Factor I Deficiency

Factor I deficiency, also known as fibrinogen deficiency, is a rare inherited bleeding disorder related to fibrinogen function in the blood coagulation cascade. It is typically subclassified into three distinct disorders: afibrinogenemia, hypofibrinogenemia, or dysfibrinogenemia. Afibrinogenemia is defined as a lack of fibrinogen in the blood, clinically <20 mg/deciliter of plasma. The frequency of this disorder is estimated at between 0.5 and 2 per million. Hypofibrinogenemia is defined as a partial deficiency of fibrinogen, clinically 20–80 mg/deciliter of plasma. Estimated frequency varies from <0.5 to 3 per million. Dysfibrinogenemia is defined as malfunctioning or non-functioning fibrinogen in the blood, albeit at normal concentrations: 200–400 mg/deciliter of plasma. Hypodysfibrinogenemia is a partial deficiency of fibrinogen that is also malfunctioning. Estimated frequency varies from 1 to 3 per million. Within the United States, afibrinogenemia accounts for 24% of all inherited abnormalities of fibrinogen, while hypofibrinogenemia and dysfibrinogenemia account for 38% each.