What are the symptoms of antithrombin deficiency?

September 21, 2025 •

3 min read

Antithrombin deficiency is a rare genetic disorder affecting an estimated 1 in 2,000 to 3,000 individuals. This condition can lead to abnormal blood clotting, but many people are unaware of the warning signs. It is crucial to understand what are the symptoms of antithrombin deficiency to ensure a proper diagnosis and management plan.

Quick Summary

Antithrombin deficiency is a blood clotting disorder that can lead to deep vein thrombosis (DVT) and pulmonary embolism (PE). Symptoms are related to these clots and include pain, swelling, and redness in a leg or arm, as well as severe chest pain, shortness of breath, or a rapid heart rate.

Key Points

Blood Clots are the Main Symptom: The most noticeable symptoms arise from abnormal blood clots, especially deep vein thrombosis (DVT) and pulmonary embolism (PE).
Look for DVT Signs: Symptoms of DVT include pain, swelling, redness, and warmth in a leg or arm.
Watch for PE Warning Signs: A pulmonary embolism is a medical emergency with symptoms like sudden shortness of breath, chest pain, and rapid heart rate.
Inherited or Acquired: Antithrombin deficiency can be inherited genetically or acquired due to other conditions like liver or kidney disease.
Early Detection is Crucial: Diagnosis involves specific blood tests and careful interpretation to differentiate from other causes of low antithrombin.
Management is Long-Term: Treatment typically involves ongoing anticoagulant medication to prevent future blood clots.

Understanding Antithrombin Deficiency

Antithrombin is a protein in the blood that helps prevent excessive clotting. When there is a deficiency, either due to insufficient amount or function, the risk of developing blood clots, specifically deep vein thrombosis (DVT) and pulmonary embolism (PE), increases. This condition can be inherited through genetics or acquired from other health issues like liver disease or certain medications. Understanding the cause is important for proper management.

The Primary Symptoms of Antithrombin Deficiency

Symptoms of antithrombin deficiency are primarily related to the formation of blood clots (DVT and PE). The first clot often occurs in adulthood and can be triggered by factors such as surgery, immobility, or pregnancy.

Symptoms of Deep Vein Thrombosis (DVT)

DVT commonly occurs in the legs but can affect other areas. Signs include:

Pain or tenderness, often described as a cramp.
Swelling in the affected limb.
Redness or discoloration of the skin.
Warmth in the affected area.

Symptoms of Pulmonary Embolism (PE)

PE is a serious condition where a clot travels to the lungs. It requires immediate medical attention. Symptoms include:

Sudden difficulty breathing.
Sharp chest pain, which may worsen with deep breaths.
Rapid or irregular heartbeat.
Coughing, sometimes with blood.
Fainting or dizziness.

Diagnosis of Antithrombin Deficiency

Diagnosing antithrombin deficiency involves medical history, physical exam, and lab tests. Testing is often done when there is no acute clot or heparin use to ensure accurate results.

Key steps include:

Reviewing personal and family history of clotting disorders.
Initial activity assay to check how well antithrombin functions, helping detect both Type I and Type II deficiencies.
If activity is low, an antigen assay measures the amount of antithrombin. The ratio helps classify the deficiency type.
Testing for other clotting disorders may also be performed.
Genetic testing of the SERPINC1 gene can confirm a hereditary diagnosis.

Comparing Antithrombin Deficiency with Other Thrombophilias

Antithrombin deficiency is one of several inherited conditions that increase clotting risk. Below is a comparison:


Feature	Antithrombin Deficiency	Protein C Deficiency	Protein S Deficiency
Prevalence	Approx. 1 in 2,000–5,000.	Approx. 1 in 200–500.	Approx. 1 in 200–500.
Inheritance	Autosomal dominant.	Autosomal dominant.	Autosomal dominant.
Inherited Risk	Higher risk of venous thrombosis.	Moderate risk, often with other factors.	Moderate risk, often with other factors.
Mechanism	Impaired antithrombin function or production.	Reduced function or levels of Protein C.	Reduced function or levels of Protein S.
Diagnosis	Activity assay followed by antigen test.	Activity test over antigen for Type II.	Total and free Protein S tests.

Treatment and Management

Preventing blood clots is the main goal. This often involves long-term use of anticoagulant medications like heparin, warfarin, or DOACs. In high-risk situations such as surgery, antithrombin concentrate may be used. Individuals should also take precautions during periods of prolonged immobility.

Conclusion: Recognizing the Signs is Key

Recognizing the symptoms of DVT and PE is vital for individuals with or at risk for antithrombin deficiency. Early detection can prevent serious complications. Understanding the type of deficiency and triggers for clots aids in management. Always consult a healthcare professional for diagnosis and treatment if you suspect a blood clot.

For more detailed information on antithrombin deficiency and other thrombophilias, please visit the National Organization for Rare Disorders (NORD) website.

Frequently Asked Questions

Antithrombin deficiency is a disorder where the body either produces too little antithrombin, a protein that regulates blood clotting, or produces a form that doesn't function correctly.

Yes, symptoms can vary. Many people with inherited deficiency don't have symptoms until later in life, and some may never have a thrombotic event. The severity and location of a blood clot determines the symptoms experienced.

Risk factors include advanced age, surgery, prolonged immobility, pregnancy, and the use of oral contraceptives or hormone replacement therapy.

Diagnosis is typically made through specialized blood tests. A functional activity assay is used to measure protein function, and if it is low, an antigen assay measures the protein's quantity. Genetic testing can provide definitive confirmation.

In some cases, yes. If the acquired deficiency is caused by an underlying condition like liver disease or nephrotic syndrome, levels may improve once the primary condition resolves or is managed.

Hereditary antithrombin deficiency is an inherited genetic disorder caused by a mutation in the SERPINC1 gene. It is typically passed down in an autosomal dominant pattern.

The main treatment involves taking anticoagulant medications (blood thinners) to prevent blood clots. In high-risk situations like surgery, antithrombin concentrate may be administered.