Often heart disease runs in the family, and sometimes large numbers of family members die at a relatively young age of this condition. Our genes affect how high our LDL cholesterol is because they determine how fast LDL is made and removed from the blood. You are two to five times more likely to have a heart attack if a first degree relative has died of coronary heart disease before the age of 60.
There is a genetic condition called familial hypercholesterolemia (FH). It is an autosomal dominant disorder that produces severe elevations in total and LDL cholesterol. The DNA in our cells is packed into chromosomes, which occur in pairs. Autosomal comes from the word «autosome» which means all chromosomes other than the sex chromosomes. Dominant means that only one parent needs to contain the defective gene to pass it on to their offspring.
Heterozygous familial hypercholesterolemia occurs in approximately 1in 500 people worldwide, and it causes an approximate doubling in LDL cholesterol levels.
Heterozygous means that only one defective gene is present for a condition, so it usually produces a less severe case of the disease. In other words only one parent passed the condition on, rather than both parents. FH is especially common in French Canadians, Lebanese, South Africans and Ashkenazi Jews.
In FH the LDL receptors are either missing or deformed. These receptors are required in order for the liver to take up LDL that has been floating in the bloodstream, process it and remove it from the bloodstream. If the liver can’t take up LDL particles, blood levels quickly rise. Also, if LDL is not able to get into liver cells, it can’t suppress the production of more cholesterol, therefore greater amounts of cholesterol are produced, and blood levels rise. In people with heterozygous FH, only half the normal number of LDL receptors is present. Commonly, levels of LDL cholesterol will be between 5.1 and 10.3 mmol/L. In normal healthy people LDL cholesterol should be no higher than 3.5 mmol/L. People with heterozygous FH typically develop premature coronary artery disease; men typically in their forties, and women 10 to 15 years later.
Homozygous familial hypercholesterolemia is a much more severe case of the disease, as both genes are defective. It affects approximately one in one million people. In people with this condition sudden death due to a heart attack occurs as early as age 1 to 2 years.
High blood levels of LDL cholesterol in people with FH means that various cells in the body that do not require LDL receptors, take up and absorb cholesterol. This includes monocytes and macrophages, which can turn into foam cells and lead to the production of fatty plaques in the arteries.
People with familial hypercholesterolemia often display telltale signs on their bodies called xanthomas. The word xanthoma is derived from the Greek word xanthos, which means yellow. Most xanthomas have a yellowish appearance, but this isn’t always the case. They are basically deposits of fat, connective tissue and blood vessels in and under the skin which grow on various sites of the body. People with familial hypercholesterolemia typically develop xanthomas on their Achilles tendons and tendons on the hands. Sometimes a xanthoma develops on the inner side of the eyelid; this is called a xanthelasma. An iridologist looking in the iris of a person with FH will usually see an arcus senilis, this is a cloudy ring on the outer border of the iris. There are several other genetic conditions besides FH which produce severely elevated levels of LDL cholesterol.
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