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Antithrombin Deficiency Resources

A Genetic or Acquired Clotting Condition or Thrombophilia

If you have antithrombin deficiency (AT), you were either born with it and it is an inherited or genetic clotting disorder, or you acquired it. If you have the genetic or inherited form, you are at an increased risk of getting a blood clot.

Antithrombin is a protein in your blood stream, which functions as a naturally occurring mild blood thinner or or anticoagulant. It acts like a police protein that prevents you from clotting too much. It blocks your blood clotting mechanism by turning off the major clotting protein called thrombin. It is, therefore, called anti-thrombin. While originally called “antithrombin III,” the correct name now is just antithrombin, without the “III.” Other common names and abbreviations for the same protein include antithrombin, antithrombin III, AT, ATIII, and heparin cofactor I.

Signs and Symptoms of Blood Clots: What You Need to Know

Since you are at risk of blood clots if you have AT, you need to be aware of the symptoms of deep vein thrombosis (DVTs or leg or arm clots) so you can seek medical attention.

If you have a DVT you will notice:

Pain or tenderness in your arm or leg – often described as a cramp or charley horse – with one or more of the following:

Swelling
Red or purple skin color
Skin that is warm to the touch

If a piece of a DVT breaks off and travels to the lung, it can cause a lung clot. We call this a pulmonary embolism or PE. A PE can be a life threatening medical emergency. You need to seek immediate medical attention if you have symptoms of a PE.

If you have a pulmonary embolism or PE, you may experience:

Difficulty breathing or shortness of breath
Chest pain, especially when trying to breathe
Rapid or racing heart beat
Fainting or passing out
Coughing up blood

Resources for More Information

You can read more about Antithrombin Deficiency at these links below:

Antithrombin Deficiency (AT)- An In-Depth Guide for Patients and Healthcare Providers (2024): An easy to understand article that explains the symptoms, causes, diagnosis, and treatment of AT, including a discussion of AT during pregnancy.
Antithrombin Deficiency (2018): A report by Kenneth A. Bauer, MD, Professor of Medicine, Harvard Medical School and former member of NBCA’s Medical and Scientific Advisory Board and the National Organization for Rare Disorders (NORD.) Provides information on the symptoms, causes, and treatment of AT.
Congenital antithrombin III deficiency (2023): A plain language explanation of the causes, symptoms, and treatment of AT. From Medline Plus, the National Institutes of Health
Hereditary antithrombin deficiency (2013): A plain language explanation of hereditary AT with a focus on the genetics of AT. Part of the Genetics Home Reference Series from the National Institutes of Health.
Antithrombin Deficiency (2022): A technical article that describes the study of the history of the first family with AT and the pathophysiology and epidemiology of AT from Medscape.
Inherited antithrombin deficiency (2008): A technical article on AT that reviews detailed information about the different types of AT as well as evaluation approaches and treatment.
Deficiencies of Natural Anticoagulants, Protein C, Protein S, and Antithrombin (2011): A patient-focused article on deficiencies in the natural anticoagulants or blood thinner including antithrombin. Discusses causes, diagnosis, treatment, complications, and testing.
Antithrombin Testing (2016): Answers the questions: How is it used? When is it ordered? What do the test results mean? Is there anything else I should know? From the American Association for Clinical Chemistry.