Indium lung is a rare

occupational lung disease Occupational lung diseases comprise a broad group of diseases, including occupational asthma, industrial bronchitis, chronic obstructive pulmonary disease (COPD), bronchiolitis obliterans, inhalation injury, interstitial lung diseases (such as ...

caused by exposure to respirable

indium Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...

in the form of

indium tin oxide Indium tin oxide (ITO) is a ternary composition of indium, tin and oxygen in varying proportions. Depending on the oxygen content, it can be described as either a ceramic or an alloy. Indium tin oxide is typically encountered as an oxygen-saturate ...

. It is classified as an

interstitial lung disease Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of respiratory diseases affecting the interstitium (the tissue) and space around the alveoli (air sacs) of the lungs. It concerns alveolar epithelium, pulm ...

(diffuse parenchymal lung disease). The indium industry is primarily based in Japan, where the majority of cases have been reported.

Signs and symptoms

The major signs of indium lung are pulmonary alveolar proteinosis and pulmonary fibrosis. Symptoms include

dyspnea Shortness of breath (SOB), known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing discomfort that ...

(shortness of breath), cough, and increased

sputum Sputum is mucus that is coughed up from the lower airways (the trachea and bronchi). In medicine, sputum samples are usually used for a naked-eye examination, microbiological investigation of respiratory infections, and Cytopathology, cytological ...

production.

Hemoptysis Hemoptysis or haemoptysis is the discharge of blood or blood-stained sputum, mucus through the mouth coming from the bronchi, larynx, vertebrate trachea, trachea, or lungs. It does not necessarily involve coughing. In other words, it is the airw ...

has also been seen in people with indium lung. Other symptoms seen in some but not all cases include digital clubbing, low

DLCO DLCO or TLCO ( diffusing capacity or transfer factor of the lung for carbon monoxide (CO),) is the extent to which oxygen passes from the air sacs of the lungs into the blood. Commonly, it refers to the test used to determine this parameter. It w ...

(capacity to move oxygen from the alveoli into the blood), and lowered forced expiratory volume.

Emphysema Emphysema is any air-filled enlargement in the body's tissues. Most commonly emphysema refers to the permanent enlargement of air spaces (alveoli) in the lungs, and is also known as pulmonary emphysema. Emphysema is a lower respiratory tract di ...

has been associated with indium lung, but may not be part of the syndrome.

Complications

Lung cancer may be related to indium lung disease, though indium is not a known carcinogen.

Causes

Indium lung is caused by exposure to

in a variety of occupational contexts, including reclamation and production. Exposure to indium tin oxide as it reacts can lead to exposure to indium metal, indium hydroxide, and indium oxide.

Mechanism

The exact mechanism of pathogenesis is unknown, but it is hypothesized that indium may exacerbate existing autoimmune disorders or that

phagocytosis Phagocytosis () is the process by which a cell (biology), cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs ph ...

of indium by

alveolar macrophage An alveolar macrophage, pulmonary macrophage, (or dust cell, or dust eater) is a type of macrophage, a phagocytosis#Professional phagocytic cells, professional phagocyte, found in the airways and at the level of the pulmonary alveolus, alveoli in ...

s may cause dysfunction in the macrophages.

Diagnosis

CT scanning and

radiography Radiography is an imaging technology, imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical ("diagnostic" radiog ...

can be used to aid in the diagnosis of indium lung. CT abnormalities include ground-glass opacities, interlobular septal thickening, honeycombing, and

bronchiectasis Bronchiectasis is a disease in which there is permanent enlargement of parts of the bronchi, airways of the lung. Symptoms typically include a chronic cough with sputum, mucus production. Other symptoms include shortness of breath, hemoptysis, co ...

Laboratory findings

Multiple abnormal laboratory findings have been noted in indium lung. High levels of serum indium have been found in all cases of indium lung. Other abnormal laboratory values that have been found include elevated alanine aminotransferase, elevated aspartate aminotransferase, elevated

C-reactive protein C-reactive protein (CRP) is an annular (ring-shaped) pentameric protein found in blood plasma, whose circulating concentrations rise in response to inflammation. It is an acute-phase protein of hepatic origin that increases following interleukin ...

, elevated interstitial lung disease markers, and elevated GM-CSF

autoantibodies An autoantibody is an antibody (a type of protein) produced by the immune system that is directed against one or more of the individual's own proteins. Many autoimmune diseases (notably lupus erythematosus) are associated with such antibodies. Pr ...

Prevention

The National Institute of Occupational Safety and Health, Japan (JNIOSH) set limits for acceptable exposure at 0.0003 mg/m³ after the discovery of indium lung. Methods for reducing indium exposure are thought to be the best mode of protection. Medical surveillance of indium workers is also a method of prevention.

Treatment

There is no standardized treatment for indium lung disease. Treatment options include pulmonary lavage and

corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invo ...

therapy.

Prognosis

Prognostic factors were a matter of research as of 2012, but preliminary evidence suggests that duration of employment and reported use of respiratory protection are not prognostic factors, but the serum level of indium may be a prognostic factor - higher levels of serum indium have been associated with worse prognoses. Indium lung disease has been fatal in several cases.

History

It was first described by a group of Japanese researchers in 2003.

Epidemiology

Cases have been reported in

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

, the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, and

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. The indium industry is mainly based in Japan, where the bulk of cases have occurred; indium industry is also present in the US, China,

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...