Cholesterol

Cholesterol is a waxy, fat-like substance made in the liver, and found in the blood and in all cells of the body. It is important for good health and is needed for making cell walls, tissues, hormones, vitamin D, and bile acid. Too much cholesterol in the blood may build up in blood vessel walls, block blood flow to tissues and organs, and increase the risk of developing heart disease and stroke.

Does High Cholesterol Run In Your Family?

In some families, high cholesterol is caused by Familial Hypercholesterolemia, or FH.

What Is Familial Hypercholesterolemia?

FH is a genetic disorder that leads to aggressive and premature cardiovascular disease. This includes problems like heart attacks, strokes, and even narrowing of our heart valves. For individuals with FH, although diet and lifestyle choices are important, they are not related to the cause of high LDL. In FH patients, genetic mutations make the liver inadequent in metabolizing or removing excess LDL. The result is very high LDL levels which can lead to premature cardiovascular disease, CVD or coronary artery disease, CAD.

FH Facts

  • About 1 in 250 people worldwide have FH.
  • An estimated 1.3 million people in the U.S. live with FH.
  • Over 90% of people with FH have not been properly diagnosed.
  • FH runs in families. If one parent has FH, each child has a 50% chance of having FH.
  • If left untreated, men have a 50% rise of having a heart attack by age 50. Untreated women have a 30% risk by age 60.
  • FH is even more common in certain populations such as French Canadians, Ashkenazi Jews, Lebanese, and South African Afrikaners. In these populations FH may be found as frequently as 1 in every 67 people.

How Do I Know I Have FH?

Familial Hypercholesterolemia is usually an “invisible” disease, meaning people do not often show visible signs of having it.

There are two main indicators of a Familial Hypercholesterolemia(FH) diagnosis:

1) High levels of LDL-cholesterol*, which do not go down with diet.

*FH is suspected when LDL-cholesterol is above 190 mg/dL in adults and above 160 mg/dL in children without cholesterol-lowering treatment.

2) Family history of early heart disease and/or heart attacks.

Sometimes There Are Visible Signs Of Familial Hypercholesterolemia (Especially When The LDL-Cholesterol Is Very High).

These include:

  • Bumps or lumps around the knuckles, elbows, and knees, called “xanthomas”. These are formed when excess cholesterol deposits on tendons or under the skin. They may be noticed by a dermatologist.
  • Swollen or painful Achilles tendons (“tendon xanthomas”). Excess cholesterol may deposit in the tendons, which makes
    them enlarged and may cause pain when wearing shoes.
  • Yellowish areas around the eyes (“xanthelasmas”) or a white arc near the colored part of the eye (“corneal arcus”), which may be noticed by an ophthalmologist.

How Can Genetic Testing For FH Help?

An oral buccal or cheek swab can help you find out whether you have a mutation that causes FH. If the test detects a mutation that causes FH, you have treatment options which could lower your risk for CAD. Getting tested can also provide important information to your family.

Who Should Be Tested?

Talk with your provider about testing if any of the below are true about you or someone in your family:

  • Has untreated low-density lipoprotien (LDL-C) levels
  • ≥190 mg/dL (≥160 mg/dL with treatment) or levels
  • ≥160 mg/dL in an untreated child
  • Has early CAD or other cardiovascular disease
  • Has xanthomas or corneal arcus
  • Has a mutation that causes FH

What Will The Results Tell Me?

These tests can tell if you have a mutation(s) that is causing your high cholesterol or the high cholesterol that runs in your family. If you find a genetic cause for your high cholesterol, it can help your doctor treat you more appropriately and lower your risk for CAD.

If Testing Finds A Mutation That Causes FH, What Does This Mean For My Family Members?

Because we share some of our genes with our relatives, if someone in your family has a mutation that causes FH, other family members may have the same mutation. This would mean an increased risk for high cholesterol leading to CAD.
The most common form of FH is called heterozygous FH (HeFH). This means you inherited a mutation that causes FH from either your father or your mother. If you have HeFH, your brothers, your sisters, and your children each have a 50% chance of having the same mutation. Other relatives are also at risk. It is therefore important to share your test results with your family.

Relative Relative’s Chance of having same mutation 
Identical Twin 100%
Parent, sibling, child, fraternal twin 50%
Grandparent, uncle, aunt, niece, nephew 25%
First Cousin 12.5%

 

There is a less common form of FH called homozygous FH (HoFH). This means that you inherited a mutation that causes FH from both your mother and your father. If you have HoFH, your relatives may be at risk for either HeFH or HoFH. HoFH is very rare and occurs in about 1 in 160,000 to one million people worldwide. They should discuss this further with their doctors.

What Do My Test Results Mean?

Your healthcare provider or genetic counselor will explain what your test results mean. There are three possible results:

Negative
The test did not find a mutation that causes FH.

  • If your family has a known FH-related mutation and your cholesterol is normal, then you are not at risk for FH.
  • If your family does not have a known FH-related mutation, then your risk for high cholesterol may still be increased. In some
    cases, testing other genes or other relatives may be recommended.
  • If you have a clinical diagnosis of FH, your negative genetic test does not change your diagnosis. You may have a form of FH
    caused by rare genetic changes, some of which may not yet be known.

Positive
The test found a mutation that causes FH. The mutation is referred to as a pathogenic or likely pathogenic variant on your report.

  • Individuals with FH have high levels of LDL cholesterol (LDL-C). This may increase the risk for early CAD and heart attack.
  • Individuals with FH may have either HeFH or HoFH. You and your healthcare provider will talk about ways to lower your risk, such as medications and lifestyle changes.

Variant Of Unknown Clinical Significance

  • It is not uncommon to find changes in genes with an unknown effect. We call these “variants of unknown clinical significance (VUS).” Over time, we may learn more. Check with your healthcare provider each year for updates about VUS.

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