Tohoku J. Exp. Med., 2019 July, 248(3)

Invited Review

Indium Lung: Discovery, Pathophysiology and Prevention

TATSUYA CHONAN,1 ATSUKO AMATA,1 YOSHINORI KAWABATA2 and KAZUYUKI OMAE3

1Department of Medicine, Nikko Memorial Hospital, Hitachi, Ibaraki, Japan
2Division of Diagnostic Pathology, Saitama Prefectural Cardiovascular and Respiratory Center, Kumagaya, Saitama, Japan
3Department of Preventive Medicine and Public Health, Keio University School of Medicine, Tokyo, Japan

Indium is mainly used as indium-tin oxide (ITO), which has a unique character of transparency, and is a requisite in making liquid crystal displays. Pulmonary toxicity of indium compounds in humans were not recognized until the last 2 decades. Several initial human cases of indium-related lung disease, named indium lung, were reported in Japan, with their main pathologic findings being interstitial pneumonia, emphysema and cholesterol crystals-containing granulomas. In 2010, three cases with alveolar proteinosis were reported from the United States and China. As of March 2019, more than 10 cases of interstitial pneumonia-dominant indium lung have been reported. Cross-sectional studies in indium workers indicate that the serum indium concentration (sIn) is closely related to the exposure period, the extent of interstitial as well as emphysematous changes of the lung on high-resolution computed tomography (HRCT) and serum biomarkers of interstitial pneumonia, including KL-6 and surfactant protein-D (SP-D). Longitudinal studies have shown it is possible to reduce the sIn as well as the interstitial shadows on HRCT; however, emphysematous lesions increased progressively in heavily exposed workers, even after cessation of exposure. Early detection is required to prevent irreversible changes. The first case of lung cancer associated with indium lung developed in a nonsmoking ex-worker. He had been diagnosed with indium lung and stopped working in indium processing 17 years before. This suggested there is a need for appropriate screening to detect for complications of lung cancer at early stages for those with indium lung.

Key words —— cholesterol crystals; indium-tin oxide; interstitial pneumonia; liquid crystal displays; pulmonary alveolar proteinosis

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Tohoku J. Exp. Med., 2019, 248, 143-150

Correspondence: Tatsuya Chonan, M.D., Department of Medicine, Nikko Memorial Hospital, 2-12-8 Kamine-cho, Hitachi, Ibaraki 317-0064, Japan.

e-mail: ttchonan@mbd.ocn.ne.jp