Occurrence and identification of intracellular calcium crystals in pulmonary specimens.

Scanning electron microscopy, x-ray analysis studies and histochemical techniques have identified unusual birefringent intracellular calcium carbonate crystals seen in the sputum specimens of a 68-year-old man with cavitary pulmonary lesions. He was clinically diagnosed and treated for pulmonary tuberculosis. Although other etiologies are possible, we contend that the calcium salt crystals identified in the sputum in this patient represent a peripheral manifestation of tuberculosis which is rarely noticed in the sputum specimens.