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FGA gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

FGA gene

The FGA gene provides instructions for the fibrinogen A alpha chain, a critical protein subunit required for blood clot formation.

Normal Function

The FGA gene provides instructions for making a protein called the fibrinogen A alpha (Aα) chain, one subunit of the fibrinogen protein. This protein is important for blood clot formation (coagulation), which is needed to stop excessive bleeding after injury. To form fibrinogen, the Aα chain attaches to two other proteins called the fibrinogen B beta (Bβ) and fibrinogen gamma (γ) chains. Two sets of this three-protein complex combine to form functional fibrinogen.

For coagulation to occur, another protein called thrombin removes a piece from the Aα and Bβ subunits. This process converts fibrinogen to fibrin, the main protein in blood clots. Fibrin proteins attach to each other, forming a stable network that makes up the blood clot.

Health Conditions Related to Genetic Changes

Congenital afibrinogenemia

Mutations in the FGA gene can lead to congenital afibrinogenemia, a condition that causes excessive bleeding due to the absence of fibrinogen protein in the blood. If any fibrinogen Aα chain is produced, it is nonfunctional. Because this condition occurs when both copies of the FGA gene are altered, there is a complete absence of functional fibrinogen Aα chain, preventing the assembly of fibrinogen and the formation of blood clots.

Other disorders

  • Hypofibrinogenemia: Characterized by decreased levels of fibrinogen in the blood, caused by mutations that reduce but do not eliminate the production of the fibrinogen Aα chain.
  • Dysfibrinogenemia: Characterized by abnormally functioning fibrinogen present at normal levels, usually caused by mutations that change a single amino acid. This can lead to excessive bleeding or abnormal blood clotting (thrombosis).
  • Hypodysfibrinogenemia: Characterized by low levels of abnormally functioning fibrinogen protein in the blood.
  • Hereditary renal amyloidosis: Caused by FGA mutations that lead to the accumulation of abnormal fibrinogen Aα chain proteins in the kidneys (amyloid deposits), resulting in kidney impairment and potential failure.

Other Names for This Gene

  • Fib2
  • FIBA_HUMAN
  • fibrinogen alpha chain isoform alpha preproprotein
  • fibrinogen alpha chain isoform alpha-E preproprotein
  • fibrinogen, A alpha polypeptide

Frequently Asked Questions

Both conditions show low or abnormal fibrinogen activity, but hypofibrinogenemia presents with reduced fibrinogen antigen levels and functional activity. Dysfibrinogenemia typically has normal antigen levels but abnormal clotting function; a functional fibrinogen assay (e.g., clotting time) will be prolonged while antigen measurement remains normal. A fibrinogen functional assay combined with antigen quantification is the standard approach.
Patients with congenital afibrinogenemia often experience spontaneous bruising, prolonged bleeding after minor cuts, heavy menstrual bleeding, and excessive bleeding during surgery or dental procedures. Symptoms can appear at birth or in early infancy, but some individuals may not notice significant bleeding until later childhood or adolescence when they undergo more invasive procedures.
Management depends on the clinical presentation. For bleeding episodes, fibrinogen concentrates or cryoprecipitate can be administered to raise fibrinogen levels. For patients with a tendency toward thrombosis, low‑dose anticoagulation (e.g., aspirin or low‑molecular‑weight heparin) may be considered after careful risk assessment. Regular monitoring of fibrinogen levels and coagulation parameters guides therapy.
Certain factors can affect fibrinogen levels. Inflammation, infection, and liver disease can raise fibrinogen, while pregnancy and estrogen therapy may also increase levels. Conversely, smoking and some medications (e.g., anticoagulants) can lower fibrinogen activity. Patients should discuss medication use with their clinician and maintain a healthy diet, regular exercise, and avoid smoking to help stabilize clotting factors.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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