A diffuse form of pulmonary silicosis in foundry workers.

Pulmonary silicosis usually is characterized by typical hyalinized, concentric nodules as seen under the microscope and in the corresponding roentgenogram. In the case of three foundry workers, lung biopsy specimens contained no nodules. The chest roentgenograms were not suggestive of silicosis. Examination of the biopsy tissue by scanning electron microscopy and energy dispersive x-ray analysis (EDXA) revealed significant (P less than .05) amounts of silicon in the thickened fibrous tissues of septa, pleura, and around blood vessels, enough to permit the diagnosis of silicosis. All three patients had severe functional impairment. It is not clear at this time what factors were responsible for a diffuse distribution of silicon in these cases.