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Immune-mediated thrombocytopenia

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Synonym(s): IMTP


Introduction

  • Immune-mediated thrombocytopenia (IMTP) is rare and poorly documented in the cat (in contrast to the dog).
  • Cause: most cases are likely to be secondary (particularly to FeLV infection and associated neoplasia) rather than primary autoimmune thrombocytopenia (AITP).
  • Signs: vague, eg anorexia, lethargy.
  • Diagnosis: often presumptive, platelet count <50,000, anti-platelet antibody.
  • Treatment: treat underlying condition and immunosuppression if required.
  • Prognosis: guarded.
    Print off the owner factsheet on Immune-mediated thrombocytopenia  Immune-mediated thrombocytopaenia to give to your client.

Pathogenesis

Predisposing factors

General

  • Underlying disease.

Specific

Pathophysiology

  • Antibody binds to platelets   →   early removal from circulation   →   clinical signs.
  • Antibody (IgG or IgM) and/or complement bound to platelet membrane. Antibody-labeled cells are removed by phagocytic cells in spleen (Type II hypersensitivity) in excess of replacement by bone marrow thrombopoiesis.
  • Antibody may also inhibit platelet function (dog; not documented in cat).
  • Antibody may be specific for platelet membrane antigens, or for adsorbed drug or infectious agent, or membrane antigens modified or exposed by binding of such agents.
  • Antibody may be specific for bone marrow precursors (megakaryocytes) leading to immune-mediated amegakaryocytic thrombocytopenia.
  • May be concurrent immune-mediated hemolytic anemia Anemia: immune-mediated hemolytic  , or IMTP may be part of multisystemic immune-mediated disease (systemic lupus erythematosus  Systemic lupus erythematosus).

Timecourse

  • Months.

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.
  • Garon C L, Scott M A, Selting K A et al (1999) Idiopathic thrombocytopenic purpura in a cat. JAAHA 35 (6), 464-470 PubMed.
  • Tasker S, Mackin A J & Day M J (1999) Primary immune-mediated thrombocytopenia in a cat. JSAP 40 (3), 127-131 PubMed.
  • Jordan H L, Grindem C B & Breitschwerdt E B (1993) Thrombocytopenia in cats- a retrospective study of 41 cases. JVIM (5), 261-265 PubMed.
  • Gaschen F P, Smith Meyer B and Harvey J W (1992) Amegakarocytic thrombocytopenia and immune-mediated haemolytic anaemia in a cat. Comparative Haematology International (3), 175-8 VetMedResource.

Other sources of information

  • Day M J (1999) Clinical immunology of the dog and cat. London: Manson Publishing. ISBN:1 8745 4598 7.
  • Smith J et al (1999) Chronic thrombocytopenia and epistaxis in a cat. Feline Practice 27 (3), 5-8.

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