Analysis Of Familial Hypercholesterolemia Biology Essay

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Familial Hypercholesterolemia it is a genetic disorder caused by defect in the chromosome 19. Fh is an autosomal dominant disease and this is inherited disease. So if you get one abnormal gene from one of the parent you get the disease and this is heterozygous familial hypercholesterolemia and occurs 1 per 500 people. In some cases a child may inherit the gene from both parents. These individuals who inherit both genes are considered "homozygous." Homozygous familial hypercholesterolemia is much more severe.

  Familial Hypercholesterolemia is malfunctioning of the low density lipoprotein(ldl) . This ldl gene is located on the short arm of chromosome 19p13,and protein is composed of 860 amino acids. Normally LDL receptor is the primary determinant of hepatic LDL uptake, which normally processes approximately 70% of circulating LDL. "There is a mutation in the genetic encoding for the LDL receptors  that are located on the surface of the liver cells. The main function of these receptors is to pick up the circulating level of plasma LDL to be processed in the liver and to manage the cholesterol level. As the result of the lack of activity, the LDL particles are not recycled and are circulating in the bloodstream, a condition of hypercholesterolemia. This defect makes the body unable to remove the low density lipoprotein ( bad cholesterol) from the blood. This results in high levels of LDL in the blood."(1)

If the cholesterol level increases above 600mg/dl there is a great increase of heart disease.

 High levels of LDL cholesterol in your body make you more likely to have narrowing of the arteries from atherosclerosis  at an early age.Atherosclerosis is a condition in where fatty material collects along the walls of arteries. This fatty material thickens, hardens forms calcium deposits and may eventually block the arteries. Those who has familial hypercholesterolemia are more likely to have a family history of high cholesterol and heart disease at a relatively younger age than normal. Eventually, these plaques can make the artery narrow and less flexible, making it harder for blood to flow. If the coronary arteries become narrow blood flow to the heart can slow down or stop. This can cause chest pain shortness of breath, heart attack and even some other symptoms.


Homozygous FH

Severe and widespread atherosclerosis affects all major arterial beds, including the carotid, coronary, femoral, and iliac.

Children are at risk for early coronary events, and sudden death or acute myocardial infarction may occur in patients as young as 1-2 years.

Valve abnormalities are common, particularly aortic stenosis.

Accumulation of cholesterol in nonvascular tissue is of less clinical significance Tuberous xanthomas(kind of harmless growth of tissue) are present early in childhood and sometimes at birth. Recognition of the cutaneous manifestations of FH permits early diagnosis and treatment to prevent the otherwise severe cardiovascular complications.

These patients may have cutaneous xanthomas at birth or by early childhood.

Many types of xanthomas are usually obvious in the first decade of life, and some are (a) planar xanthomas ( mainly on elbows and hands, buttocks, or knees)and con be used for diagnosis from other cutaneous xanthomas because of their yellow-to-orange coloration; (b) Tuberous xanthomas (seen in hands and elbows); and (c) tendon xanthomas (mainly seen on extensor tendons of hands or Achilles tendon) will occur somewhat later.

Children may have corneal arcus, which is sometimes circumferential. While occasionally present in older adults with normal cholesterol levels, corneal arcus is highly unusual in children.

The murmur for the aortic stenosis may be heard.

Hetrozygous Familial Hypercholesterolemia:-

Premature CAD is the most serious and preventable manifestation. If this is not treated men are likely to develop symptoms by the fourth decade of life. The onset of symptoms in women lags behind men by approximately 10-15 years.

Cholesterol deposition in nonvascular tissue is common, although heterozygous children do not usually have physical manifestations; adults do not invariably develop them. Corneal arcus (deposition of cholesterol in the corneal stroma).This is the most frequent finding, particularly in patients older than 30 years, but this finding is also common in older patients and African Americans without hypercholesterolemia. Similarly, xanthelasmas can occur in older individuals with normal cholesterol levels.

Xanthomas, most commonly of the Achilles tendon and extensor tendons of the hands, are rare in children and common in untreated adults. Tendon xanthomas may occur with other conditions such as familial defective apoB-100 and type III hyperlipoproteinemia. These deposits can cause Achilles tendonitis and articular symptoms, particularly of the hands, wrists, knees, and ankles.

Diagnosis:The diagnosis for both homozygous and heterozygous FH is based primarily on the elevation in triglyceride level

LDL receptor analysis can be used to identify the specific LDL receptor defect. However, this analysis can only be performed at certain research laboratories and is expensive. LDL receptor & apoB-100 studies may help to distinguish FH.

In patients with heterozygous Familial Hypercholesterolemia. LDL levels are commonly higher than 250 mg/dL and usually increase with age.

Treatment:FH is a condition In which body is unable to metabolize dietary fats and results in elevated blood cholesterol . For gene therapy a section of the liver is removed and mouse virus carrying a human gene for cell surface cholesterol receptor is used to infect the liver cells .The treated cells are then injected into the patient using a vein that supplies the liver.The injected cells are carried through vein and these cells start to metabolize the cholesterol level.

Treatment for homozygous FH:-

High doses of HMG coA reductase inhibitors given with bile acid seqrestrants and niacin can be effective.

Estrogen replacement therapy in postmenopausal women is also effective not for old people.

Liver transplantation may be also effective.

Treatment for heterozygous FH:-

Aerobic and toning exercises improve blood lipid levels if performed for longer than 30 minutes 4 or more days per week.

With 50% functional LDL receptors, heterozygous FH patients have an excellent response to the usual cholesterol-lowering drugs

Diets should be rich in whole grains, whole fruit, and legumes and other vegetables. These foods are high in soluble fiber, which has a small 5% cholesterol-lowering effect; they are also high in antioxidants and flavonoids, which may be cardioprotective .

Suplementation of niacin also regulates the cholesterol level