ISSN 2398-2950      

Thrombocytopenia

ffelis

Introduction

  • Thrombocytopenia is apparently rare in the cat (incidence 5.9%) - but may be under-diagnosed.
  • It 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 Thrombocytopenia (decreased platelet count) to give to your client.

Pathogenesis

Etiology

Decreased platelet production

Increased platelet destruction

  • Immune mediated destruction Immune-mediated thrombocytopenia:
    • Primary (rare in the cat).
    • Secondary (to concurrent infection or neoplasia).
    • Immune mediated causes are less common in cats than in dogs; only 11% of cats in one study were diagnosed with immune mediated disease.

Increased platelet utilization

  • Disseminated intravascular coagulopathy Disseminated intravascular coagulation.
  • Severe hemorrhage (theoretical cause of thrombocytopenia unlikely in practice).
    In about 42% cases no underlying pathology is identified.

Predisposing factors

General

Pathophysiology

  • Low platelet counts may cause spontaneous bleeding.
  • < 30% cats showed spontaneously bleeding with thrombocytopenia.
  • 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 Disseminated intravascular coagulation.
  • 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.

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.
  • Ellis J, Bell R, Barnes D C, Miller R (2018) Prevalence and disease associations in feline thrombocytopenia: a retrospective study of 194 cases. JSAP 59(9), 531-538 PubMed.
  • Savidge C, Ewing P, Andrews J, Aucoin D, Lappin M R, Moroff S (2016) Anaplasma phagocytophilum infection of domestic cats: 16 cases from the northeastern USA. J Feline Med Surg 18(2), 85-91 PubMed.
  • Nagel S S, Williams J H & Schoeman J P (2013) Fatal disseminated toxoplasmosis in an immunocompetent cat.J S Afr Vet Assoc  84(1), 1-6 PubMed.
  • Wondratschek C, Weingart C & Kohn B (2010) Primary Immune-Mediated Thrombocytopenia in Cats. JAAHA 46,12-19 PubMed.
  • Hartmann K (2005) Feline infectious peritonitis. Vet Clin North Am Small Anim Pract 35(1), 39-79 PubMed.
  • Tasker S, Cripps P J & Mackin A J (2001) Evaluation of methods of platelet counting in the cat. JSAP 42 (7), 326-332 PubMed.
  • Tasker S, Mackin A J & Day M J (1999) Primary immune-mediated thrombocytopenia in a cat. JSAP 40 (3), 127-131 PubMed.
  • Hodson S & Mackin A (1998) Thrombocytopenia in the cat. Feline Focus 8, 2-7.
  • Boyce J T, Kociba G J, Jacobs R M et al (1986) Feline leukemia induced thrombocytopenia and macrothrombocytosis in cats. Vet Pathol 23 (1), 16-20 PubMed.

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