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Hemophilia for PA

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Hemophilia for the Physician Assistant Licensing Exam
  • Definition:
    • Hemophilia is an X-linked recessive bleeding disorder caused by deficiencies in specific clotting factors, leading to prolonged bleeding and impaired clot formation.
    • Primarily affects males, as the defective gene is located on the X chromosome, though some female carriers may have mild symptoms.
  • Types:
    • Hemophilia A: Factor VIII deficiency, more common, comprising ~80% of cases.
    • Hemophilia B (Christmas Disease): Factor IX deficiency, accounting for ~20% of cases.
Pathophysiology and Severity
  • Factor Deficiency:
    • Factor VIII and factor IX are intrinsic pathway proteins essential for the activation of factor X and stable clot formation.
    • Deficiencies result in delayed thrombin formation, leading to prolonged bleeding.
Hemophilia pathophysiology
  • Severity:
    • Severe: Factor activity <1% of normal, with spontaneous bleeding.
    • Moderate: Factor activity 1–5%, with bleeding after mild trauma.
    • Mild: Factor activity 5–40%, with bleeding only after significant trauma or surgery.
Clinical Presentation
  • Bleeding Sites:
    • Hemarthrosis: Recurrent bleeding in joints (knees, elbows, ankles), leading to joint damage if untreated.
    • Muscle Bleeding: Deep muscle bleeding, particularly in the thigh or iliopsoas.
    • Mucocutaneous Bleeding: Uncommon but may occur with minor injuries.
    • Intracranial Hemorrhage: Life-threatening and often trauma-induced.
  • Post-Traumatic Bleeding:
    • Prolonged bleeding after minor surgeries or injuries, especially in mild or moderate hemophilia.
Diagnosis
  • Laboratory Findings:
    • Prothrombin Time (PT): Normal.
    • Activated Partial Thromboplastin Time (aPTT): Prolonged due to intrinsic pathway defect.
    • Factor Assays: Low levels of factor VIII (hemophilia A) or factor IX (hemophilia B) confirm the diagnosis.
Treatment
  • Factor Replacement Therapy:
    • On-Demand: For active bleeding.
    • Prophylactic: Regular infusions in severe cases to prevent spontaneous bleeding.
    • Bypassing Agents: Recombinant factor VIIa or activated prothrombin complex concentrate (aPCC) for patients with inhibitors.
  • Emicizumab:
    • A bispecific antibody used for prophylaxis in hemophilia A, effective even in patients with inhibitors.
  • Adjunctive Therapies:
    • Antifibrinolytics: Tranexamic acid for mucosal bleeding or dental procedures.
    • Pain Management: Acetaminophen preferred to avoid platelet inhibition by NSAIDs.
Key Points
  • Hemophilia is an X-linked recessive disorder due to factor VIII or IX deficiency, primarily affecting males.
  • Severity depends on factor levels, with spontaneous bleeding in severe cases.
  • Diagnosis involves prolonged aPTT and specific factor assays.
  • Management includes factor replacement, emicizumab for hemophilia A, and antifibrinolytics for mucosal bleeding.

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