Type 3 Hyperlipidaemia
Also known as dysbetalipoproteinaemia or remnant hyperlipidaemia. It is an inherited lipid disorder with an incidence of about 1 in 5000. It is passed from parent to child, but only 1 in 4 children are affected.
Typically both cholesterol and triglyceride (ordinary fat) levels are high. Some people will show characteristic yellow deposits (xanthomas) in the creases of the hand (palmar creases) and at the elbows and knees. These, if present, normally disappear on treatment.
People with type 3 hyperlipidaemia should be seen in a lipid clinic. If untreated the condition can result in early onset cardiovascular disease. However it does respond very well to medication, and is usually treated with fibrates and statins.
How is it treated?
Most people require a combination of statins and fibrates and sometimes other treatments are added. The aim is to achieve a total cholesterol level below 4 mmol/l (millimols per litre of blood) and a non HDL cholesterol below 2.8mmol/.
A healthy diet and regular exercise are particularly important in achieving good control. People with this condition need careful follow up to adjust their treatment as they get older.
How is type 3 hyperlipidaemia inherited?
The condition is linked to alterations in the APOE gene. However inheriting only one copy of an altered APOE gene does not appear to cause the condition. Inheritance of 2 copies of the APOE2 variant can cause clinical symptoms. Signs of the condition usually appear in adulthood and frequently after the menopause in women.
How is it diagnosed?
Type 3 hyperlipidaemia is not easy to diagnose. A fasting blood test will show raised levels of cholesterol and triglyceride, usually around 10mmol/l. The typical pattern of lipoproteins (particles that carry fat in the blood) is different to other inherited lipid conditions with increased levels of remnant particles, which appear after meals and which contain both cholesterol and triglyceride. Low density lipoprotein (LDL) is often normal or low. This characteristic pattern of blood fats is key to making a diagnosis. Genetic testing cannot be used to diagnose type 3 hyperlipidaemia however other specialised tests are often required to make a final diagnosis.