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Factor I Deficiency

What is it?

(can also be known as Fibrinogen deficiency, afibrinogenemia, dysfibrinogenemia, or hypofibrinogenemia)


Factor I deficiency is actually a collective term for several rare inherited fibrinogen deficiencies. Fibrinogen may be absent from the blood altogether (afibrinogenemia), present in only very low levels in the blood (hypofibrinogenemia), or measurable in normal quantities but defective (dysfibrinogenemia).


The incidence of Factor I deficiency is estimated at 1 to 2 per million. It is inherited in an autosomal recessive fashion, which means it affects men and women equally.


Fibrinogen helps platelets to glue together to form the initial “plug” in response to an injury. Therefore, people with factor I deficiency, have a combined bleeding disorder because both platelets and clotting are abnormal. The severity of the disorder is directly related to the amount of fibrinogen present.

Afibrinogenemia and hypofibrogenemia are usually diagnosed in newborns who can present with head bleeds, bleeding after circumcision and from the site of the umbilical cord. Easy bruising, nose and mouth bleeds, and soft tissue bleeds are also common. Joint bleeding is relatively uncommon. Women with afibinogenemia have an increased risk of spontaneous abortion. Persons with dysfibrinogenemia may have a disposition to thrombosis.


Diagnosis is made by measuring the amount of fibrinogen in the blood, prothrombin time (PT) test, activated partial thromboplastin time (aPTT) test, and thrombin clotting time (TCT) test.



For now, cryoprecipitate is the treatment of choice in the United States. FFP may be given, but cryoprecipitate is used more often to avoid volume overload. There are no Factor I concentrates available for use in the U.S. However, there are three fibrinogen concentrates being used in Europe and Japan. There have also been some reports of adverse reactions with use of these concentrates.

–Information by the National Hemophilia Foundation

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