Felis ISSN 2398-2950

Immune-mediated thrombocytopenia

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

• Underlying FeLV infection   Feline leukemia virus disease  .

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

Treatment

Outcomes