Hypereosinophilic syndrome in a cat with eosinophilic enteritis and recurrent eosinophilic pericardial effusion

Abstract A 9‐year‐old, spayed, female Russian Blue cat with a history of weight loss and a suspected collapse episode was evaluated. Bloodwork revealed marked eosinophilia, and endoscopic biopsies confirmed lymphoplasmacytic and eosinophilic enteritis. One week later, the cat re‐presented for collapse associated with pericardial effusion and tamponade. Pericardial fluid analysis revealed predominant eosinophils (79%). The echocardiogram showed normal cardiac structure and function. A diagnosis of feline hypereosinophilic syndrome was made. Despite starting glucocorticoids, the first‐line treatment of eosinophilic inflammatory diseases, the disease progressed. The patient presented following another collapse episode with recurrent pericardial effusion and tamponade. Recheck echocardiogram revealed the development of moderate left ventricular hypertrophy, and the patient was euthanased. This paper outlines the presentation, treatment and postmortem findings of a feline patient diagnosed with suspected hypereosinophilic syndrome with cardiac involvement. Although hypereosinophilic syndrome is well described in human literature, there is a lack of case reports describing cardiac involvement in veterinary patients.