The pleural manifestations of asbestos exposure.

Pleural abnormalities are the most common disease manifestations of asbestos exposure and have both clinical and epidemiologic implications. Benign pleural processes include pleural thickening, which can be discrete (plaques) or diffuse, rounded atelectasis (pseudotumor), and benign exudative asbestos effusions. Asbestos is the most significant cause of diffuse malignant mesothelioma. Most patients with discrete pleural thickening have normal pulmonary function. Patients with extensive pleural involvement, however, can have significant restrictive impairment with no or only minimal interstitial disease. For any given radiological grade of parenchymal disease, pulmonary function is more impaired when pleural thickening is present. The presence of typical pleural changes can serve as a reliable marker for asbestos exposure in epidemiologic studies. Individuals with pleural plaques are more likely to develop parenchymal involvement than similarly exposed workers without pleural disease. Once present, pleural changes are likely to progress even in the absence of further exposure.