ISSN 2398-2969      

Immune-mediated thrombocytopenia

icanis

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


Introduction

  • Most common acquired primary hemostatic defect in dogs.
  • Cause: characterized by immune-mediated 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, immunosuppressive therapy. Platelet transfusions can provide transient improvement, but do not substantially increase platelet counts and as such, are reserved for life threatening hemorrhage.
  • 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

Secondary causes

  • Inflammatory and infectious disorders, eg Ehrlichia, Anaplasma platys, Babesia, Leishmania, Leptospirosis, Angiostrongylus vasorum.
  • Other immune-mediated diseases, eg immune-mediated hemolytic anemia Anemia: immune mediated hemolytic.
  • Neoplasia especially hematopoietic neoplasia and lymphoma.
  • Following medication with:
    • Sulfonamides.
    • Cephalosporins.
    • Penicillins.
    • Phenylbutazone.
    • Aspirin.
    • Gold salts.
    • Estrogens.
    • Possible response following live-virus vaccination.

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 megakaryocytes impairing production.
  • Bleeding only occurs when platelet count is markedly reduced (<50 x 109/l).
  • Thrombocytopenia -> defective primary hemostasis leading to petechial and ecchymotic hemorrhage.
  • Secondary hemostasis is unaffected.

Timecourse

  • Development of thrombocytopenia is usually acute or sub-acute.
  • Clinical signs invariably acute once severe thrombocytopenia has 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.
  • LaQuaglia K A, Robertson J B, Lunn K F (2021) Neutropenia in dogs receiving vincristine for treatment of presumptive immune-mediated thrombocytopenia.J Vet Intern Med 35, 226- 233 PubMed.  
  • Simpson K, Chapman P & Klag A (2018) Long-term outcome of primary immune-mediated thrombocytopenia in dogs. J Small Anim Pract 59, 674-680 PubMed
  • Cummings F O & Rizzo S A (2017) Treatment of presumptive primary immune-mediated thrombocytopenia with mycophenolate mofetil versus cyclosporine in dogs. J Small Anim Pract 58, 96-102 PubMed.
  • Kohn B, Bal G, Chirek A, Rehbein S, Salama A (2016) Treatment of 5 dogs with immune-mediated thrombocytopenia using Romiplostim. BMC Vet Res 12, 96 PubMed (Erratum in: BMC Vet Res 12 (1), 290 PMID: 27283401; PMCID: PMC4901510). 
  • Huang A, Moore G & Scott-Moncrieff J (2012) Idiopathic Immune-Mediated Thrombocytopenia and Recent Vaccination in Dogs. J Vet Intern Med 26, 142-148 PubMed.
  • O'Marra S K, Delaforcade A M, & Shaw S P (2011) Treatment and predictors of outcome in dogs with immune-mediated thrombocytopenia. JAVMA238(3), 346-352 PubMed.   
  • 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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