Marrow granulomas in coal workers' pneumoconiosis. A histologic study with elemental analysis.

The differential diagnosis of bone marrow granulomas is lengthy but has not previously included coal workers' pneumoconiosis. This report describes the first case in which noncaseating epithelioid granulomas containing anthracotic pigment and birefringent silica containing crystals were discovered in the marrow of a patient with progressive massive fibrosis of coal workers' pneumoconiosis. The silicotic nature of the crystals was confirmed using energy dispersive x-ray microanalysis. There was no evidence of a mycobacterial, fungal, or other etiology for the granulomas. This case demonstrates that coal workers' pneumoconiosis should be added to the differential diagnosis of bone marrow granulomas and that marrow examination may be a source of tissue for documentation of specific occupational exposures.