Canis ISSN: 2398-2942

Immune-mediated thrombocytopenia

Synonym(s): IMT, idiopathic thrombocytopenic purpura, ITP

Contributor(s): Prof Bernard Feldman

Introduction

  • Most common cause of acquired defective hemostasis in dog.
  • Cause: characterized by increased destruction of antibody coated platelets.
  • Most often occurs as primary autoimmune disease but may occur secondary to infections, neoplasia or as an adverse reaction to medication.
  • Treatment: glucocorticoids, platelet transfusion, is most difficult due to logistics and potential immune reaction, immunosuppressive therapy.
  • Prognosis: good, rarely fatal.
    Print off the owner factsheet on Immune-mediated thrombocytopenia Immune-mediated thrombocytopenia to give to your client.

Pathogenesis

Etiology

  • Most often occurs as a primary auto-immune disease.
  • Antibody-mediated platelet destruction may occur secondary to other disease processes or as a side-effect of medication.

Predisposing factors

General

  • Following medication with:
    • Sulfonamides.
    • Cephalosporins.
    • Penicillins.
    • Phenylbutazone.
    • Aspirin.
    • Gold salts.
    • Estrogens.
    • Possible response following live-virus vaccination.
  • Angiostrongylus vasorum infection Angiostrongylus vasorum.

Pathophysiology

  • Accelerated destruction of antibody coated platelets → decreased circulating platelet lifespan.
  • Thrombocytopenia develops when destruction is greater than production.
  • Platelet production in bone marrow normally stimulated though in some cases anti-platelet antibodies cross react with megakaryocyes impairing production.
  • Bleeding only occurs when platelet count is markedly reduced (<50 x 10*9/l).
  • Thrombocytopenia -> defective primary hemostasis leading to petechial and ecchymotic hemorrhage.
  • Secondary hemostasis remains intact.

Timecourse

  • Development of thrombocytopenia is usually acute or sub-acute.
  • Clinical signs invariably acute once thrombocytopenia developed.

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.
  • Botsch V et al (2009) Retrospective study of 871 dogs with thrombocytopenia. Vet Rec 164 (21), 647-651 PubMed.
  • Gould S M & McInnes E L (1999) Immune-mediated thrombocytopenia associated with Angiostrongylus vasorum infection in a dog. JSAP 40 (5), 227-232 PubMed.


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