Medicine & USMLE

Glanzmann Thrombasthenia

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Platelet Disorders
  1. Platelet Plug Formation
  2. Bernard-Soulier Syndrome
  3. Glanzmann Thrombasthenia
  4. Immune Thrombocytopenic Purpura (ITP)
  5. Thrombotic Thrombocytopenic Purpura (TTP)
  6. Hemolytic Uremic Syndrome (HUS)
  7. Disseminated Intravascular Coagulation (In Progress)
  8. Von Willebrand Disease (In Progress)

Summary

Glanzmann thrombasthenia is an autosomal recessive platelet disorder caused by a defect in Gp2b/3a receptors on the surface of platelets. This causes an impairment in platelet aggregation and blocks the formation of platelet plugs. Clinically, patients with Glanzmann thrombasthenia present with bleeding, such as mucosal bleeding from their gums, nosebleeds, and heavy menses. Laboratory tests reveal a prolonged bleeding time, although platelet counts remain normal.

Key Points

  • Glanzmann Thrombasthenia
    • Pathogenesis
      • Defect in GpIIb/IIIa receptors
        • Also known as integrin αIIbβ3
        • Impairs platelet aggregation via fibrinogen
        • Blocks formation of platelet plug
    • Genetics
      • Autosomal recessive inheritance
    • Presentation
      • Bleeding
        • Mucosal bleeding (e.g. gingival bleeding, epistaxis, menorrhagia)
        • Microhemorrhages (e.g. petechiae, bruising)
    • Diagnosis
      • Increased bleeding time
        • Due to defective primary hemostasis due to impaired platelet aggregation
      • Normal platelet count
      • No platelet clumping seen on peripheral smear
      • Normal ristocetin test
        • Adherence is normal since vWF and GpIb are unaffected
    • Treatment
      • Supportive
        • May require platelet transfusions during surgery or with severe bleeds