Canis ISSN: 2398-2942

Hemophilia A

Synonym(s): Factor VIII deficiency

Contributor(s): Prof Bernard Feldman

Introduction

  • Inherited X-linked recessive trait, carried by female - affects male.
  • Occurs in most breeds of dogs, mongrels.
  • Factor VIII is active in intrinsic pathway; together with factor IX and calcium; it activates factor X.
  • Signs: mild-moderate-severe bleeding tendency, commonly seen as hematomata on body surface or hemarthrosis.
  • Prognosis: prolonged bleeding after surgery or trauma, may be fatal.

Pathogenesis

Etiology

  • Genetic inherited disease X-linked recessive trait.
  • Carried by heterozygous females; affects males and homozygous females (rare).

Specific

  • Disease may manifest following vaccination with live vaccines which cause a temporary reduction in number and function of platelets.

Pathophysiology

  • Factor VIII is active in intrinsic coagulation system. Together with factor IX and calcium it forms complex which activates factor X (factor X is first coagulation factor in common pathway).
  • Factor VIII, partial or absolute, deficiency → mild - severe hemophilia.
  • Hematoma formation and hemarthrosis → lameness, excessive bruising following trauma or prolonged bleeding after surgery, cuts, wounds.
  • Factor VIII produced by vasular endothelial cells + megakaryocytes. Other clotting factors produced by liver.
  • Deficiency of factor VIII → prolonged intrinsic coagulation cascade → (ultimately) decreased conversion fibrinogen to fibrin → failure of platelet plug to stabilize at sites of vascular injury.
  • Platelets function normally → small endothelial injury sealed by primary platelet plug → no petechial/ecchymotic hemorrhages.
  • Larger vessel injuries → platelet plug not stabilized adequately by coagulation cascade → washed away → large bleeds (hematomata, hemarthrosis, bleeding at surgery).

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Fogh J M & Fogh I T (1988) Inherited coagulation disorders. Vet Clin North Am Small Anim Pract 18 (1), 231-243 PubMed.

Other sources of information

  • Fogh J M (1988)A study of hemophilia A in German Shepherd dogs in Denmark.In:Veterinary Clinics of North America.Feldman B F (ed). Philadelphia: W B Saunders. pp 245-254.
  • Fogh J M & Fogh I T (1988)Inherited Coagulation Disorders.In:Veterinary Clinics of North America.Feldman B F (ed). Philadelphia: W B Saunders. pp 231-244.
  • Johnstone I B (1988)Diagnosis of Bleeding Disorders.In:Veterinary Clinics of North America.Feldman B F (ed). Philadelphia: W B Saunders. pp 21-34.


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