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Factor II


What is it?

(Can also be known as prothrombin deficiency)


Factor II deficiency is quite rare, with only 26 cases reported in the medical literature. The incidence is estimated at 1 in 2 million. It is inherited in an autosomal recessive fashion, which means it affects men and women equally.


Prothrombin is a precursor to thrombin, which converts fibrinogen into fibrin which in turn strengthens a protective clot. Factor II deficiency usually takes the form of an abnormality in the structure of prothrombin rather than a lack of the protein itself. People with a more severe factor II deficiency have severe bruising, bleeding from the nose and mouth, menorrhagia, as well as muscle bleeds, head bleeds and bleeding after trauma. Joint bleeding is rare.

Diagnosis is made with a prothrombin time (PT) test and an activated partial thromboplastin time (aPTT) test. Levels of prothrombin deficiency can range from 2% to 50% of normal. Patients with levels reaching 50% of normal have little to no bleeding problems.


The inherited condition must be distinguished from the acquired form of Factor II, which is also associated with bleeding. Hereditary Factor II deficiency has also been reported as part of a combined disorder with factor VII, IX, X and protein C and S.



Moderate bleeding can be treated with Fresh Frozen Plasma. Correction of prothrombin can also be achieved with the use of Prothrombin complex concentrates (PCCs). However, there are differences in the amount of factor II present in PCCs, depending upon the product. There are reported risks of thromboembolic complications with certain use of PCCs.


–Information by the National Hemophilia Foundation

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