenic dyslipidemia: cardiovascular risk and dietary intervention". Lipids. 45 (10): 907–14. doi:10.1007/s11745-010-3408-1. PMC 2950930. PMID 20524075.
- Nesto RW (2005). "Beyond low-density lipoprotein: addressing the atherogenic lipid triad in type 2 diabetes mellitus and the metabolic syndrome". Am J Cardiovasc Drugs. 5 (6): 379–87. PMID 16259526.