Successful treatment of hypereosinophilic syndrome in a dog

An 11-year-old crossbred dog was presented with a history of episodic vomiting, diarrhoea, abdominal discomfort and coughing. These signs had been present for several years. Marked peripheral eosinophilia (10.3 x 10(9)/L) was found. No underlying cause of reactive eosinophilia was apparent. Bone marrow aspiration biopsy showed hyperplasia of the eosinophilic cell line, with some increase in immaturity, although all cells were morphologically normal. There were numerous eosinophils in bronchial wash fluid and eosinophilic infiltrates were evident in biopsies of pancreas, liver, small intestine and colon but not stomach. Hypereosinophilic syndrome was diagnosed. The dog responded well to twice daily treatment with hydroxyurea and prednisolone. Clinical signs are well-controlled 16 months later.