Summary

• Familial hypercholesteraemia (FH) is an inherited disorder that is caused by changes, also called variants in the genes that help control how your body removes cholesterol from your blood.
• If you have FH, you have higher-than-normal LDL cholesterol from birth, which increases your risk of having heart disease or a heart attack at an earlier age.
• A genetic test for FH is available but it is only ordered if you have had test results that show you have high cholesterol and you have other risk factors.
• Diagnosing FH and treating it with cholesterol-lowering medication can reduce your risk of heart disease.

What is cholesterol and why does it matter?

Cholesterol is a type of waxy fat, that performs a range of important functions in the body. We cannot live without cholesterol. It’s found in every cell in our body and is involved in a whole host of vital processes. All the cholesterol you need is made in your liver and the rest comes from foods you eat, like meat and dairy. High amounts of cholesterol in your blood can lead to health problems.

Cholesterol is carried around the bloodstream in lipoproteins.  All cholesterol is the same – it’s the lipoproteins that carry it that are different, and this is what matters.

Lipoproteins are round particles of fat and proteins that travel in your bloodstream to cells throughout your body. Cholesterol and triglycerides are two types of lipids found in lipoproteins.

Different types of cholesterol

There are several types of lipoproteins, and the main ones are High-Density Lipoprotein (HDL) sometimes called ‘good’ cholesterol and Low-Density Lipoprotein (LDL) or ‘bad’ cholesterol. When cholesterol is carried by HDL it is called HDL cholesterol and when it is carried by LDL it is called LDL cholesterol.

• LDL (low-density lipoprotein) deposits cholesterol into blood vessel walls causing plaques to form. By lowering LDL it’s possible to reduce the cholesterol inside plaques.
• HDL (high-density lipoprotein) helps remove cholesterol from artery walls. Having a normal HDL level is important.

How plaques form

LDL cholesterol sticks together with other fats, cells, calcium and debris floating around in the bloodstream and forms plaques in the walls of arteries. The build-up of plaque narrows the space within the artery.

Over time, a tough, fibrous cap or scar forms over the soft sticky plaque and if this breaks open – say, if your blood pressure spikes – a blood clot forms over the rupture. This blocks the blood flow which can lead to a heart attack or stroke. There are different types of plaques. Some grow slowly and may never cause problems, even when the plaque is large enough to restrict blood flow through the artery.

By reducing cholesterol from the plaques, you can reduce your risk of heart attack or stroke. It’s possible to do this by lowering the amount of LDL travelling around in your blood.

What is FH?

FH is an inherited disorder, which causes very high LDL cholesterol from birth and will continue to do so throughout life unless it is diagnosed and treated. If you have FH, you can develop arterial disease in young adulthood.

Normally, the body’s cells, particularly the liver cells, clear LDL cholesterol particles from the blood through receptors. These are on the surface of the cell. 

For people with the most common form of FH, half of these LDL receptors do not work properly. This means the LDL cholesterol cannot be removed efficiently from the blood.

The production of LDL receptors is controlled by genes. Normally, a person has two working copies of the genes controlling the receptors. One copy of the gene is inherited from their mother and one from their father.

If you have FH, you have inherited one faulty copy of the gene from one parent and one working copy of the gene from your other parent. This means only half of your LDL receptors are not working properly, and they can’t remove LDL cholesterol from the blood.

Inheriting only one copy of a faulty gene in each cell is sufficient to cause the disorder. With fewer cholesterol receptors, LDL cholesterol is not absorbed into cells as well as it should be and stays circulating in the blood. Rarely, someone with FH has an alteration in both copies of the gene.

Testing for FH

FH is caused by a change, also called a variant, in the LDL receptor gene (LDL-R) or occasionally in other genes (APOB or PCSK9).  

A genetic test for FH is only ordered if you have already had test results that show you have high cholesterol and other risk factors.

If you have cholesterol tests that show you have a total cholesterol greater than 7.5 mmol/L or LDL cholesterol greater than 5.0 mmol/L, especially if there is a history of premature coronary heart disease in your family your medical team will perform a Dutch Lipid Clinic Network Score.  

This is a calculation based on your family history, untreated LDL cholesterol levels and physical signs.

Having a genetic test

There are two types of genetic testing:

• A test looking at your DNA to search for any variant in the FH-causing genes.
• A test looking at your DNA for only a specific variant that has previously been identified in your family.

Medicare
FH genetic testing is covered by Medicare only when it is requested by a specialist doctor if they suspect your high LDL cholesterol is due to FH.

It is also covered when ordered by a GP or specialist doctor to test first-degree relatives (parents, children, or siblings) or second-degree relatives (grandparents, grandchildren, uncles and aunties) if you have been diagnosed with FH.

Having the test

Sample

Blood.

Any preparation?

None.

Your results

Family testing

If you have FH confirmed by genetic testing and you are the first person in your family to be diagnosed, you are termed an ‘index case’. Each of your close family members – parents, siblings, and children – has a 50 per cent chance of also having the gene variant causing FH and they should be tested. The diagnosis of FH in children should ideally occur before they are 10.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record.

You and your healthcare provider can now access your results whenever and wherever needed. Get further trustworthy health information and advice from healthdirect.