Hereditary coagulation conditions – increased risk of blood clots?

Many people first hear about hereditary clotting conditions when someone in the family suffers from a blood clot at a young age, when a pregnancy needs to be monitored extra carefully, or when questions arise before taking the pill, having surgery, or going on a long trip. This can raise both concerns and many practical questions: Is this something I could have too? Do I need to get tested? And what does a positive test result actually mean? Hereditary clotting conditions mean that you have an innate tendency to form blood clots in your veins more easily, but that does not automatically mean that you will get sick. The risks are also affected by things like pregnancy, estrogen treatment, surgery, infection, immobilization, and smoking.

What are hereditary clotting conditions?

Hereditary clotting conditions are often also called hereditary thrombophilia. This refers to genetic changes that increase the tendency of blood to clot in the veins. The most important clinical consequence is an increased risk of venous thromboembolism (VTE), namely:

• Deep vein thrombosis (DVT) – blood clot in a deep vein, usually in the leg

• Pulmonary embolism (PE) – when a clot or part of a clot blocks the vessels of the lungs

The most common hereditary forms are:

• Factor V Leiden

• Prothrombin mutation (F2 G20210A)

• Antithrombin deficiency

• Protein C deficiency

• Protein S deficiency

Factor V Leiden is the most common hereditary thrombophilia. Heterozygous form occurs in approximately 3–8% of the population in the US and Europe, while antithrombin, protein C and protein S deficiency are considerably less common.

It is important to understand that such a condition is not the same as an ongoing disease. Many people with hereditary thrombophilia never develop any blood clot. Therefore, a test result should always be interpreted together with the person's own medical history, family history and other risk factors. Several guidelines emphasize that routine screening of the entire population or of asymptomatic relatives is rarely helpful.

What symptoms and complications can you get?

Hereditary thrombophilia itself usually does not cause any daily symptoms. What is noticeable instead is if a blood clot occurs.

Common signs of deep vein thrombosis are:

• swelling in a leg

• pain or tenderness in the calf or thigh

• redness or warmth

• a feeling of heaviness in the leg

Common signs of pulmonary embolism are:

• sudden shortness of breath

• chest pain, often when taking a deep breath

• cough, sometimes with blood

• palpitations or a feeling of fainting

These are acute symptoms that should be assessed quickly.

Classic hereditary coagulation conditions (thrombophilias) are primarily linked to a increased risk of venous blood clots, for example in the legs or lungs. However, they are not strongly associated with arterial events such as heart attacks or most forms of ischemic stroke. For this reason, thrombophilia tests are not normally included in the routine examination after a heart attack or a common stroke, since genetic factors are rarely the cause of these conditions.

Another common question concerns pregnancy. Pregnancy and especially the period after childbirth inherently increase the risk of venous thrombosis. In women with certain hereditary thrombophilias, especially if there is also a personal or strong family history of clots, there may be a need for more frequent assessment and sometimes preventive treatment.

Why is the risk of blood clots increased?

The body normally has a carefully regulated balance between things that form clots and things that slow down clot formation. In hereditary coagulation conditions, this balance is disrupted.

Here is a simplified explanation:

• Factor V Leiden causes coagulation factor V to become less sensitive to the body's natural braking system, activated protein C.

• Prothrombin mutation can lead to higher levels of prothrombin, a protein needed to form a clot.

• Antithrombin, protein C and protein S deficiency means that the body's natural "anticoagulants", i.e. clot-inhibiting mechanisms, function less well.

But genetics is only part of the picture. Often, a blood clot is triggered when the hereditary predisposition is combined with other risk factors, for example:

• surgery or trauma

• prolonged sitting or cast placement

• pregnancy and postpartum period

• birth control pills or other estrogen therapy

• cancer

• older age

• obesity

• smoking

That is why two people with the same genetic variant can have completely different disease patterns. One never gets a clot, while the other gets a DVT after surgery, air travel or pregnancy.

When should you be tested for hereditary clotting conditions?

According to modern guidelines, thrombophilia testing is most relevant when the result can actually affect treatment, risk assessment or counseling. For example, it may be relevant in the following cases:

• venous blood clot at a young age

• repeated blood clots

• blood clot without a clear triggering factor

• blood clot in an unusual location, for example in the veins of the brain or abdomen

• strong family history with several close relatives who have had venous clots

• certain questions regarding pregnancy, postpartum or estrogen treatment

• known specific thrombophilia in the family where the answer may affect medical decisions

However, several guidelines advise against broad screening in people without their own clotting disease and without a clear risk profile. The reason is that a positive finding does not always change treatment, but can create concern and lead to overinterpretation.

An important practical detail is when to test. Protein C, protein S and antithrombin can be affected by acute blood clots, pregnancy and certain medications, especially warfarin and heparin. Therefore, investigations should often be done only after the acute phase has passed and at the right time in relation to any anticoagulant treatment. Genetic tests for factor V Leiden and prothrombin mutation, however, are not affected in the same way by an acute episode.

For those wondering: “Should I get tested just because a relative has factor V Leiden?” The answer is usually that it requires individual assessment. Asymptomatic family members are not routinely screened, but testing can sometimes be considered if the result is expected to affect the choice of contraception, pregnancy planning or other risky situation.

How are the problems treated and prevented?

Treatment is primarily directed at the blood clot disease, not at the gene variant itself. If a person gets a DVT or pulmonary embolism, this is usually treated with anticoagulants, i.e. blood-thinning drugs. How long the treatment should last depends on the whole: whether the clot was provoked or unprovoked, whether it has recurred, whether there is strong thrombophilia and whether the risk of bleeding is low or high.

It is also important to know that a genetic abnormality does not automatically mean lifelong treatment. For example, people with heterozygous factor V Leiden or heterozygous prothrombin mutation usually do not need to be on lifelong anticoagulation solely because of the test result.

Preventive measures are often at least as important as medication. This may involve:

• avoiding smoking

• staying physically active

• reducing prolonged sitting

• discussing birth control pills or hormone therapy with healthcare providers

• getting the right thrombosis prophylaxis during surgery or hospital care

• planning pregnancy and postpartum follow-up if risk factors exist

In practice, good healthcare often involves combining three things:

1. Correct risk assessment

2. Right time for testing

3. Right action based on the individual's situation

This means that testing only becomes meaningful when it is used in a medical context.

This is good to know about hereditary coagulation condition

Many people who carry a hereditary coagulation condition are completely healthy and never develop a blood clot. The actual risk is influenced by both genetic factors and life situations, such as pregnancy, surgery, prolonged periods of sitting still or hormone therapy.

When investigating hereditary thrombophilia, tests for common MTHFR variants are no longer included, as these are not considered to provide a meaningful basis for assessing the risk of venous blood clots. However, if you have a personal or strong family history of blood clots, it is important to discuss contraception with your healthcare provider, as estrogen-containing birth control pills can increase the risk of venous thromboembolism.

Physical activity is in most cases positive and an important part of preventive health work. However, in the event of an ongoing blood clot or during treatment, the advice may need to be adapted to the individual situation. During pregnancy, an individual assessment of the need for blood-thinning treatment is always made based on the type of thrombophilia present, previous blood clots and other risk factors.

Understanding hereditary coagulation conditions is therefore not just about the results of a genetic test, but about seeing the whole risk picture. For some, knowledge is particularly important before pregnancy, surgery or hormone therapy, while for others it is mainly about recognizing the symptoms of blood clots and working preventively together with healthcare.