Interleukin-5 levels of pleural fluid and serum samples in a patient with PIE syndrome.

An increased production of IL-5 was detected in the pleural fluid (7.2 ng/ml) and in the serum samples (53 pg/ml) of a patient with PIE syndrome. Following steroid therapy, pleural fluid disappeared, eosinophilia improved and serum IL-5 concentration became undetectable. These results suggested that eosinophilia in the PIE syndrome is a consequence of increased production of IL-5, especially in the lung.