Valproic acid-induced eosinophilic pleural effusion.

Valproic acid is a carboxylic acid used for the treatment of both seizure and mood disorders. Its association with pleural fluid eosinophilia has been reported once in the English language literature. We present another case of valproic acid-induced pleural fluid eosinophilia associated with fever and peripheral blood eosinophilia. Extensive evaluation failed to reveal any other cause of eosinophilic pleural effusion, and the effusion resolved with discontinuance of valproic acid. Rechallenge with valproic acid produced recurrent symptoms. Valproic acid should be considered a possible cause of eosinophilic pleural effusion.