What is familial hypercholesterolaemia?
Familial hypercholesterolaemia is a term applied to an inherited condition in which low-density (LDL) cholesterol (often referred to as bad cholesterol) is at a higher than normal level in the blood. See separate leaflet called ‘Cholesterol’ for more information about cholesterol and the different types of cholesterol.
What causes familial hypercholesterolaemia?
Familial hypercholesterolaemia is caused by a defect in a gene which controls the way cholesterol is handled in the body. As a result of the defect, LDL cholesterol is not broken down properly and builds up in the bloodstream. In most cases the defective gene is inherited from one parent (heterozygous inheritance). If you inherit it from both parents (homozygous inheritance), the condition is more severe. Heterozygous familial hypercholesterolaemia affects about 1 in 500 people. The homozygous condition is rare.
What are the features of familial hypercholesterolaemia
The most important feature is the development of heart disease at a young age. This is caused by plaques of atheroma developing within the walls of the coronary (heart) arteries (see below). This can lead to a heart attack (myocardial infarction) as a young adult. You might also notice:
- Xanthomas – fatty cholesterol-rich deposits in the skin, usually found around the elbows, knees, buttocks and tendons.
- Xanthelasmas – fatty deposits in the eyelids.
- Arcus senilis – a white ring around the cornea (the coloured part of the eye).
What are atheroma and cardiovascular diseases?
Patches of atheroma are like small fatty lumps that develop within the inside lining of arteries (blood vessels). Atheroma is also known as atherosclerosis and hardening of the arteries. Patches of atheroma are often called plaques of atheroma. A main risk factor for developing atheroma is a high blood cholesterol level.
Over months or years patches of atheroma can become larger and thicker. So, in time, a patch of atheroma can make an artery narrower. This can reduce the blood flow through the artery. For example, narrowing of the coronary (heart) arteries with atheroma is the cause of angina.
Sometimes a blood clot (thrombosis) forms over a patch of atheroma and completely blocks the blood flow. Depending on the artery affected, this can cause a heart attack, a stroke, or other serious problems.
Cardiovascular diseases are diseases of the heart muscle or blood vessels. When doctors say cardiovascular disease they usually mean diseases of the heart or blood vessels that are caused by atheroma.
In summary, cardiovascular diseases that can be caused by atheroma include: angina, heart attack, stroke, transient ischaemic attack (TIA, or mini-stroke), and peripheral vascular disease. In the UK, cardiovascular diseases are a major cause of poor health, and the most common cause of death.
How is familial hypercholesterolaemia diagnosed?
You may be diagnosed by chance if you go for a health screening check or you may notice fatty deposits on the skin or around the eyes.
Another member of your family may be diagnosed with familial hypercholesterolaemia or have a heart attack before the age of 50, and you may be advised to have a check yourself.
You will be advised to have a blood test to check your cholesterol. Familial hypercholesterolaemia is suspected in adults if the total cholesterol is 7.5 mmol/L or greater, or the LDL cholesterol is 4.9 mmol/L or greater. In children (between the ages of 10 and 15) the levels are 6.7 mmol/L and 4.0 mmol/L respectively.
What are the aims of treatment?
You are unlikely to have any symptoms from the heterozygous (less severe) form of familial hypercholesterolaemia as a child or young adult. However, you should be treated to stop symptoms and complications from developing when you are older – the most important of which is heart disease that may develop at an earlier age than usual.
What are the treatment options for familial hypercholesterolaemia?
Being a genetic disorder, familial hypercholesterolaemia is not caused by an unhealthy lifestyle. However, keeping yourself in the best physical condition will help to prevent future problems.
Things you can do to help yourself include:
- Eating healthily – you will almost certainly be referred to a dietician to help you with this, even if you are not overweight.
- Getting a reasonable amount of exercise.
- Avoiding smoking.
- Maintaining a normal weight.
You will be offered medication to help bring your cholesterol level down. The usual medicine to start with is a statin. The most common statin used is called simvastatin. If the level does not come down, another medicine called ezetimibe is sometimes added.
Affected children usually start statin medication in late childhood or early adolescence. Some children may need apheresis (a treatment which filters LDL cholesterol out of the blood). This is offered to those who have the greatest risk of developing problems. In particular, those with the rare homozygous form of familial hypercholesterolaemia.
Your GP may want to discuss referring you to a specialist. A specialist can advise about your treatment and arrange the testing of close members of your family.
What is the outlook (prognosis)?
The outlook for people with heterozygous familial hypercholesterolaemia is usually good if you maintain a healthy lifestyle, have regular checks and take your medication without fail. The most significant complication is heart disease or another cardiovascular disease that may develop at a younger age than usual. The outlook for those with the more severe (homozygous) form of the condition is less good.
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