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| ==[[Hyperlipidemia classification | Classification]]== | | ==[[Hyperlipidemia classification | Classification]]== |
| Hyperlipidemias are classified according to the '''[[Donald S. Fredrickson|Fredrickson]] classification''' which is based on the pattern of lipoproteins on [[electrophoresis]] or [[Ultracentrifuge|ultracentrifugation]].<ref>Frederickson DS, Lee RS. A system for phenotyping hyperlipidemia. ''Circulation'' 1965;31:321-7. PMID 14262568.</ref> It was later adopted by the [[World Health Organization]] (WHO). It does not directly account for [[High density lipoprotein|HDL]], and it does not 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.
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| {| border="1" cellpadding="5" cellspacing="0" align="center" class="sortable"
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| |+ '''Fredrickson classification of Hyperlipidemias'''
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| ! Hyperlipoproteinemia
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| ! Synonyms
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| ! Problems
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| ! Labs description
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| ! Treatment
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| ! Type I
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| | ''Buerger-Gruetz syndrome'', ''Primary hyperlipoproteinaemia'', or ''Familial hyperchylomicronemia''
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| | Decreased [[lipoprotein lipase]] (LPL) or altered [[apolipoprotein C2|ApoC2]]
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| | Elevated [[Chylomicrons]]
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| | Diet Control
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| ! Type IIa
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| | ''Polygenic hypercholesterolaemia'' or [[Familial hypercholesterolemia]]
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| | [[LDL receptor]] deficiency
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| | Elevated [[LDL]] only
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| | Bile Acid Sequestrants, [[Statin]]s, [[Niacin]]
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| ! Type IIb
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| | [[Combined hyperlipidemia]]
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| | Decreased [[LDL receptor]] and Increased [[apolipoprotein B|ApoB]]
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| | Elevated [[LDL]] and [[VLDL]] and Triglycerides
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| | [[Statin]]s, [[Niacin]], [[Gemfibrozil]]
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| ! Type III
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| | ''Familial Dysbetalipoproteinemia''
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| | Defect in [[apolipoprotein E|ApoE]] synthesis
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| | Increased [[IDL]]
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| | Drug of choice: [[Gemfibrozil]]
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| ! Type IV
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| | ''Endogenous Hyperlipemia''
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| | Increased [[VLDL]] production and Decreased elimination
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| | Increased [[VLDL]]
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| | Drug of choice: [[Niacin]]
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| ! Type V
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| | ''Familial Hypertriglyceridemia''
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| | Increased [[VLDL]] production and Decreased [[LPL]]
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| | Increased [[VLDL]] and [[Chylomicrons]]
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| | [[Niacin]], [[Gemfibrozil]]
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| |}
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| ===Hyperlipoproteinemia type I===
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| 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 [[chylomicron]]s, 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.
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| ===Hyperlipoproteinemia type II===
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| Hyperlipoproteinemia type II, by far the most common form, is further classified into type IIa and type IIb, depending mainly on whether there is elevation in the triglyceride level in addition to LDL cholesterol.
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| ====Type IIa====
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| {{main|Familial hypercholesterolemia}}
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| 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 [[apolipoprotein B|ApoB]] gene (0.2%). The familial form is characterized by [[Xanthoma|tendon xanthoma]], [[xanthelasma]] and premature cardiovascular disease.
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| ====Type IIb====
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| 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%.
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| * Familial combined hyperlipoproteinemia (FCH)
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| * Secondary combined hyperlipoproteinemia (usually in the context of [[metabolic syndrome]], for which it is a diagnostic criterion)
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| ====Treatment====
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| While dietary modification is the initial approach, many patients require treatment with [[statin]]s (HMG-CoA reductase inhibitors) to reduce cardiovascular risk. If the triglyceride level is markedly raised, [[fibrate]]s 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 sequestrant]]s. There is some evidence for benefit of plant sterol-containing products and [[omega-3 fatty acid|ω<sub>3</sub>-fatty acids]]<ref>Thompson GR. Management of dyslipidaemia. ''Heart'' 2004;90:949-55. PMID 15253984.</ref>
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| ===Hyperlipoproteinemia type III===
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| This form is due to high [[chylomicron]]s and IDL (intermediate density lipoprotein). Also known as ''broad beta disease'' or ''dysbetalipoproteinemia'', the most common cause for this form is the presence of [[Apolipoprotein E|ApoE]] E2/E2 genotype. It is due to cholesterol-rich VLDL (β-VLDL). Prevalence is 0.02% of the population.
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| ===Hyperlipoproteinemia type IV===
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| This form is due to high [[triglyceride]]s. It is also known as ''[[hypertriglyceridemia]]'' (or ''pure hypertriglyceridemia''). According to the NCEP-ATPIII definition of high triglycerides (>200 mg/dl),
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| prevalence is about 16% of adult population.<ref>Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) Final Report. ''Circulation'' 2002; 106; page 3240</ref>
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| ===Hyperlipoproteinemia type V===
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| This type is very similar to type I, but with high [[VLDL]] in addition to chylomicrons.
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| It is also associated with glucose intolerance and hyperuricemia
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| ==Unclassified forms==
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| Non-classified forms are extremely rare:
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| * Hypo-alpha lipoproteinemia
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| * Hypo-beta lipoproteinemia (prevalence 0.01-0.1%)
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| ==References== | | ==References== |