Abstract

Bone marrow specimens were obtained from seven workers who had been exposed to the dust of a calcareous sandstone consisting of 56·3% free silica. The pattern of changes was in the form of generalized hyperplasia, and in particular there were very high figures for the myeloid series, reticulum cells, and plasma cells. The eosinophils showed a slight but definite increase but the erythrocytes, megakaryocytes, lymphocytes, and monocytes were within the normal range. These changes were considered to be related to silicosis since other diseases causing stimulation of the bone marrow had been adequately excluded.

The findings correlate with the histopathological changes which are reported to occur in the lungs of silicotic patients; they indicate a high degree of stimulation of the reticulo-endothelial system.

If these changes are considered together with the industrial history and clinical and laboratory data, they may provide a clue to the diagnosis of silicosis and help in the differential diagnosis from other diffuse pulmonary lesions.