Makindo Medical Notes

🧬 Fibrinogen has two main roles: (1) as the substrate for fibrin formation and (2) as a ligand for the platelet αIIβIII receptor, promoting platelet aggregation.

📖 About

• Fibrinogen (Factor I): 🩸 A clotting factor found in high concentrations in plasma, playing a crucial role in blood clot stabilization and haemostasis.
• 🔄 Converted to fibrin by thrombin, forming a stable blood clot and helping to stop bleeding.
• 🌡️ Beyond haemostasis, fibrinogen is involved in thrombosis, host defense, inflammation, and wound healing processes.

🧬 Aetiology

• Genetic Encoding: Fibrinogen is encoded by three genes located on chromosome 4:
  • 🧾 Aα (FGA)
  • 🧾 Bβ (FGB)
  • 🧾 γ (FGG)
• 🏭 A glycoprotein produced primarily by the liver and secreted into the bloodstream both basally and in response to stimuli.
• 🤝 Supports platelet aggregation by binding to the platelet αIIβIII receptor.

⚠️ Clinical Significance

• ⬇️ Low fibrinogen levels → increased risk of bleeding and impaired clot formation.
• ⬆️ Elevated fibrinogen levels → contribute to thrombosis, as fibrinogen is an acute phase reactant and may rise during inflammation, infection, or tissue injury.

🔍 Investigations

• 📊 Normal Range: Plasma fibrinogen levels are typically between 2–4 g/L.
• ⬆️ Elevated Fibrinogen: Acute phase reactant, rising in inflammation, infection, or trauma.
• ⬇️ Decreased Fibrinogen: Causes include:
  • 🩸 Haemorrhage
  • 💧 Haemodilution (e.g., excessive IV fluids)
  • 🦠 Sepsis
  • ⚡ Consumption in DIC (Disseminated Intravascular Coagulation) or thrombosis
  • 🧬 Congenital disorders:
    • Afibrinogenaemia: ❌ Complete absence of fibrinogen → severe bleeding.
    • Hypofibrinogenaemia: ⬇️ Reduced levels → mild to severe bleeding.
    • Dysfibrinogenaemia: ⚠️ Normal levels but dysfunctional fibrinogen → abnormal clotting.

🧫 Pathology

• ⬇️ Fibrinogen Deficiency: → uncontrolled bleeding, haemorrhagic complications.
• ⬆️ Thrombosis Risk: → elevated fibrinogen may indicate inflammation or hypercoagulability.

💊 Management

• Replacement Therapy: 🧪 via fresh frozen plasma (FFP) or cryoprecipitate (usually 10 units).
• 🎯 Target Levels: ≥ 1 g/L in bleeding patients.
• Fibrinogen Concentrate: 💉 Available as a medication – consult the BNF for guidelines.

📚 References

• Wiley Online Library – Fibrinogen