Eosinophilic pleural effusion: is it always nondiagnostic?

The presence of eosinophils in the pleural effusion is generally considered nondiagnostic. It usually indicates that the patient has had a previous thoracentesis and that air or blood has come in contact with the effusion. Idiopathic acute eosinophilic pneumonia is characterized by acute onset of pulmonary symptoms with hypoxemia, pulmonary infiltrates, eosinophils in bronchoalveolar lavage fluid, and prompt response to steroid therapy. We report a patient who presented with symptoms of acute pneumonia in which the presence of increased eosinophils in the pleural effusion indicated eosinophilic pneumonia.