Myocardial infiltration with immature cells in hypereosinophilic syndrome

A case of hypereosinophilic syndrome is reported. Investigation failed to reveal any precipitating cause or evidence of leukaemia. Death was due to intractable cardiac failure, and post-mortem examination showed infiltration of the myocardium with sheets of immature cells. The relevance of these cells is discussed and further investigation such as cardiac biopsy is suggested for similar cases.