[Tonoko pneumoconiosis with deposition of titanium]

A 56-year-old man had worked as a furniture painter and had been exposed to tonoko polishing powder for 30 years. He had complained of dyspnea on exertion for 7 years, and was admitted to our hospital in 1991. A chest X-ray film revealed large opacities and emphysematous changes in both lung fields. Tonoko pneumoconiosis was diagnosed after transbronchial lung biopsy. Home oxygen therapy was given because of progressive hypoxemia, but the patient died of respiratory failure. At autopsy, examination of the lungs showed severe emphysematous changes, and collapse of alveoli. Many gray masses resembling coating cement were seen especially in the upper lobes. Microscopical examination showed that the large opacities were composed of hyaline nodules, similar to silicotic nodules, with anthracosis. Scanning electron microscopy with X-ray microanalysis revealed a high concentration of titanium in the gray mass. A low dose of titanium would not be expected to induce fibrotic changes in the lung, but a high dose and long-term exposure might have that effect. Titanium contained in paint might have exacerbated tonoko pneumoconiosis in this patient.