Homozygous & Heterozygous Familial Hypercholesterolemia | FH
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What is FH?

FH is short for Familial Hypercholesterolemia. It is an inherited disorder that leads to aggressive and premature cardiovascular disease. For individuals with FH, diet and lifestyle are not the cause, although they can still make a difference.

The vast majority of the cholesterol circulating in a person’s body is produced by the liver. Cholesterol is a necessary component in the structure and function of human cells. Individuals with FH are unable to recycle this natural supply of cholesterol that their bodies are constantly producing. Therefore, the cholesterol levels of an individual with FH are exceedingly high. Over time the elevated blood cholesterol can lead to blockages in the arteries of the heart and/or brain.

There are two forms of FH. If you have inherited this genetic mutation from one parent, then you will have Heterozygous FH (HeFH). HeFH occurs in 1 in 300 to 500 people worldwide. If you inherit FH from both parents, it is much more severe in its consequences. This form of FH is called Homozygous FH (HoFH). It is very rare, occurring in about 1 in a million people worldwide.

Cholesterol is a fatty substance, or lipid, in your bloodstream. It is measured in milligrams per deciliter (mg/dL). There is “good cholesterol,” known as high density lipoprotein cholesterol (HDL-C), and “bad cholesterol,” known as low density lipoprotein cholesterol (LDL-C).

Adults with FH may have LDL-C levels that range from 190mg/dL to 400mg/dL or higher. Children with FH have LDL-C levels above 160mg/dL.

  • High HDL-C levels are desirable and protect against coronary heart disease (CHD).
  • High LDL-C levels are undesirable and contribute to CHD risk.

Triglycerides, another blood fat, come from the diet and are also produced in the liver. When very elevated, triglycerides can cause pancreatitis and can also increase the risk of developing CHD.

Is there FH in my Family?

FH is inherited as an autosomal dominant disorder. This means that if you inherit a single gene for FH, then you will have a very high LDL-C level. The closest relatives of people with FH (parents, brothers and sisters, children) all have a 50% chance of also having FH. In families with FH, there generally is a pattern of people with very high cholesterol and early heart disease. In families with FH, it is not uncommon for people to have heart attacks in their 50s, 40s, 30s, or even 20s. In fact, the risk of early heart disease is about 20 times higher in people with untreated FH than in the general population.

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How common is FH?

FH is one of the most common genetic (or inherited) life-threatening disorders. It affects at least 1 out of every 500 people worldwide. Although FH occurs in all populations, some ethnic groups are disproportionately impacted. These include people of Lebanese, French Canadian, South African Afrikaner, and Ashkenazi Jewish descent. In these populations FH may be found as frequently as 1 in every 80-100 people.
 

Do I have FH?

FH is a serious disorder. If left untreated, FH leads to premature heart disease. Yet for most people with FH, until they experience a heart attack, there are few physical signs or symptoms.Some people will develop cholesterol deposits in specific locations including: the Achilles tendons (the back of the ankle) and the tendons of the hands. These are called tendon xanthomas.

Some people develop orange or yellow fatty deposits around the eyes called xanthelasmas. Cholesterol may also deposit in the clear outer covering (cornea) of the eye. This usually occurs in the shape of a half moon (arcus).

Unfortunately, these are not always recognized by treating clinicians as signs of FH . It is also quite possible for a person to have FH without any of the aforementioned physical findings. In general, the older a person is, the more likely they are to manifest some signs.

Many individuals with FH feel and look healthy, yet their arteries may be significantly diseased. If you have a family history of early heart disease or death from cardiac events, as well as an LDL-cholesterol level over 190 mg/dL, then you need to work with your clinician to rule out FH as the cause. In the United States it is estimated that only 20% of individuals with FH have been properly diagnosed.

What can I do?

FH is treatable! If FH is found early, serious problems of the heart and blood vessels may be prevented or delayed by taking steps to protect your heart.These include:
  • Not smoking.
  • Exercising regularly.
  • Eating a healthy diet low in saturated and trans fats.
  • Taking medications.
Nearly 100% of people with FH will require cholesterol-lowering medications. For some people with FH, more heroic measures are needed, including LDL-apheresis (a dialysis-like procedure in which LDL-C cholesterol is removed from the blood on a weekly or biweekly basis.) The American Academy of Pediatrics recommends that if a family has a pattern of early heart attacks or heart disease defined as before age 55 for men and 65 for women, children in that family should have cholesterol testing after the age of 2 years and before age 10. It is important to find FH and take action at any age, because when treated, the risk of heart disease can be reduced to levels similar to those of the general population.