Canis ISSN: 2398-2942

Thrombocytopenia

Introduction

  • Thrombocytopenia is a clinical sign and NOT a diagnosis - investigation is directed at identifying underlying cause.
  • Cause: decreased production or increased utilization of platelets.
  • Signs: may be no clinical signs or signs of bleeding.
  • Diagnosis: hematology.
  • Treatment: depends on cause.
  • Prognosis: depends on cause.
    Print off the owner factsheet on Thrombocytopenia (decreased platelet count) Thrombocytopenia (decreased platelet count) to give to your client.

Pathogenesis

Etiology

Decreased platelet production

  • Aplastic anemia - many possible causes including estrogens (thrombocytosis initially), phenylbutazone Phenylbutazone , thiazide diuretics, toxins, and chemotherapeutic drugs.
  • Myeloproliferative and lymphoproliferative disorders Myeloproliferative tumor Lymphoproliferative disease.
  • Myelophthisic disease.
  • 'Rebound' thrombocytopenia (following blood transfusion Blood: transfusion ).
  • Megakaryocyte destruction in marrow:
    • Immune mediated.

Increased platelet destruction

Increased platelet utilization

  • Disseminated intravascular coagulopathy (DIC) Disseminated intravascular coagulation.
  • Severe hemorrhage (theoretical cause of thrombocytopenia unlikely in practice).
    In about 20% cases no underlying pathology is identified.

Predisposing factors

General

Pathophysiology

  • Platelets produced by megakaryocytes in the marrow.
  • Megakaryopoiesis takes 4 weeks and circulating platelets have a lifespan of 1 week under normal circumstances.
  • Suppression of platelet precursors in marrow → drop in number of platelets released to circulation.
  • Short lifespan of platelets means that thrombocytopenia may be seen before other cytopenias in marrow disease.
  • In DIC generalized intravascular coagulation consumes platelets.
  • Immune mediated destruction of platelets can be primary or secondary:
    • Primary → production of antibodies against platelets.
    • Secondary → platelets destroyed due to cross reaction of antibodies against other things, eg drugs.
  • Low platelet counts may cause spontaneous bleeding.

Timecourse

  • May be chronic before clinical signs recognized.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Botsch Vet al (2009) Retrospective study of 871 dogs with thrombocytopenia. Vet Rec 164 (12), 647-651 PubMed.


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