A case of idiopathic eosinophilic pneumonia in a Quarter Horse gelding

Summary A 16-year-old Quarter Horse gelding was presented to the Kansas State Veterinary Health Center for acute onset of diffuse, nonpruritic, generalised and coalescing urticaria. A single dose of dexamethasone resulted in resolution of the urticaria within 24 h; however, 48 h after discharge, he presented with mild colic. The patient was febrile and thoracic ultrasound was abnormal, evidenced by bilateral pleural echogenic irregularities, mild pulmonary consolidation and slight unilateral pleural effusion. Thoracic radiographs also revealed caudoventral soft tissue opacity in the same region of the ultrasonographic abnormalities. Transtracheal wash was performed and broad spectrum antimicrobials initiated. Poor clinical response to therapy and marked peripheral eosinophilia resulted in the necessity for bronchoalveolar lavage, which revealed a predominance of pulmonary eosinophils. A diagnosis of acute idiopathic eosinophilic pneumonia was made. Treatment included a tapering dose of dexamethasone over 4 weeks. Due to incomplete disease resolution, the patient was moved to an alternate environment which resulted in disease resolution.