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Autoimmune Thrombocytopenia

General Information

Your pet's natural body defense system is essential for good health. A part of this system produces antibodies that destroy disease-causing organisms. In autoimmune thrombocytopenia, the defense system produces antibodies that attack the animal's own platelets (blood cells necessary for blood clotting). The result is hemorrhage in various parts of the body.

Why these antibodies are formed is not fully understood, but we do know that sometimes the process is triggered by infections or tumors. In other instances, a cause cannot be found.

Important Points in Treatment

1. Autoimmune thrombocytopenia is a life-threatening disease. Hospitalization is often necessary during the early treatment period. Various laboratory tests are needed to monitor the response to treatment.

2. Blood transfusions are necessary in some cases. Some animals require treatment with large doses of very potent drugs. Often there are side effects from the various drugs used to treat this disease. The doctor will describe the normal side effects expected from drug therapy.

3. Give all medication as directed. Call the doctor if you cannot give the medication.

4. Diet: Follow the instructions checked.

____Feed the normal diet.

____A special diet is required. Feed as follows:


5. Water: Follow the instructions checked.

____Keep fresh water available at all times.

____Restrict water intake as follows:


6. Activity: Follow the instructions checked.

____Allow normal activity.

____Restrict activity as follows:

Notify the Doctor if Any of the Following Occur:

* Your pet seems weak or depressed, or refuses to eat.

* Your pet's gums bleed or seem pale.

* Your pet seems short of breath.

* Your pet has blood in the stool or urine.

* Your pet's signs recur after an apparent recovery.

Immune-Mediated Thrombocytopenia (synonyms: immune-mediated thrombopenia, idiopathic thrombocytopenia purpura, ITP)

Etiology
- immune-mediated thrombocytopenia (IMT) occurs when antibodies
bind to the surface of platelets
- this results in premature platelet destruction by macrophages
- IMT may occur alone or in association with:
- systemic lupus erythematosus (SLE)
- rheumatoid arthritis
- neoplasia
- viral, bacterial, rickettsiae, and parasitic infections
- drug administration

- immune-mediated thrombocytopenia in the absence of other
identifiable disease is referred to as primary immune-mediated
thrombocytopenia or idiopathic thrombocytopenic purpura (ITP)
- increased levels of platelet-surface bound or serum platelet-bindable
IgG has been found in thrombocytopenic dogs with:
- SLE
- concurrent Ehrlichia canis and Babesia canis infection

- dirofilariasis
- myelodysplasia
- trimethoprim/sulfadiazene use
- neoplasia (lymphoproliferative and hemangiosarcoma)
- such findings suggest that many diseases may have an
immunologically mediated (not necessarily autoimmune) thrombocytopenia

Pathogenesis
- available evidence points to autoimmune pathogenesis for ITP

- pathogenesis of most secondary causes of immune-mediated
thrombocytopenia is unknown
- platelet destruction is mediated by antibodies bound
to the platelet surface
- antibodies are thought to be directed against normal
host platelet-surface antigens
- in humans, chronic ITP has occasionally been associated with
viral infections
- in humans, acute ITP, in about 2/3 of cases, is associated with

preceding viral infections or vaccinations
- the spleen plays a cardinal role in ITP
- in humans, the major sites of platelet destruction are
the spleen and the liver

Lewis DC, Meyers KM
Canine Idiopathic Thrombocytopenic Purpura

J Vet Intern Med, JVIM, 10[4]:207-218. Jul/Aug 1996