Fibrinogen
๐งฌ Fibrinogen has two main roles: (1) as the substrate for fibrin formation and (2) as a ligand for the platelet ฮฑIIฮฒIII receptor, promoting platelet aggregation.
๐ About
- Fibrinogen (Factor I): ๐ฉธ A clotting factor found in high concentrations in plasma, playing a crucial role in blood clot stabilization and haemostasis.
- ๐ Converted to fibrin by thrombin, forming a stable blood clot and helping to stop bleeding.
- ๐ก๏ธ Beyond haemostasis, fibrinogen is involved in thrombosis, host defense, inflammation, and wound healing processes.
๐งฌ Aetiology
- Genetic Encoding: Fibrinogen is encoded by three genes located on chromosome 4:
- ๐งพ Aฮฑ (FGA)
- ๐งพ Bฮฒ (FGB)
- ๐งพ ฮณ (FGG)
- ๐ญ A glycoprotein produced primarily by the liver and secreted into the bloodstream both basally and in response to stimuli.
- ๐ค Supports platelet aggregation by binding to the platelet ฮฑIIฮฒIII receptor.
โ ๏ธ Clinical Significance
- โฌ๏ธ Low fibrinogen levels โ increased risk of bleeding and impaired clot formation.
- โฌ๏ธ Elevated fibrinogen levels โ contribute to thrombosis, as fibrinogen is an acute phase reactant and may rise during inflammation, infection, or tissue injury.
๐ Investigations
- ๐ Normal Range: Plasma fibrinogen levels are typically between 2โ4 g/L.
- โฌ๏ธ Elevated Fibrinogen: Acute phase reactant, rising in inflammation, infection, or trauma.
- โฌ๏ธ Decreased Fibrinogen: Causes include:
- ๐ฉธ Haemorrhage
- ๐ง Haemodilution (e.g., excessive IV fluids)
- ๐ฆ Sepsis
- โก Consumption in DIC (Disseminated Intravascular Coagulation) or thrombosis
- ๐งฌ Congenital disorders:
- Afibrinogenaemia: โ Complete absence of fibrinogen โ severe bleeding.
- Hypofibrinogenaemia: โฌ๏ธ Reduced levels โ mild to severe bleeding.
- Dysfibrinogenaemia: โ ๏ธ Normal levels but dysfunctional fibrinogen โ abnormal clotting.
๐งซ Pathology
- โฌ๏ธ Fibrinogen Deficiency: โ uncontrolled bleeding, haemorrhagic complications.
- โฌ๏ธ Thrombosis Risk: โ elevated fibrinogen may indicate inflammation or hypercoagulability.
๐ Management
- Replacement Therapy: ๐งช via fresh frozen plasma (FFP) or cryoprecipitate (usually 10 units).
- ๐ฏ Target Levels: โฅ 1 g/L in bleeding patients.
- Fibrinogen Concentrate: ๐ Available as a medication โ consult the BNF for guidelines.
๐ References
