What is thrombophilia?

Thrombophilia (also known as hypercoagulability) is a predisposition to the development of blood clots. Thrombophilia can be either inherited or acquired during one’s lifetime. Conditions leading to thrombophilia that can be acquired or develop during one’s lifetime include abnormalities of the blood such as too many red blood cells (polycythemia) or too many platelets (thrombocytosis or thrombocythemia), placement of a mechanical heart valve, or the development of abnormal proteins or antibodies.

Inherited thrombophilia was first described in the 1960s, when researchers discovered the existence of antithrombin deficiency. Antithrombin is a natural anticoagulant that blocks both the conversion of prothrombin to thrombin and the conversion of factor X to its active form, factor Xa. (See Question 18.) Protein C and protein S deficiencies were described in the 1980s. Protein C and protein S are natural anticoagulants that, in combination with each other, degrade or destroy factor V. In the 1990s, factor V Leiden and a


A change in a gene from its natural state. Mutations may cause disease or result in a normal variant that causes no problems for the patient.


The blueprints for making individual proteins, located in the DNA. The human genome codes for an estimated 20,000 to 25,000 individual genes.

mutation in the prothrombin gene were also described.

Dena’s story:

After I had emergency surgery for dead bowel caused by a blood clot that had formed in my superior mesenteric vein (a vein in the intestines) and was also found to have small clots that had formed in both common femoral veins (the veins in my groin), a hematologist was called in. After running some tests, he discovered that I had a rare hereditary blood disease called protein S deficiency.

I was put on lifelong Coumadin®. I have my PT and INR checked monthly at a local lab, and after being on Coumadin® for 15 years, I am at a therapeutic level and live a very normal life. I have researched this blood disease, and have since found out that several family members on my mother’s side also have it. Some have been put on various blood thinners, and others are on aspirin therapy. I am so thankful that my condition was discovered in time, and that I am knowledgeable and prepared in case this disease is passed along to my daughter.

Current News

Introducing the NBCA Advocacy Institute

To put an end to the 100,000 deaths each year to blood clots, the National Blood Clot Alliance is accelerating…

NBCA Journal Club Convenes to Discuss Antithrombin Therapy

Launched last year, the NBCA Journal Club highlights groundbreaking research in thrombosis and thrombophilia and features a manuscript author as…