Immunologic diseases of the pleura.

This heterogeneous group of immunologic causes of pleural effusions includes connective tissue diseases, a syndrome related to tissue injury (postcardiac injury syndrome), a disease of unknown etiology (sarcoidosis), a malignancy, and adverse reactions to drugs. Except in rheumatoid pleurisy and lupus pleuritis, the pleural fluid findings are either nonspecific or have not been characterized fully. The clinical presentation is essential in the presumptive diagnosis of these causes of pleural effusions.