Blood hypereosinophilia in the course of posttraumatic pleural effusion.

We report four cases of posttraumatic pleural effusion associated with blood hypereosinophilia. Three men and one woman were examined at our institution for pleural effusion between 21 and 50 days after a minor thoracic trauma. At their initial examination, the pleural fluid analysis showed, for each subject, a high eosinophilic count (54, 45, 25, and 45 percent, respectively). Blood analysis taken at that time revealed a concomitant increase in the number of peripheral eosinophils (1,078, 3,894, 900, and 2,128 eosinophils per cubic millimeter, respectively). For each subject, there was no evidence of past or current allergy or of systemic disease that could be associated with hypereosinophilia. We observed a parallel regression of the pleural effusion and of the number of blood eosinophils in each case. Only when the pleural effusion completely cleared did the blood eosinophilia return to normal. We conclude that posttraumatic pleural effusion may cause a striking blood eosinophilia and that a persistently elevated number of blood eosinophils suggests the nonresolution of the pleural effusion.