What is familial hypercholesterolemia?
In cholesterol levels, there are very different factors: race, geographical origin, diet, lifestyle, etc. The main factor, however, is genetic influence or inheritance. This is the reason why several people with high cholesterol can be found in the same family. There is an inherited form that produces slight elevations of the levels (polygenic hypercholesterolemia), but when there are many relatives with very high cholesterol, a metabolic disease, such as Familial Hypercholesterolemia (FH), must be suspected.
The FH is due to a genetic defect that affects elements of the surface of the cells, called LDL (low density lipoprotein) receptors, because they are responsible for the uptake of this form of cholesterol. It is enough that only one of the parents transmits the disease, so that it is manifested, which happens in approximately one in 500 people (it is called the heterozygous form). Much more rare is that both parents transmit the disease (homozygous form), in which case the disease is very serious and manifests itself at young ages.
The disease is transmitted from generation to generation, so that the siblings and children of a person with FH have a 50% risk of suffering from FH. However, it does not skip generations, i.e. the children and grandchildren of families who do not have a defective gene are not at risk of FH.
In this disease, the blood cholesterol level is above normal values from birth and produces a premature appearance of arteriosclerosis and vascular diseases.
This condition is usually treated with an adequate diet and often also requires the use of medications. The possibility of treatment with genetic manipulation is still a promise of the future. The following degrees of hypercholesterolemia are considered:
- Ideal level: less than 200 mg / dl
- Cholesterol slightly elevated: between 200 and 240 mg / dl
- Moderately elevated cholesterol: between 240 and 300 mg / dl
- Very high cholesterol: above 300 mg / dl.
What is the cause of FH?
All cells in the body, but more markedly in the liver, have on their surface some elements or receptors that serve to collect the cholesterol that is transported in the blood in particles called low density lipoprotein (LDL).
People with FH have a defect in the DNA of the gene that produces the production of these receptors. For this reason, LDL cholesterol, which cannot be withdrawn from the blood, accumulates and levels rise. It eventually deposits in the walls of the arteries, which speeds up the process of atherosclerosis.
The genetic mechanisms for the manufacture of the LDL receptor are very well known and more than 300 different genetic failures have been identified which give rise to an FH.
Are there other causes for elevating cholesterol?
In addition to FH and polygenic hypercholesterolemia, there are other hereditary diseases that evolve with elevations, sometimes important, of LDL cholesterol. Among them, we can highlight the combined familial hyperlipidemia (relatively frequent) and dysbetalipoproteinemia (rare); In both are also high triglycerides, another of the fats or lipids of the body.
On the other hand, excess weight, lack of exercise, a diet rich in animal fat and some medications also promote the elevation of cholesterol levels.
The average levels of cholesterol in the population are higher in the countries of northern Europe and North America than in the southern ones, such as Spain. In Asia they are still much smaller.
In some cases high cholesterol levels may be a symptom of other diseases such as:
- Hypothyroidism (lack of thyroid hormone)
- Kidney diseases
- Liver diseases
What are the symptoms of FH?
People with FH may not be at all aware that they have a high cholesterol level.
In many cases, however, close observation by the physician can detect cholesterol deposits in the eye, in the form of a ring in the iris, or on the skin of the eyelids and tendons (eg the Achilles tendon ), As white-yellowish plaques, somewhat prominent and of variable size.
Another indicator of possible FH is the history of several relatives with high cholesterol or coronary heart disease at an early age (before age 55 in men or age 65 in women). Sometimes they learn of their disease when they already have symptoms of cardiovascular disease, which develop as a result of a process of arteriosclerosis. This is very slow and, in fact, begins in childhood or adolescence. It can be compared to calcium deposits in a water pipe, whereby, gradually, the opening becomes smaller and smaller and the inner surface becomes more irregular. Similarly, when artery lesions are highly developed, blood cannot circulate freely and symptoms occur. When the blood supply to a tissue is totally interrupted, death or necrosis occurs.
The disease is especially severe when the coronary arteries are affected and there is a heart attack; the symptoms may consist of Oppressive pain in the center of the chest, which appears after physical exertion or exposure to cold and can extend to the arm or neck (angina).
The same more intense and prolonged symptoms may indicate that acute coronary thrombosis is taking place, which triggers an acute myocardial infarction. This is because the area of cardiac muscle that was being supplied by the obstructed vessel suffers an irreversible injury, after which a fibrous scar is formed, and the heart is weakened.
How does the doctor make the diagnosis?
A blood test is required after a 12-hour fast (in which only water can be drunk). In the sample, the levels of total cholesterol, LDL cholesterol (known as bad cholesterol), HDL cholesterol (known as good cholesterol) and blood triglycerides are measured. The results suggest an FH if LDL cholesterol levels are very high and triglycerides are normal, without data from another associated disease. In addition, the above-mentioned external cholesterol deposits, and family history with elevated cholesterol and / or premature cardiovascular disease, are very typical of FH. In specialized centers the diagnosis can be confirmed by genetic tests. If LDL cholesterol levels and triglycerides are both increased, a combined familial hyperlipemia is more likely to occur.
For an adequate assessment of cholesterol levels, consideration should be given to their rise with age and in men. It also rises during pregnancy and falls significantly, although transient (1-3 months), after a major illness, such as a myocardial infarction.
Finally, it is necessary for the physician to identify the possible data of a developed cardiovascular disease, by examining the heart, the arterial pulses and the blood pressure. Sometimes, when the suspicion of coronary lesions is high, an exercise test is also done, in which changes in the heart are studied, when the person is submitted to the practice of physical exercise.
What can a person diagnosed with FH do?
In FH, high cholesterol is the most important risk factor for developing arterial disease. However, other factors also influence this process. Therefore, it is important to acquire an adequate lifestyle from childhood and to maintain it during adulthood.
You should follow a diet rich in bread, vegetables, fruits, vegetables, blue fish and olive oil, and limit the consumption of non-skimmed dairy products, meat and by-products.
In adulthood, moderate consumption of red wine can be accepted as it increases HDL cholesterol and may reduce the negative effect of LDL cholesterol. This consumption is not advisable if there is hypertension, elevation of triglycerides or other diseases that are aggravated by alcohol.
It is very important, if you are a smoker, to quit. In patients with severe hypercholesterolemia, smoking significantly increases the risk of coronary heart disease.
Maintaining an active lifestyle and regular physical exercise strengthen the heart and reduce the risk of cardiovascular disease.
How is FH treated?
Although you should always follow the diet described, it is difficult to normalize cholesterol levels only with changes in diet. Therefore, it is often necessary to follow a drug treatment, in addition to changes in lifestyle.
The most effective medications at present are statins, which decrease the production of LDL cholesterol in the liver. Thus, blood levels of this type of cholesterol can be reduced up to 50%.
Another medication that is used are the ion exchange resins, which favors the elimination of the cholesterol contained in the bile by the intestine. These are the only drugs that are recommended for use in children and adolescents.
It may be necessary to associate both types of drugs or combine them with fibrates.
Very severe cases of homozygous FH require other measures such as plasma clearance (plasmapheresis).
Both children and adults with suspected FH should see a lipid specialist to confirm the diagnosis and decide the most appropriate treatment in each case.
What is the prognosis of FH?
The natural evolution of FH varies greatly; However, in members of the same family tends to follow a similar course.
Without proper treatment, the risk of dying from myocardial infarction before age 40 in people with FH is much higher than in the general population and approximately one-third of patients do not have any symptoms until they suffer from cardiac death Sudden It has been estimated that up to 50% of men and 40% of women with untreated FH have experienced acute coronary thrombosis before age 60.