Familial hypercholesterolemia is an inherited condition that causes high levels of low density lipoprotein (LDL) cholesterol beginning at birth and heart attacks at an early age.
What is familial hypercholesterolemia?
Familial hypercholesterolemia is an inherited condition that causes high levels of LDL (low density lipoprotein) cholesterol beginning at birth, and heart attacks at an early age. Cholesterol is a fat-like substance that is found in the cells of the body. Cholesterol is also found in some foods. The body needs some cholesterol to work properly and uses cholesterol to make hormones, vitamin D, and substances that help with food digestion. However, if too much cholesterol is present in the blood stream, it builds up in the wall of the arteries and increases the risk of heart disease.
Cholesterol is carried in the blood stream in small packages called lipoproteins. These small packages are made up of fat (lipid) on the inside and proteins on the outside. There are two main kinds of lipoprotein that carry cholesterol throughout the body. These are: low density lipoprotein (LDL) and high density lipoprotein (HDL).
The cholesterol carried by LDL is some times called the "bad cholesterol." People who have familial hypercholesterolemia have high levels of LDL cholesterol because they can not remove the LDL from the blood stream properly. The organ responsible for the removal of the LDL is the liver. High levels of LDL cholesterol in the blood increase the risk for heart attacks and heart disease.
The cholesterol carried by HDL is sometimes called the "good cholesterol." HDL carries cholesterol from other parts of the body to the liver. The liver removes cholesterol from the body. Higher levels of HDL cholesterol lower a person's chance for getting heart disease.
Men who have familial hypercholesterolemia have heart attacks in their 40's to 50's, and 85 percent of men with the disorder have a heart attack by age 60. Women who have familial hypercholesterolemia also have an increased risk for heart attack, but it happens 10 years later than in men (so in their 50's and 60's).
Familial hypercholesterolemia is inherited in families in an autosomal dominant manner. In autosomal dominant inherited conditions, a parent who carries an altered gene that causes the condition has a 1 in 2 (50 percent) chance to pass on that altered gene to each of his or her children.
The altered gene (gene mutation) that causes familial hypercholesterolemia is located on chromosome number 19. It contains the information for a protein called LDL receptor that is responsible to clear up LDL from the blood stream. One in 500 individuals carries one altered gene causing familial hypercholesterolemia. These individuals are called heterozygotes. More rarely, a person inherits the gene mutation from both parents, making them genetically homozygous. Individuals who are homozygous have a much more severe form of hypercholesterolemia, with heart attack and death often occurring before age 30.
What are the symptoms of familial hypercholesterolemia?
The major symptoms and signs of familial hypercholesterolemia are:
- High levels of total cholesterol and LDL cholesterol.
- A strong family history of high levels of total and LDL cholesterol and/or early heart attack.
- Elevated and therapy-resistant levels of LDL in either or both parents.
- Xanthomas (waxy deposits of cholesterol in the skin or tendons).
- Xanthelasmas (cholesterol deposits in the eyelids).
- Corneal arcus (cholesterol deposit around the cornea of the eye).
- If angina (chest pain) is present, it may be sign that heart disease is present.
Individuals who have homozygous familial hypercholesterolemia develop xanthomas beneath the skin over their elbows, knees and buttocks as well as in the tendons at a very early age, sometime in infancy. Heart attacks and death may occur before 30.
How is familial hypercholesterolemia diagnosed?
Diagnosis of familial hypercholesterolemia is based on physical examination and laboratory testing. Physical examination may find xanthomas and xanthelasmas (skin lesions caused by cholesterol rich lipoprotein deposits), and cholesterol deposits in the eye called corneal arcus.
Laboratory testing includes blood testing of cholesterol levels, studies of heart function, and genetic testing. Blood testing of cholesterol levels may show: increased total cholesterol usually above 300 mg/dl (total cholesterol of more than 250 mg/dl in children) and LDL levels usually above 200 mg/dl. Studies of heart function, such as a stress test, may be abnormal. Genetic testing may show an alteration (mutation) in the LDL receptor gene.
What is the treatment for familial hypercholesterolemia?
The overall goal of treatment is to lower the risk for atherosclerotic heart disease by lowering the LDL cholesterol levels in the blood stream. Atherosclerosis is a condition in which fatty material collects along the walls of arteries. This fatty material thickens, hardens, and may eventually block the arteries. Atherosclerosis happens when fat and cholesterol and other substances build up in the arteries and form a hardened material called plaque. The plaque deposits make the arteries less flexible and more difficult for blood to flow leading to heart attack and stroke.
The first step in treatment for an individual who has heterozygous familial hypercholesterolemia is changing the diet to reduce the total amount of fat eaten to 30 percent of the total daily calories. This can be done by limiting the amount of beef, pork, and lamb in the diet; cutting out butter, whole milk and fatty cheeses as well as some oils like coconut and palm oils; and eliminating egg yolks, organ meats and other sources of saturated fat from animals. Dietary counseling is often recommended to help people to make these changes in their eating habits.
Exercise, especially to lose weight, may also help in lowering cholesterol levels.
Drug therapy is usually necessary in combination with diet, weight loss, and exercise, as these interventions may not be able to lower cholesterol levels alone. There are a number of cholesterol-lowering medications that are currently used. The first and more effective choice are drugs called "statins." Other drugs that may be used in combination with or instead of the statins are: bile acid sequestrant resins (for example, cholestyramine), ezetemibe, nicotinic acid (niacin), gemfibrozil, and fenofibrate.
Individuals who have homozygous familial hypercholesterolemia need more aggressive therapies to treat their significantly elevated levels of cholesterol. Often drug therapies are not sufficient to lower LDL cholesterol levels at the desiderated goal and these individuals may require periodical LDL apheresis, a procedure to "clean up" LDL from the blood stream, or highly invasive surgery such as a liver transplant.
Is familial hypercholesterolemia inherited?
Familial hypercholesterolemia is inherited in an autosomal dominant manner. This means that to have this condition, it is sufficient that the altered (mutated) gene is present on only one of the person's two number 19 chromosomes. A person who inherits one copy of the gene mutation causing familial hypercholesterolemia from one of his/her parents is said to have heterozygous familial hypercholesterolemia. This person has a 1 in 2 (50 percent) chance to pass on the mutated gene to each of his/her children.
A person who inherits a mutated copy of the gene causing familial hypercholesterolemia from both parents is said to have homozygous familial hypercholesterolemia. This is a much more severe form of familial hypercholesterolemia than heterozygous familial hypercholesterolemia. Each of this person's children will inherit one copy of the mutated gene and will have heterozygous familial hypercholesterolemia.