Successful treatment of suspected essential thrombo-cythaemia in the dog

Essential thrombocythemia in a dog

A two-year old male Welsh Corgi was referred for persistent thrombocytosis and occasional seizure. Hematological findings indicated marked thrombocytosis, eosinophilia, basophilia and moderate anemia. Bone marrow examination revealed marked megakaryocytic hyperplasia with morphologic abnormality. A diagnosis of essential thrombocythemia was made and the treatment was initiated with combination chemotherapy and maintained by prednisolone and busulfan. The dog successfully achieved complete remission on 100 days after initial presentation and has been good in health without chemotherapy since then.

Diagnostic and hematologic features of probable essential thrombocythemia in two dogs

The clinical and hematologic features of two cases of probable essential thrombocythemia in the dog are described. Both dogs presented with hepatosplenomegaly, severe nonregenerative anemia, neutrophilia and Thrombocytosis. Mean platelet volume and percentages of large platelets were markedly increased in both dogs. Platelet aggregation studies demonstrated hyperaggregability in one dog; platelets from the other dog aggregated spontaneously, precluding further investigation. Cytologic and histologic examination of bone marrow showed pronounced megakaryocytic hyperplasia, with erythroid hypoplasia and relative myeloid hyperplasia. Megakaryocyte morphology was abnormal, with increased numbers of small mononuclear and binucleate cells. Normal to increased hemosiderin stores suggested that apparent macrocytosis in one dog, rather than being due to iron deficiency, resulted from the hematology analyzer counting large platelets as small red blood cells. Megakaryocytic infiltration of the spleen was evident in both dogs. The hematologic findings in dogs with essential thrombocythemia can mimic those associated with iron deficiency anemia, such that diagnostic investigations should be aimed at ruling out chronic blood loss and other causes of reactive Thrombocytosis.