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Excess blood cholesterol becomes stuck in the linings of an artery, eventually the artery narrows.
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Cholesterol and diet
What is Familial Hypercholesterolemia?
Treatments for Familial Hypercholesterolemia
Our Familial Hypercholesterolemia Video
Our Familial Hypercholesterolemia Guide
Life with Familial Hypercholesterolemia
NICE Guidelines for FH
NICE Quality Standards for FH
Watch this film to hear GP, Dr Sarah Jarvis, and patients, talk about inherited high cholesterol
Polygenic literally means “many genes”. So polygenic hypercholesterolaemia is a form of high cholesterol caused by the small effects of many genes.
What are genes?
Each of us has between 20,000 and 25,000 different genes. Genes give the instructions to our body about how to build cells, tissues and organs and they also control characteristics such as eye colour, height and blood type.
Familial hypercholesterolaemia (FH)
FH is a condition that results in very high blood cholesterol levels. It is caused by an alteration in a single gene. Because it is caused by a single gene it is called “monogenic” which literally means “one gene”. You can find out more about FH here and how it is inherited here.
How is polygenic hypercholesterolaemia diagnosed?
Doctors often come across people with high levels of cholesterol in the blood. Sometimes their medical information will fit the diagnosis criteria for FH but when the doctor looks for an FH causing gene they cannot find one. The most likely explanation is that these people have a polygenic form of high cholesterol. In other words they have inherited a number of genes that each have a small additive cholesterol raising effect.
Doctors have now identified 12 common “altered” genes that might be involved. Each of these “altered genes” can raise LDL cholesterol a little. If a person has inherited several of these genes their cholesterol levels may be too high. This is because the small effects of each gene can add up to a big effect. Together these genes can increase their LDL cholesterol levels sufficiently to meet the diagnostic criteria that doctors use for FH.
How big a concern is polygenic high cholesterol?
Raised cholesterol is one of the main risk factors for circulatory diseases such as heart disease. It contributes to the risk of having a heart attack, a stroke and developing angina. So having high cholesterol, whatever the reason, is a concern for long term health. When assessing your risk doctors and nurses also take into account other risk factors such as your age and whether you smoke, have diabetes or high blood pressure. Reducing the amount of cholesterol you have in your blood is important. Your doctor will advise you about changing your diet and lifestyle and taking medicines such as statins.
Doctors believe that high cholesterol caused by the small effects of several genes (polygenic) is a serious condition and should be managed. However they also believe that the risk posed by polygenic hypercholesterolaemia is less than that posed by FH.
What are the differences between polygenic high cholesterol and FH?
Familial Hypercholesterolaemia (FH)
|Caused by several altered genes (polygenic)||Caused by inheriting a single altered gene (monogenic)|
|Each altered gene raises LDL cholesterol slightly||The altered gene has a large effect on LDL cholesterol|
|Altered genes can be inherited from both parents||The altered gene is usually only inherited from one parent|
|Each parent may not have enough of the LDL raising genes to cause their cholesterol to be raised||The parent with the altered gene will (mostly likely) also have very high LDL cholesterol too|
|The risk from polygenic high cholesterol is thought to be less than that from FH||The risk from FH is thought to be more than that from polygenic high cholesterol|
Is it possible to have FH and polygenic high cholesterol at the same time?
Yes it is possible. It is thought that at least 1 in 500 people in the UK have FH. Some of these people will also have inherited a number of the altered genes, each of which increases LDL cholesterol levels just slightly. Here is an example:
Judith and William are twins. Their mother was diagnosed with FH when she was 35. So Judith and William were tested when they were still children and both were found to have inherited the same FH causing gene as their mother. However at the age of 9 Janet had an LDL cholesterol level of 12.3 mmol/L and her brother’s LDL cholesterol level at the same age was just 7.6 mmol/L. This meant that both of them met the diagnostic criteria for FH. However Janet also had a strong polygenic background and William did not.
If you are a health professional you can find out more about polygenic hypercholesterolaemia here.