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Prothrombin thrombophilia
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Prothrombin thrombophilia

Prothrombin thrombophilia is a genetic disorder that increases the risk of developing blood clots, particularly deep vein thrombosis and pulmonary embolism, due to the overproduction of prothrombin.

Overview

Prothrombin thrombophilia is a disorder that increases the risk of developing blood clots. Thrombophilia is the term used to describe an increased tendency to form blood clots. After an injury, clots protect the body by sealing off damaged blood vessels and preventing further blood loss. People with thrombophilia can develop clots when they are not needed. These clots can block normal blood flow and cause harm.

People who have prothrombin thrombophilia have a higher-than-average risk of developing a type of clot called a deep vein thrombosis (DVT), which typically occurs in the blood vessels of the arms or legs. People with prothrombin thrombophilia also have an increased risk of developing a pulmonary embolism (PE), which is a clot that travels through the bloodstream and lodges in the lungs.

Research suggests that pregnancy loss may be somewhat more likely in people with prothrombin thrombophilia than in those who do not have the condition. Some researchers have suggested that prothrombin thrombophilia may also increase the risk of other complications during pregnancy, though this remains controversial.

While many people with prothrombin thrombophilia will never have clotting issues, several factors increase a person's risk of blood clots. Some risk factors that contribute to the development of harmful blood clots include surgery, injury or trauma, air travel, obesity, and a family history of blood clots. Additional risk factors include pregnancy, using contraceptives such as birth control pills or patches that contain estrogen, and receiving post-menopausal hormone replacement therapy. The combination of prothrombin thrombophilia and other clotting disorders may also increase a person's risk.

Frequency

Prothrombin thrombophilia is the second most common inherited form of thrombophilia after factor V Leiden thrombophilia.

Prothrombin thrombophilia is most common in people of European ancestry. Two to five percent of Americans of European ancestry have the particular genetic variant (also called a mutation) that causes most cases of prothrombin thrombophilia. This condition is much less common in African, Asian, and Native American populations.

Causes

A particular variant in the F2 gene causes most cases of prothrombin thrombophilia. The F2 gene plays a critical role in the formation of blood clots in response to injury. The protein produced from the F2 gene is called prothrombin (also known as coagulation factor II). Prothrombin is the precursor to a protein called thrombin that initiates a series of chemical reactions to form a blood clot.

The variant in the F2 gene that causes most cases of prothrombin thrombophilia triggers the production of too much prothrombin. More prothrombin leads to more thrombin, which promotes the formation of blood clots.

Associated Genes

  • F2

Inheritance

Prothrombin thrombophilia is typically inherited in an autosomal dominant, which means one copy of the altered gene in each cell is sufficient to increase the risk of developing harmful blood clots.

Individuals who have a variant in one of the two copies of the F2 gene have a risk of developing harmful blood clots that is two to five times greater than average.

Because the F2 gene variant that causes most cases of prothrombin thrombophilia is common in certain populations, it is possible for an individual to inherit this variant from both parents. Though many people who inherit a variant in both copies of their F2 gene will never develop a harmful blood clot, these individuals have a higher risk than people who inherit only one F2 gene variant. People with two F2 gene variants may also develop harmful blood clots more frequently and at a younger age than people with just one F2 gene variant.

Other Names

  • Prothrombin G20210A thrombophilia
  • Prothrombin-related thrombophilia
  • Thrombophilia 1 due to thrombin defect

Frequently Asked Questions

Prothrombin thrombophilia may increase the risk of pregnancy complications, including a slightly higher chance of pregnancy loss. While some research suggests other complications, this is still debated. If you are pregnant or planning to become pregnant, it's crucial to discuss your condition with your obstetrician and a hematologist. They may recommend close monitoring or preventive measures, such as blood-thinning medication, to reduce the risk of clots during pregnancy and the postpartum period.
For a deep vein thrombosis (DVT), watch for swelling, pain, tenderness, warmth, or redness in one leg or arm. For a pulmonary embolism (PE), symptoms include sudden shortness of breath, chest pain that worsens with deep breaths, coughing (sometimes with blood), rapid heart rate, or dizziness. Seek immediate medical attention if you experience any of these symptoms.
To reduce your risk, maintain a healthy weight, stay active, and avoid prolonged periods of immobility, especially during long travel. If you're recovering from surgery or injury, follow your doctor's instructions for movement and any prescribed blood thinners. Discuss your condition with your doctor before starting estrogen-containing contraceptives or if you plan to become pregnant, as these can increase clot risk.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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