Page 3 - AITP AutoImmune Thrombocytopenia

A direct test for the presence of antiplatelet antibodies—an ELISA that detects platelet‐bound
antibodies—has been reported to have good sensitivity (94%) but is not highly specific for primary
immune‐mediated thrombocytopenia. A negative test result likely excludes primary immune‐mediated
thrombocytopenia as the cause of thrombocytopenia; however, a positive test result could indicate
either primary immune‐mediated thrombocytopenia or secondary immune‐mediated
thrombocytopenia (eg, thrombocytopenia associated with autoimmune hemolytic anemia,
lymphoproliferative diseases, systemic lupus erythematosus).

Affected animals should be kept at rest, and treatment is based on administration of corticosteroids,
starting at a high dose and then tapering (as in the treatment of Hemolytic Anemia). Transfusion with
fresh whole blood should be performed in animals with a PCV <15%; however, whole blood transfusion
to replenish platelets is often futile with regard to normalization of primary hemostasis, because the
platelets are removed from circulation within a couple of hours. Splenectomy should be reserved as a
treatment for animals that have recurrent episodes of thrombocytopenia. Vincristine has been used to
enhance the release of platelets from marrow megakaryocytes. It also coats platelets and has a
cytotoxic effect on macrophages that ingest coated platelets. A single dose of vincristine at the time
corticosteroids are started shortens the time to recovery of the platelet count.

Rickettsial Diseases:

Anaplasma platys, A phagocytophilum, or Ehrlichia canis infections cause mild to severe
thrombocytopenia in dogs. A platys infection (see Ehrlichiosis and Related Infections) usually is
characterized by mild, often cyclic thrombocytopenia in the acute stages of disease. Chronic infections
often have constant mild to moderate thrombocytopenia. Morula (single to multiple, round to oval
basophilic inclusions) can sometimes be identified in platelets of infected dogs. The thrombocytopenia is
seldom severe enough to result in clinical bleeding tendencies. Ticks are the likely vectors. E canis
infections are characterized by variable alterations in total WBC count, PCV, and platelet count. In acute
infections, there is usually thrombocytopenia and possibly anemia or leukopenia. In chronic infections,
there may or may not be thrombocytopenia or anemia; however, there is often leukocytosis and
sometimes hyperglobulinemia (monoclonal or polyclonal). Infected dogs may have epistaxis, melena,
gingival bleeding, retinal hemorrhage, hematoma formation, and prolonged bleeding after venipuncture
or surgery.

A phagocytophilum infection has been documented in a wide variety of domestic and wild animals. It is
characterized by fever, lethargy, and a reluctance to move. Changes in blood parameters include
thrombocytopenia and lymphopenia accompanied by increased serum alkaline phosphatase and
hypoalbuminemia.

Neoplasia: