Eosinophilic Pleural Effusion: A Rare Manifestation of Hypereosinophilic Syndrome

Several causes of eosinophilic pleural effusions have been described with malignancy being the commonest cause. Hypereosinophilic syndrome (HES) is a rare disease and very few cases have been reported of HES presenting as eosinophilic pleural effusion (EPE). We report a case of a 26-year-old male who presented with shortness of breath. He had bilateral pleural effusions, generalized lymphadenopathy, splenomegaly, and leukocytosis with marked peripheral blood eosinophilia. The pleural fluid was exudative, with 25%-30% eosinophilis, and absence of neoplastic cells. Hypereosinophilic syndrome was diagnosed after other causes of eosinophilia were excluded. He continued to be dyspneic with persistent accumulation of eosinophilic pleural fluid, even after his peripheral eosinophil count had normalized in response to treatment. This patient represents a very unusual presentation of HES with dyspnea and pleural effusions and demonstrates that treatment based on response of peripheral eosinophil counts, as is currently recommended, may not always be clinically adequate.