Canine idiopathic thrombocytopenia: clinical observations and long-term follow-up in 54 cases.

Idiopathic thrombocytopenia purpura (ITP) was diagnosed in 54 dogs. Bleeding was associated with platelet counts less than or equal to 30,000/mm3, and occurred most frequently at mucosal surfaces and in the skin. Other hematologic changes were variable, the most common being regenerative anemia with leukocytosis. Bone marrow examination revealed variable megakaryocyte numbers, but hyperplasia was most commonly observed. Results of the platelet factor 3 test were positive in only 7 of 25 dogs so tested. Treatment included various combinations of corticosteroid, vincristine, cyclophosphamide, and splenectomy. The dogs could be classified into 4 groups on the basis of the course of disease: (1) 14 dogs that died or were euthanatized during the first episode of thrombocytopenia, (2) 17 dogs that recovered after a single episode of thrombocytopenia (acute ITP), (3) 8 dogs in which thrombocytopenia recurred over a period of up to 8 months before recovering (acute, recurrent ITP), and (4) 15 dogs that experienced repeated episodes of ITP for periods of up to 8 years (chronic ITP).