Encyclopedia
Congenital afibrinogenemia is a bleeding disorder caused by impairment of the blood clotting process.
- genetic conditions
1. Introduction
Normally, blood clots protect the body after an injury by sealing off damaged blood vessels and preventing further blood loss. However, bleeding is uncontrolled in people with congenital afibrinogenemia. Newborns with this condition often experience prolonged bleeding from the umbilical cord stump after birth. Nosebleeds (epistaxis) and bleeding from the gums or tongue are common and can occur after minor trauma or in the absence of injury (spontaneous bleeding). Some affected individuals experience bleeding into the spaces between joints (hemarthrosis) or the muscles (hematoma). Rarely, bleeding in the brain or other internal organs occurs, which can be fatal. Women with congenital afibrinogenemia can have abnormally heavy menstrual bleeding (menorrhagia). Without proper treatment, women with this disorder may have difficulty carrying a pregnancy to term, resulting in repeated miscarriages.
2. Frequency
Congenital afibrinogenemia is a rare condition that occurs in approximately 1 in 1 million newborns.
3. Causes
Congenital afibrinogenemia results from mutations in one of three genes, FGA, FGB, or FGG. Each of these genes provides instructions for making one part (subunit) of a protein called fibrinogen. This protein is important for blood clot formation (coagulation), which is needed to stop excessive bleeding after injury. In response to injury, fibrinogen is converted to fibrin, the main protein in blood clots. Fibrin proteins attach to each other, forming a stable network that makes up the blood clot.
Congenital afibrinogenemia is caused by a complete absence of fibrinogen protein. Most FGA, FGB, and FGG gene mutations that cause this condition result in a premature stop signal in the instructions for making the respective protein. If any protein is made, it is nonfunctional. When any one subunit is missing, the fibrinogen protein is not assembled, which results in the absence of fibrin. Consequently, blood clots do not form in response to injury, leading to the excessive bleeding seen in people with congenital afibrinogenemia.
4. Inheritance
Congenital afibrinogenemia is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene. The parents have about half the normal level of fibrinogen in their blood but typically do not show signs and symptoms of the condition.
5. Other Names for This Condition
- afibrinogenemia
- familial afibrinogenemia
This entry is adapted from the peer-reviewed paper https://medlineplus.gov/genetics/condition/congenital-afibrinogenemia
References
- Casini A, Lukowski S, Quintard VL, Crutu A, Zak M, Regazzoni S, de MoerlooseP, Neerman-Arbez M. FGB mutations leading to congenital quantitative fibrinogendeficiencies: an update and report of four novel mutations. Thromb Res. 2014May;133(5):868-74. doi: 10.1016/j.thromres.2014.01.022.
- de Moerloose P, Casini A, Neerman-Arbez M. Congenital fibrinogen disorders: anupdate. Semin Thromb Hemost. 2013 Sep;39(6):585-95. doi: 10.1055/s-0033-1349222.
- Lak M, Keihani M, Elahi F, Peyvandi F, Mannucci PM. Bleeding and thrombosis in55 patients with inherited afibrinogenaemia. Br J Haematol. 1999Oct;107(1):204-6.
- Neerman-Arbez M, de Moerloose P, Bridel C, Honsberger A, Schönbörner A,Rossier C, Peerlinck K, Claeyssens S, Di Michele D, d'Oiron R, Dreyfus M,Laubriat-Bianchin M, Dieval J, Antonarakis SE, Morris MA. Mutations in thefibrinogen aalpha gene account for the majority of cases of congenitalafibrinogenemia. Blood. 2000 Jul 1;96(1):149-52.
- Neerman-Arbez M, de Moerloose P, Honsberger A, Parlier G, Arnuti B, Biron C,Borg JY, Eber S, Meili E, Peter-Salonen K, Ripoll L, Vervel C, d'Oiron R, StaegerP, Antonarakis SE, Morris MA. Molecular analysis of the fibrinogen gene clusterin 16 patients with congenital afibrinogenemia: novel truncating mutations in theFGA and FGG genes. Hum Genet. 2001 Mar;108(3):237-40.
- Neerman-Arbez M, Honsberger A, Antonarakis SE, Morris MA. Deletion of thefibrinogen [correction of fibrogen] alpha-chain gene (FGA) causes congenitalafibrogenemia. J Clin Invest. 1999 Jan;103(2):215-8. Erratum in: J Clin Invest1999 Mar;103(5):759.
- Neerman-Arbez M. Molecular basis of fibrinogen deficiency. PathophysiolHaemost Thromb. 2006;35(1-2):187-98. Review.
- Weisel JW. Fibrinogen and fibrin. Adv Protein Chem. 2005;70:247-99. Review.
