Inherited conditions in which the blood contains abnormally high levels of cholesterol and/ or triglycerides
Many people have an elevated level of cholesterol in their blood (see Hypercholesterolaemia). In some of these people, levels of cholesterol and of lipids called triglycerides are high due to genetic disorders called hyperlipidaemias. The disorders create high levels of lipoproteins (lipid–protein particles), and may produce symptoms earlier in adulthood than other hypercholesterolaemias. High levels of lipids (especially cholesterol) increase the risk of complications of atherosclerosis, such as coronary artery disease.
There are several forms of inherited hyperlipidaemia. The most common affects about 1 in 500 people of European descent, who inherit one copy of an abnormal gene and have a cholesterol level two or three times higher than normal. There is a one in a million risk that people will inherit the abnormal gene from both parents. If two copies are inherited, the cholesterol level is six to eight times higher than normal. Affected people have a very high probability of a heart attack (see Myocardial infarction), even in childhood.
Extremely high cholesterol levels associated with inherited hyperlipidaemias may cause the following symptoms, which develop gradually over years:
Yellow swellings under the skin (xanthomas) on the back of the hands.
Swellings on the tendons around the ankle and wrist joints.
Yellow swellings on the skin of the eyelids (xanthelasmas).
White ring around the iris (the coloured part of the eye).
Raised triglyceride levels do not usually produce any symptoms but do increase the risk of acute pancreatitis.
Men with these disorders can develop symptoms of coronary artery disease, such as chest pain (see Angina), in their 20s or 30s. In women, oestrogen usually gives protection from these problems until after the menopause.
There is no cure for inherited hyperlipidaemias, but symptoms can be treated with a combination of exercise, a diet that is low in cholesterol and saturated fats, and lipid-lowering drugs. The outlook varies, but early lipid-lowering treatment can greatly reduce the risk of a heart attack. Relatives of an affected person should be offered screening for the disorder.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.