Lipoprotein disorders

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Survival
Guide

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Lipoprotein Disorders Microchapters

Patient Information

Overview

Causes

Classification

Hyperlipoproteinemia
Hypolipoproteinemia

Treatment

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:  Rim Halaby, M.D. [2], Hardik Patel, M.D., Tarek Nafee, M.D. [3], Prince Tano Djan, BSc, MBChB [4], Aravind Kuchkuntla, M.B.B.S[5], Usama Talib, BSc, MD [6], Shivani Chaparala M.B.B.S [7], Vishal Devarkonda, M.B.B.S[8]

Synonyms and keywords:

## Overview

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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 This approach is considered outdated for a number of reasons.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 the 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.[1][2] 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.[2] 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.

## Causes

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For a complete list of causes of hyperlipoproteinemia click here.
For a complete list of causes of hypolipoproteinemia click here.

The table below summarizes is a list of primary lipoprotein disorders:

Type of lipoprotein disorder  | Genetic Lipoprotein Disorder | Gene Involved | Main Lipoprotein Involved

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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
Hypolipoproteinemias | Familial hypoalphalipoproteinemia |  |
GPIHBP1 deficiency | GPIHBP1 | Chylomicron
Apo A-I deficiency | Apo A-I | HDL
CETP deficiency | CETP | HDL
Niemann-Pick disease | SMPD1, NPC1 | HDL

## Classification

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| Lipid disorders|

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| Hypolipoproteinemia|

| Hyperlipoproteinemia

| Primary|

| Secondary|

| Primary|

| Secondary|

Low LDL|

| Low HDL|

| Anemia,
Chronic inflammation,
Chronic liver disease,
Hyperthyroidism,
Infection,
Malabsorption,
Malignancy,
Criticial illness,
More Causes...|

| Alcohol,
Diabetes,
Drugs,
Liver disease,
Obesity,
Renal disease,
Smoking,
Hypothyroidism
More Causes...

Abetalipoproteinemia
Hypobetalipoproteinemia
PCSK9 deficiency
Chylomicron retention disease
Familial combined hypolipidemia|

| LCAT deficiency,
Apolipoprotein 1 deficiency,
Familial hypoalphalipoproteinemia,
Tangier disease, FISH eye disease, Familial combined hypolipidemia|

| Type I:
Familial hyperchylomicronemia|

| Type II|

| Type III:
Dysbetalipoproteinemia|

| Type IV:
Primary hypertriglyceridemia

| Type V:
Mixed hyperlipoproteinemia|

| Type A:
Familial hypercholesterolemia|

| Type B:
Familial combined hyperlipidemia

## Treatment

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* To view detailed treatment of dyslipidemia click here.

## References

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1. ↑ 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.
2. ↑ 2.0 2.1 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.

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Lipopedia

Basic Science|

Cholesterol • Triglyceride

Lipoprotein metabolism and transport

Lipoprotein: Chylomicron • Chylomicron remnant • HDL • IDL • LDL • Lipoprotein(a) • VLDL • Lipoprotein-X

Apolipoprotein: APOA (1, 2, 4,  5) • APOB ( Apolipoprotein B-48, Apolipoprotein B-100) • APOC (1, 2, 3, 4) • APOD • APOE • APOH • APOJ • APOL • APOM • Apo(a)

Lipoprotein receptor: LDL receptor • Soluble low density lipoprotein receptor-related protein (sLRP) • Apolipoprotein E Receptor 2 • Scavenger receptor • Scavenger receptor A • Scavenger receptor B • VLDL receptor

Lipoprotein enzymes: Lipoprotein lipase • Lipoprotein-associated phospholipase A2 (Lp-PLA2) • Cholesterylester transfer protein ( Acetyl-CoA C-acyltransferase, Lecithin-cholesterol acyltransferase) • Microsomal triglyceride transfer protein • ABCA1

Genes: Low density lipoprotein receptor gene family • Microsomal triglyceride transfer protein • ABCA1

Lipoprotein Disorders|

Lipoprotein disorders

Primary lipoprotein disorders: Familial hyperchylomicronemia (Type I) • Familial hypercholesterolemia (Type IIA) • Familial combined hyperlipidemia (Type IIB) • Dysbetalipoproteinemia (Type III) • Primary hypertriglyceridemia (Type IV) • Mixed hyperlipoproteinemia (Type V)

Secondary lipoprotein disorders

Abnormal Laboratory Lipid Profile|

Low chylomicron • Low chylomicron remnant • Low HDL • Low IDL • Low LDL • Low lipoprotein(a) • Low VLDL

High chylomicron • High chylomicron remnant • High HDL • High IDL • High LDL • High Lipoprotein(a) • High VLDL
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