Factor I Deficiency

(Also known as Fibrinogen Deficiency, Afibrinogenemia, Dysfibrinogenemia or Hypofibrinogenemia)

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.

Factor I deficiency is actually a collective term for several rare inherited fibrinogen deficiencies:

  • Fibrinogen may be absent from the blood altogether (Afibrinogenemia)
  • Fibrinogen may be present in only very low levels in the blood (Hypofibrinogenemia)
  • Fibrinogen may be measurable in normal quantities but defective (Dysfibrinogenemia)


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
  • With 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.


Cryoprecipitate is a treatment option for factor I deficiency in the United States. FFP may be given, but cryoprecipitate is used more often to avoid volume overload. RiaSTAP is a fibrinogen concentrate available in the United States and has been used on patients at BCDI.