Bleeding Disorders

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Hemostasis Essentials - Clotting Cascade Crew

Normal hemostasis:

  1. Vascular Spasm: Rapid vessel constriction, limits initial blood loss.
  2. Platelet Plug: Platelets adhere, activate, aggregate (Primary Hemostasis).
  3. Coagulation Cascade: Sequential factor activation for fibrin clot (Secondary Hemostasis).
    • Intrinsic: Contact activation (collagen). Factors: XII, XI, IX, VIII. (Monitored by aPTT).
    • Extrinsic: Tissue Factor (TF III) release. Factor: VII. (Monitored by PT/INR).
    • Common: Convergence of pathways. Factors: X, V, II (Prothrombin), I (Fibrinogen), XIII (stabilizes clot).
  4. Fibrinolysis: Plasmin-mediated breakdown of fibrin, restoring blood flow.

Coagulation Cascade Pathways

⭐ Vitamin K dependent factors are II, VII, IX, X, Protein C & S. (Mnemonic: 1972, C, S) 📌

Platelet Problems - Plug Pullers' Plight

  • Thrombocytopenia (↓ Platelets):
    • ITP (Immune Thrombocytopenic Purpura): Autoantibodies vs GpIIb/IIIa. 📌 ITP: Idiots Trashing Platelets. Bleeding if < 10,000-20,000/μL.
    • TTP (Thrombotic Thrombocytopenic Purpura): ADAMTS13 deficiency (vWF cleaving protease).

      ⭐ TTP pentad: Fever, Anemia (microangiopathic hemolytic), Thrombocytopenia, Renal failure, Neurological symptoms (FAT RN).

    • HUS (Hemolytic Uremic Syndrome): E. coli O157:H7 (Shiga toxin). Triad: MAHA, thrombocytopenia, ARF.
    • DIC (Disseminated Intravascular Coagulation): Widespread clotting activation → consumption → bleeding. ↑PT/PTT/D-dimer, ↓Fibrinogen.
  • Qualitative Platelet Defects:
    • Bernard-Soulier Syndrome: GpIb defect. Impaired adhesion to vWF. Large platelets.
    • Glanzmann Thrombasthenia: GpIIb/IIIa defect. Impaired aggregation.
  • Von Willebrand Disease (vWD): Commonest inherited bleeding disorder; vWF defect. Mucocutaneous bleeding.
    • Types: 1 (partial quantitative ↓), 2 (qualitative defect), 3 (severe/total quantitative ↓).
    • Dx: ↓vWF:Ag, ↓Ristocetin cofactor activity, PTT may be ↑ (due to ↓FVIII). Peripheral blood smear: TTP with schistocytes

Coagulation Chaos - Factor Fumbles

  • Hemophilias: Inherited X-linked (A & B) or Autosomal (C) bleeding disorders due to specific factor deficiencies.
    FeatureHemophilia A (Classic)Hemophilia B (Christmas Dis.) 📌Hemophilia C
    DeficiencyFactor VIIIFactor IXFactor XI
    InheritanceX-linked recessiveX-linked recessiveAutosomal Rec.
    Labs (PT/PTT/BT)N PT, ↑PTT, N BTN PT, ↑PTT, N BTN PT, ↑PTT, N BT
    Severity (F.VIII/IX)<1% severe, 1-5% mod., >5-40% mild<1% severe, 1-5% mod., >5-40% mildVariable bleeding
  • Vitamin K Deficiency:
    • ↓ Factors II, VII, IX, X, Protein C & S (📌 2,7,9,10,C,S).
    • ↑PT (earliest), then ↑PTT. Normal BT.
    • Causes: Neonates, malabsorption, broad-spectrum antibiotics, warfarin.
  • Liver Disease Coagulopathy:
    • ↓ Synthesis of most clotting factors (except FVIII, vWF) & anticoagulants.
    • ↑PT, ↑PTT. Dysfibrinogenemia. ↓Platelets (hypersplenism).
  • Disseminated Intravascular Coagulation (DIC): Pathological systemic activation of coagulation. Widespread microthrombi consume platelets & factors, leading to bleeding.
    • Labs: ↑PT, ↑PTT, ↑BT, ↓Fibrinogen, ↑D-dimer (key), ↓Platelets, Schistocytes.
  • Anticoagulant Effects:
    • Heparin: Potentiates Antithrombin III; ↑PTT.
    • Warfarin: Inhibits Vit K epoxide reductase; ↑PT/INR.

⭐ Mixing studies differentiate factor deficiency (correction with normal plasma) from an inhibitor (no correction).

Lab Lowdown - Bleed Sleuth

Key tests: Platelet Count (Plt Ct), BT/PFA-100, PT, aPTT. D-dimer for DIC. Fibrinogen levels. Thrombin Time (TT).

Lab Patterns:

DisorderPlt CtBT/PFAPTaPTTKey
ITP↓↓↓NNIsolated thrombocytopenia
Hemophilia A/BNNNFactor VIII/IX deficiency
vWD (common)NNN/↑Most common inherited
DIC (acute)↑D-dimer, ↓Fibrinogen, ↑TT
Vit K DefNNN/↑Early: ↑PT; Severe: ↑PT & ↑aPTT

High‑Yield Points - ⚡ Biggest Takeaways

  • Hemophilia A (FVIII↓) & B (FIX↓): X-linked, ↑aPTT, normal PT/BT.
  • Von Willebrand Disease (vWD): Most common inherited, ↑BT, often ↑aPTT (vWF stabilizes FVIII).
  • ITP: Isolated thrombocytopenia (anti-GpIIb/IIIa Abs), ↑BT, normal PT/aPTT.
  • DIC: Widespread clotting activation, ↑PT/aPTT/BT/D-dimer, ↓platelets, schistocytes.
  • Vitamin K Deficiency: Affects II, VII, IX, X, C, S; ↑PT (early), then ↑aPTT.
  • TTP: ADAMTS13 deficiency; Pentad: Fever, MAHA, Thrombocytopenia, Renal, Neurologic.

Practice Questions: Bleeding Disorders

Test your understanding with these related questions

Disseminated intravascular coagulation (DIC) differs from thrombotic thrombocytopenic purpura. In this reference, DIC is most likely characterized by:

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Flashcards: Bleeding Disorders

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Hemophilia _____ is a coagulation disorder due to a genetic factor XI deficiency

TAP TO REVEAL ANSWER

Hemophilia _____ is a coagulation disorder due to a genetic factor XI deficiency

C

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