Familial hypercholesterolaemia (FH)

Reviewed by Dr Neal Uren, consultant cardiologist and Dr Dan Rutherford, GP

What is familial hypercholesterolaemia?

Raised cholesterol levels in the blood - hypercholesterolaemia - are generally caused by a poor diet and lifestyle in combination with the way an individual produces cholesterol in their liver.

However, in some individuals (1 in 500 of the population), the high cholesterol level in the blood is caused by a specific genetic defect. People with inherited or familial hypercholesterolaemia (FH) are lacking in the low-density lipoprotein (LDL) receptors that remove cholesterol from the bloodstream.

The raised cholesterol level in the blood is present from birth and it leads to an early development of atherosclerosis and vascular diseases.

The disease is transmitted from generation to generation in such a way that siblings and children of a person with FH have a 50 per cent risk of getting FH. The disease does not skip generations which means that children and grandchildren of family members who do not have a defective gene are therefore not at risk from FH.

The ailment is mostly treated with medicines and special diets. Treatment with genetic manipulation is still at the experimental stage.

What causes FH?

On all the cells of the body (and mainly in the liver) there is a receptor that allows the fat called LDL (low-density lipoprotein) cholesterol to be cleared from the bloodstream.

People with FH have a defect in the gene of this LDL-cholesterol receptor which causes an accumulation of LDL-cholesterol in the blood and ultimately in the arterial vessel wall. LDL-cholesterol is the most atherogenic type of different cholesterol particles in the circulation.

The genetic basis for the LDL-cholesterol receptor has been well researched and today we know of more than 300 different gene defects that lead to FH.

What are the symptoms of FH?

People with FH cannot feel that they have a raised cholesterol level, but they might have symptoms of cardiovascular disease, which develops as a result of the narrowing of the arteries. The symptoms can include:

pressing, crushing pain behind the breastbone, possibly radiating to the arm or to the neck, associated with physical exertion or cold (angina pectoris).

if the symptoms become more severe and sustained it may be a sign of an acute coronary thrombosis .

The development of atherosclerosis begins in childhood and can be compared to calcium deposits in a water pipe. Gradually, the opening gets smaller and smaller, the inner surface becomes more irregular, the blood can no longer flow freely, leading to symptoms.

When the blood supply to the tissue stops, the tissue dies. This means that if a blood clot is situated in one of the vessels of the heart (the coronary arteries), the area of the heart muscle supplied by that vessel is injured irreversibly. Scar tissue forms and the heart is left weakened.

Why do you get raised cholesterol?

Both hereditary and environmental factors affect the cholesterol level. Today we know of several hereditary disorders that cause significantly raised LDL-cholesterol.

The cholesterol level in northern European countries is higher than in southern Europe and much higher than in Asia. We know that diet is a major factor but there is no doubt that genes also play a part.

Raised blood cholesterol can also be a feature of the following diseases:

hypothyroidism (underactive thyroid gland)

kidney diseases

diabetes

alcohol abuse.

What can I do myself?

In the case of FH, raised cholesterol is the most important risk factor in developing arterial disease. However, other factors also have an influence on this process. It is therefore important to establish a sensible lifestyle in childhood and continue this into adulthood.

A diet low in cholesterol and fat and rich in wholemeal bread, fruits, vegetables, small amounts of lean meat, fish and olive oil is generally recommended.

Moderate consumption of red wine reduces the damaging effects of LDL-cholesterol (bad cholesterol), and increases high-density lipoprotein (HDL) cholesterol (good cholesterol). However this is not appropriate for children or teenagers.

It is very important to stop smoking. In patients with severe hypercholesterolaemia, smoking significantly increases the risk of a serious heart condition.

An active lifestyle and physical exercise strengthen the heart and reduce the risk of cardiovascular disease.

Signs of FH

Cholesterol deposits over tendons (for example, the Achilles tendon) or in the skin around the eyes indicate FH. These look like whitish streaks on the skin.

Family history of raised cholesterol and premature coronary artery disease is another indicator of FH.

How does the doctor make the diagnosis?

After a 10-hour fast (in which only water is consumed), a blood sample is taken in order to determine the level of cholesterol, LDL- cholesterol, HDL-cholesterol and triglyceride in the blood. The results suggest FH if the LDL-cholesterol levels are raised to a very high level.

If both LDL-cholesterol and triglycerides are raised in this situation, the patient may have familial combined hyperlipidaemia, which is another genetic condition.

The test levels are adjusted to take into account age, weight, diabetes, kidney diseases and decreased metabolism. It should be noted that the cholesterol count rises during pregnancy, and drops significantly for at least three months after a heart attack. This could lead to a misdiagnosis in the case of a mild (polygenic) hypercholesterolaemia but not with respect to FH.

By examining the patient's heart and the large blood vessels, feeling the pulse, taking blood pressure and doing an exercise stress test, the doctor can make a rough estimate of the extent of cardiovascular disease.

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