Immune-Mediated Thrombocytopenia

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Thank you to Patti Emmett, MS, RN, CIC for putting together and updating this article for SCARF.

Immune-Mediated Thrombocytopenia is a decreased numbers of blood platelets due to platelet destruction by the immune system.

Signs and Symptoms

Spontaneous visible bruising is the major clinical sign. Small spidery spots of bruising clustered together are called “petechiae”. Petechiae are the most common sign. Larger purple areas of bruising are called “ecchymosis”.


In many cases, a cause isn’t found. In some cases, a primary reaction by the immune system precedes the act of platelet destruction.

Examples of reactions in the immune system that could be followed by platelet destruction include:

  • a parasitic infection of blood (Ehrlichiosis, Rocky Mountain Spotted Fever)
  • a tumor
  • drugs (chemotherapy agents, sulfonamide and chloramphenicol antibiotics)
  • Lupus

Risk Factors

  • exposure to ticks and tick-borne blood parasites
  • pre-existing Lupus
  • a diagnosis of bone marrow cancer
  • certain treatments for cancer and infections

Diagnostic Tests

Inspection of gums and mouth, whites of the eyes, and abdomen may reveal petechiae or ecchymosis. Blood platelet counts can determine if numbers of platelets are normal or too low, or appear abnormal. Veterinarian diagnosis on a case-by-case basis, using tests for other diseases combined with symptom assessment. A test is not yet commercially available in the United States to detect anti-platelet antibodies in dogs. A test is available for humans, and for dogs in the UK.

Treatment Guidelines

Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.

  • Treatment of the cause, if known

  • Prednisone or dexamethasone immunosuppression

  • Azathioprine if no response to above

  • Transfusion when a crisis occurs

  • Splenectomy

    Plasma exchange has been cited as an emerging treatment. Improvement of hemorrhages occurred in a small number of dogs in a research report.


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