Hyperlipoproteinemia refers to abnormally elevated levels of any or all lipids and/or lipoproteins in the blood.
Mixed hypelipidemia is highly prevalent and characterized by elevated low density lipoprotein (LDL) cholesterol and triglyceride levels.
It is the most common form of dyslipidemias.
The incident of mixed hyper lipidemia is increasing due to the growing epidemic of obesity and diabetes.
About half the adult population has at least one lipid abnormality and about 6% have a triad of lipid abnormalities consisting of an elevated LDL, reduced HDL and elevated triglycerides.
The lipid triad is a strong independent risk factor for cardiovascular disease
Lipids are transported in a protein capsule, lipoprotein, which determines its density.
The lipoprotein density and type of apolipoproteins it contains determines the metabolism of the fat particle.
Divided in primary and secondary subtypes.
Primary hyperlipidemia is usually due to genetic causes, while secondary hyperlipidemia arises due to other underlying causes such as diabetes.
May be an idiopathic process in some cases.
Lipid and lipoprotein abnormalities are modifiable risk factor for cardiovascular disease.
Some forms may predispose to acute pancreatitis.
Can also be classified according to which types of lipids are elevated: hypercholesterolemia, hypertriglyceridemia or both in combined hyperlipidemia.
Primarily lassified according to the Fredrickson classification which is based on the pattern of lipoproteins on electrophoresis or ultracentrifugation.
Type I hyperproteinemia or Familial hyperchylomicronemia is associated with decreased lipoprotein lipase (LPL)
Type I hyperproteinemia associated with increased chylomicrons, abdominal pain from pancreatitis, lipemia retinalis, eruptive skin xanthomas, and hepatosplenomegaly.
Type II Familial hypercholesterolemia associated with LDL receptor deficiency, xanthelasma, arcus senilis, tendon xanthomas.
Type III Familial dysbetalipoproteinemia with a defect in Apo E 2 synthesis, associated with Xanthomas & Palmar Xanthomas
Type IV Familial hypertriglyceridemia associated with increased VLDL production and decreased elimination.
VLDL can cause pancreatitis at high triglyceride levels.
Type I hyperlipoproteinemia has a number of subtypes: Lipoprotein lipase deficiency -Type Ia- due to a deficiency of lipoprotein lipase. Altered apolipoprotein C2, resulting in elevated chylomicrons. Familial apoprotein CII deficiency -Type Ib- a condition caused by a lack of lipoprotein lipase activator. Chylomicronemia due to circulating inhibitor of lipoprotein lipase, Type Ic.
Type I hyperlipoproteinemia presents in childhood with eruptive xanthomata and abdominal colic.
Type I hyperlipoproteinemia complications include retinal vein occlusion, acute pancreatitis, steatosis and lipemia retinalis.
Hyperlipoproteinemia type II is the most common form.
Hyperlipoproteinemia type II is classified into type IIa and type IIb, depending mainly on whether there is elevation in the triglyceride level in addition to LDL cholesterol.
Type IIa Familial hypercholesterolemia may be sporadic, polygenic, or familial as a result of a mutation either in the LDL receptor gene on chromosome 19.
Type IIa Familial hypercholesterolemia characterized by tendon xanthoma, xanthelasma and premature cardiovascular disease.
Type IIa Familial hypercholesterolemia incidence is about 1 in 500 for heterozygotes, and 1 in 1,000,000 for homozygotes.
Type IIb Familial hypercholesterolemia is associated with high VLDL levels due to overproduction of substrates, including triglycerides, acetyl CoA, and an increase in B-100 synthesis and decreased clearance of LDL.
Type IIb Familial hypercholesterolemia has a prevalence in the population of 10%.
Hyperlipoproteinemia type III is due to high chylomicrons and intermediate density lipoprotein (IDL).
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), and its prevalence has been estimated to be approximately 1 in 10,000.
Hyperlipoproteinemia type IV
Familial hypertriglyceridemia is an autosomal dominant condition occurring in approximately 1% of the population.
Hyperlipoproteinemia type V
Hyperlipoproteinemia type V is very similar to type I, but with high VLDL in addition to chylomicrons, glucose intolerance and hyperuricemia
Non-classified forms are extremely rare and include Hyperalphalipoproteinemia, and Polygenic hypercholesterolemia.
Acquired hyperlipidemias mimic primary forms of hyperlipidemia and can premature atherosclerosis or, when associated with marked hypertriglyceridemia, may lead to pancreatitis and other complications of the chylomicronemia syndrome.
The most common causes of acquired hyperlipidemia are: diabetes mellitus, diuretics, beta blockers, and estrogens.
Conditons associated with hyperlipidemia include Hypothyroidism, renal failure, nephrotic syndrome. alcohol, some rare endocrine and metabolic disorders.
In acquired hyperlipidemia treatment of the underlying condition, or discontinuation of the offending drugs usually leads to an improvement in the hyperlipidemia, however lipid-lowering therapy may be required in certain circumstances.
For treatment of type II, dietary modification is the initial approach but many patients require treatment with statins 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.
Agents commonly added to statins are ezetimibe, niacin and bile acid sequestrants.
Dietary supplementation with fish oil is also used to reduce elevated triglycerides, with the greatest effect occurring in patients with the greatest severity.
May be seen in familial or secondary dyslipidemia, hypothyroidism, nephrotic syndrome or with certain medications such as thiazides, atypical antipsychotic agents and oral contraceptive use.