Factor I deficiency, also known as

fibrinogen Fibrinogen (factor I) is a glycoprotein complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted enzymatically by thrombin to fibrin and then to a fibrin-based blood ...

deficiency, is a rare inherited bleeding disorder related to fibrinogen function in the blood coagulation cascade. It is typically subclassified into four distinct fibrinogen disorders: afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia, and hypodysfibrinogenemia. * 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. Within the United States, afibrinogenemia accounts for 24% of all inherited abnormalities of fibrinogen, while hypofibrinogenemia and dysfibrinogenemia account for 38% each. *

Congenital hypofibrinogenemia Congenital hypofibrinogenemia is a rare disorder in which one of the three genes responsible for producing fibrinogen, a critical blood clotting factor, is unable to make a functional fibrinogen glycoprotein because of an inherited mutation. In con ...

is defined as a partial deficiency of fibrinogen, clinically 20–80/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. Dysfibrinogenemia may be an inherited disease and therefore termed congenital dysfibrinogenemia or secondary to another disease and therefore termed acquired dysfibrinogenemia. The congenital disorder is estimated to a frequency varying between 1 and 3 per million. * Hypodysfibrinogenemia is a partial deficiency of fibrinogen that is also malfunctioning. Hypodysfibrinogenemia is an extremely rare inherited disease. Clinically, these disorders are generally associated with an increased

diathesis Diathesis (from the Greek διάθεσις "grammatical voice, disposition") may refer to: *Grammatical voice *Diathesis (medical), a hereditary or constitutional predisposition to a disease or other disorder ** Predisposition (psychology) ***The d ...

, i.e. propensity, to develop spontaneous bleeding episodes and excessive bleeding after even minor tissue injuries and surgeries; however, individuals with any of these disorders may also exhibit a propensity to pathological

thrombosis Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thr ...

episodes. Treatment of these disorders generally involves specialized centers and the establishment of preventive measures designed based on each individuals personal and family histories of the frequency and severity of previous bleeding and thrombosis episodes, and, in a select few cases, the predicted propensity of the genetic mutations which underlie their disorders to cause bleeding and thrombosis.

Signs and symptoms

Afibrinogenemia is typically the most severe of the three disorders. Common symptoms include bleeding of the umbilical cord at birth, traumatic and surgical bleeding, GI tract, oral and mucosal bleeding, spontaneous splenic rupture, and rarely intracranial hemorrhage and articular bleeding. Symptoms of hypofibrinogenemia varies from mild to severe, but can include bleeding of the GI tract, oral and mucosal bleeding, and very rarely intracranial bleeding. More commonly it presents during traumatic bleeding or surgical procedures. Most cases (60%) of dysfibrinogenemia are asymptomatic, but 28% exhibit hemorrhaging similar to that described above while 20% exhibit thrombosis (i.e. excessive clotting).

Causes

The disorders associated with Factor I deficiency are generally inherited, although certain liver diseases can also affect fibrinogen levels and function (e.g.

cirrhosis Cirrhosis, also known as liver cirrhosis or hepatic cirrhosis, and end-stage liver disease, is the impaired liver function caused by the formation of scar tissue known as fibrosis due to damage caused by liver disease. Damage causes tissue repai ...

). Afibrinogenemia is a recessive inherited disorder, where both parents must be carriers. Hypofibrinogenemia and dysfibrinogenemia can be dominant (i.e. only one parent needs to be a carrier) or recessive. The origin of the disorders is traced back to three possible genes: FGA, FGB, or FGG. Because all three are involved in forming the hexameric glycoprotein fibrinogen, mutations in any one of the three genes can cause the deficiency.

Diagnosis

Treatment

The most common type of treatment is

cryoprecipitate Cryoprecipitate, also called cryo for short, is a frozen blood product prepared from blood plasma. To create cryoprecipitate, fresh frozen plasma thawed to 1–6 °C is then centrifuged and the precipitate is collected. The precipitate is re ...

or fibrinogen concentrate drip to increase fibrinogen levels to normal during surgical procedures or after trauma. RiaSTAP, a factor I concentrate, was approved by the U.S. FDA in 2009 for use when the fibrinogen level was below 50 mg/deciliter of plasma. Recently,

antifibrinolytic Antifibrinolytics are a class of medication that are inhibitors of fibrinolysis. Examples include aminocaproic acid (ε-aminocaproic acid) and tranexamic acid. These lysine Lysine (symbol Lys or K) is an α-amino acid that is a precursor t ...

s have also been used to inhibit

fibrinolysis Fibrinolysis is a process that prevents blood clots from growing and becoming problematic. Primary fibrinolysis is a normal body process, while secondary fibrinolysis is the breakdown of clots due to a medicine, a medical disorder, or some other c ...

(breaking down of the fibrin clot). In the case of dysfibrinogenemia that manifests by

, anticoagulants can be used. Due to the inhibited clotting ability associated with a- and hypofibrinogenemia, physicians advise against the use of

Aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat in ...

as it inhibits platelet function.

References

External links