Eosinophilic leukaemoid reaction in a dog

Investigation of hypereosinophilia and potential treatments

Hypereosinophilia is excessive eosinophilia and has been defined in dogs and cats as eosinophils greater than 5 x 10(9)/L (> 5000/microL). Canine breeds with a predisposition to higher eosinophil counts or certain eosinophilic diseases include the Rottweiler, German Shepard, Siberian Husky, Alaskan Malamute, and Cavalier King Charles Spaniel. Two of the more common causes of canine hypereosinophilia are pulmonary infiltrates with eosinophils (PIE) and gastrointestinal disease. The highest eosinophil counts are expected in dogs with pneumonia or PIE. The most common cause of eosinophilia in cats is flea allergy. The greatest eosinophilia occurs in cats with flea allergy, feline asthma, and eosinophilic granuloma. Innovative recent treatments for human patients with asthma have been successful in reducing eosinophil numbers but have had a confusing and disappointing lack of reducing symptoms. The role of eosinophils in many eosinophilic diseases remains a mystery.

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.