What is familial hypercholesterolaemia? 

Familial hypercholesterolaemia (FH) is an inherited genetic condition that causes significantly elevated levels of low-density lipoprotein (LDL) cholesterol in the blood from birth. Unlike standard high cholesterol, which often develops later in life due to lifestyle factors, FH is caused by a genetic mutation that prevents the liver from clearing cholesterol effectively, leading to a much higher risk of premature heart disease if left untreated. 

What We’ll Discuss in This Article 

• The clinical definition of familial hypercholesterolaemia (FH) and how it differs from lifestyle-related high cholesterol. 

• How the condition is inherited through families and the 50% chance of passing it to children. 

• Recognising the physical signs of FH, such as tendon xanthomas and corneal arcus. 

• The diagnostic criteria used in the UK, including the Simon Broome and Dutch Lipid Clinic Network scores. 

• Management strategies involving high-intensity statins and lifestyle modifications. 

• The importance of cascade testing for identifying at-risk relatives. 

• Understanding the role of the BMI Calculator in monitoring overall cardiovascular health. 

Understanding Familial Hypercholesterolaemia 

Familial hypercholesterolaemia (FH) is a common but underdiagnosed genetic disorder affecting approximately 1 in 250 people in the UK. It is characterised by a lifelong exposure to high levels of LDL cholesterol, which can lead to the early development of atherosclerosis (narrowing of the arteries). Because the cholesterol is high from childhood, the cumulative damage to the circulatory system is greater than in people who develop high cholesterol in middle age. 

The condition is primarily monogenic, meaning it is typically caused by a mutation in a single gene most commonly the LDLR, APOB, or PCSK9 genes. These genes provide instructions for making proteins that clear cholesterol from the bloodstream. When they are faulty, the liver’s ability to remove ‘bad’ cholesterol is compromised.  

Clinical Context 

In the UK, the majority of people with FH remain undiagnosed. The NHS 2019 Long Term Plan, which continues to guide care into 2026, set ambitious targets to identify 25% of the predicted FH population. Identifying an ‘index case’ (the first person in a family to be diagnosed) is vital because it triggers cascade testing for all first-degree relatives. 

Clinical Signs and Physical Symptoms 

One of the unique aspects of FH is that it can sometimes cause visible physical signs due to the extreme buildup of cholesterol in tissues outside the bloodstream. While many people with FH have no symptoms until a cardiac event occurs, a clinician will check for specific markers during a physical examination. 

• Tendon Xanthomas: These are firm, fatty lumps that develop over the knuckles, knees, or the Achilles tendon at the back of the ankle. 

• Xanthelasmas: These appear as small, pale yellow lumps of cholesterol in the skin around the eyelids. 

• Corneal Arcus: A white or grey ring around the iris (the coloured part of the eye). If this appears in an individual under the age of 45, it is a strong indicator of FH. 

Physical Sign	Location	Clinical Significance
Tendon Xanthoma	Knuckles, Achilles tendon	Highly specific to FH; rarely seen in other conditions.
Xanthelasma	Eyelids	Suggests high cholesterol but can occur for other reasons.
Corneal Arcus	Edge of the iris	Strong diagnostic marker if found in those under 45.

Causes and Genetic Inheritance 

FH is caused by a genetic mutation that is passed down through families. It follows an autosomal dominant inheritance pattern, which means an individual only needs to inherit one faulty gene from one parent to have the condition. This form is known as Heterozygous FH. 

In very rare cases, a child may inherit a faulty gene from both parents, resulting in Homozygous FH. This is a much more severe form where cholesterol levels can be extremely high (often above 13 mmol/L for adults), and heart disease can develop in early childhood. 

The 50/50 Rule 

If one parent has Heterozygous FH, there is a 50% chance that each of their children will inherit the condition. This is why the NHS prioritises family screening. As stated in the NICE (National Institute for Health and Care Excellence) updates, ‘A diagnosis of FH is a diagnosis for the whole family, and healthcare providers must facilitate the testing of biological relatives to prevent premature cardiovascular mortality.’ 

Triggers and Lifestyle Factors 

While FH is a genetic condition that cannot be caused or cured by lifestyle alone, certain factors can act as ‘triggers’ that significantly worsen the prognosis. For someone with FH, the baseline risk is already high, so adding lifestyle-related stressors can lead to a cardiac event much sooner. 

• Smoking: This is the single most dangerous trigger for someone with FH. Smoking damages the lining of the arteries, making it much easier for high levels of LDL to form plaques. 

• High Saturated Fat Intake: While the liver’s production of cholesterol is the main issue, a diet high in saturated fats adds even more LDL to a system that already cannot clear it. 

• Sedentary Behaviour: Lack of exercise contributes to lower HDL (good) cholesterol, which is needed to help transport some fats back to the liver. 

• Uncontrolled Blood Pressure: High blood pressure puts additional strain on arteries already narrowed by cholesterol deposits. 

Differentiation: FH vs. Non-Genetic High Cholesterol 

It is essential to differentiate between FH and polygenic (standard) high cholesterol, as the management pathways differ. While standard high cholesterol often responds well to diet and exercise alone, FH almost always requires high-intensity medication from a young age. 

Feature	Familial Hypercholesterolaemia (FH)	Standard High Cholesterol
Primary Cause	Single gene mutation (Monogenic).	Combination of many genes and lifestyle.
Age of Onset	From birth.	Typically middle age onwards.
Cholesterol Levels	Often very high (Total >7.5 mmol/L).	Variable; often borderline high.
Family History	Strong history of early heart disease.	Variable; often linked to shared habits.
Treatment	Lifetime medication is essential.	Lifestyle changes may be sufficient.

Diagnosis and Screening in the UK 

In the UK, the diagnosis of FH is made using the Simon Broome criteria or the Dutch Lipid Clinic Network (DLCN) score. These tools combine cholesterol measurements with family history and physical signs to determine the likelihood of the condition. 

If a patient meets the criteria for ‘possible’ or ‘definite’ FH, they are referred to a specialist lipid clinic for genetic testing. This involves a blood test to identify the specific mutation. Once a mutation is found, the patient’s children, siblings, and parents are invited for cascade testing. NICE guidance suggests that children in affected families should be tested by the age of 10 to ensure that treatment can be discussed before adulthood. 

To Summarise 

Familial hypercholesterolaemia (FH) is a serious but manageable genetic condition that causes high cholesterol from birth, significantly increasing the risk of early heart disease. Unlike standard high cholesterol, it is passed down through families and often requires a combination of genetic testing and high-intensity statins for effective management. Early diagnosis through family screening and maintaining a healthy lifestyle are the most effective ways to protect your heart health. 

If you experience sudden, crushing chest pain, shortness of breath, or sudden weakness on one side of your body, call 999 immediately. 

You may find our free BMI Calculator helpful for monitoring your overall health, as maintaining a healthy weight remains an important part of managing cardiovascular risk factors. 

Authority Snapshot 

Dr. Rebecca Fernandez is a UK-trained physician with an MBBS and experience in general surgery, cardiology, internal medicine, and emergency medicine. She has managed critically ill patients, stabilised acute trauma cases, and provided comprehensive inpatient and outpatient care. This article provides evidence-based information aligned with the 2026 clinical standards from the NHS and NICE regarding the identification and management of familial hypercholesterolaemia.