Everything about Hyperlipoproteinemia Type Ii totally explained
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ICD9 = - |
DiseasesDB = 6255|
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Hyperlipidemia,
hyperlipoproteinemia or
dyslipidemia is the presence of raised or abnormal levels of
lipids and/or
lipoproteins in the
blood. Lipids (fatty molecules) are transported in a
protein capsule, and the density of the lipids and type of protein determines the fate of the particle and its influence on
metabolism.
Lipid and lipoprotein abnormalities are extremely common in the general population, and are regarded as a highly modifiable risk factor for
cardiovascular disease due to the influence of
cholesterol, one of the most clinically relevant lipid substances, on
atherosclerosis. In addition, some forms may predispose to
acute pancreatitis.
Classification
Hyperlipidemias are classified according to the
Fredrickson classification which is based on the pattern of lipoproteins on
electrophoresis or
ultracentrifugation. It was later adopted by the
World Health Organization (WHO). It doesn't directly account for
HDL, and it doesn't distinguish among the different
genes that may be partially responsible for some of these conditions. It remains a popular system of classification, but is considered dated by many.
Hyperlipoproteinemia type I
This very rare form (also known as
Buerger-Gruetz syndrome,
primary hyperlipoproteinaemia, or
familial hyperchylomicronemia) is due to a deficiency of
lipoprotein lipase (LPL) or altered
apolipoprotein C2, resulting in elevated
chylomicrons, the particles that transfer fatty acids from the
digestive tract to the
liver. Lipoprotein lipase is also responsible for the initial breakdown of endogenously made triacylglycerides in the form of very low density lipoprotein (VLDL). As such, one would expect a defect in LPL to also result in elevated VLDL. Its prevalence is 0.1% of the population.
Hyperlipoproteinemia type II
Hyperlipoproteinemia type II, by far the most common form, is further classified into type IIa and type IIb, depending mainly on whether there's elevation in the triglyceride level in addition to LDL cholesterol.
Type IIa
This may be sporadic (due to dietary factors), polygenic, or truly familial as a result of a mutation either in the
LDL receptor gene on
chromosome 19 (0.2% of the population) or the
ApoB gene (0.2%). The familial form is characterized by
tendon xanthoma,
xanthelasma and premature cardiovascular disease.
Type IIb
The high VLDL levels are due to overproduction of substrates, including triglycerides, acetyl CoA, and an increase in B-100 synthesis. They may also be caused by the decreased clearance of LDL. Prevalence in the population is 10%.
- Familial combined hyperlipoproteinemia (FCH)
- Secondary combined hyperlipoproteinemia (usually in the context of metabolic syndrome, for which it's a diagnostic criterion)
Treatment
While dietary modification is the initial approach, many patients require treatment with
statins (HMG-CoA reductase inhibitors) to reduce cardiovascular risk. If the triglyceride level is markedly raised,
fibrates may be preferable due to their beneficial effects. Combination treatment of statins and fibrates, while highly effective, causes a markedly increased risk of
myopathy and
rhabdomyolysis and is therefore only done under close supervision. Other agents commonly added to statins are
ezetimibe,
niacin and
bile acid sequestrants. There is some evidence for benefit of plant sterol-containing products and
ω3-fatty acids
Hyperlipoproteinemia type III
This form is due to high
chylomicrons and IDL (intermediate density lipoprotein). Also known as
broad beta disease or
dysbetalipoproteinemia, the most common cause for this form is the presence of
ApoE E2/E2 genotype. It is due to cholesterol-rich VLDL (β-VLDL). Prevalence is 0.02% of the population.
Hyperlipoproteinemia type IV
This form is due to high
triglycerides. It is also known as
hypertriglyceridemia (or
pure hypertriglyceridemia). According to the NCEP-ATPIII definition of high triglycerides (>200 mg/dl),
prevalence is about 16% of adult population.
Hyperlipoproteinemia type V
This type is very similar to type I, but with high
VLDL in addition to chylomicrons.
It is also associated with glucose intolerance and hyperuricemia
Unclassified forms
Non-classified forms are extremely rare:
Hypo-alpha lipoproteinemia
Hypo-beta lipoproteinemia (prevalence 0.01-0.1%)Further Information
Get more info on 'Hyperlipoproteinemia Type Ii'.
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