What Causes Hardening of the Lungs?

Different parts of the lungs have different functions. The airways are responsible for transmitting gases between the lungs and the environment. The alveoli are millions of tiny sacs in the lungs that exchange gases between the lungs and the blood. The interstitium includes the tissues between the alveoli and airways. This tissue is elastic, allowing the lungs to expand during inspiration and helping them to contract during expiration, like a rubber band. Some diseases damage these tissues, making the lungs inelastic, preventing them from expanding and contracting, and causing breathing difficulty. These are called interstitial lung diseases.

Doctor and patient looking at chest X-ray (Image: AlexRaths/iStock/Getty Images)

Drugs and Inhaled Substances

Exposure to certain inhaled substances, such as at work, can lead to interstitial lung disease. When this happens, it is called occupational lung disease. Silica, beryllium and asbestos are examples of such substances. In addition, some drugs cause interstitial lung disease in certain people. Amiodarone is one such drug. It is used to treat irregular heart rhythms. Some antibiotics and chemotherapy drugs may also be responsible for interstitial lung disease.


Being infected with certain organisms, including the bacterium that causes tuberculosis and the respiratory syncytial virus, can also lead to interstitial lung disease.

Connective Tissue Diseases

Connective tissue diseases are diseases that affect connective tissues throughout the body. These diseases can also affect the lungs, though not in every case. Lupus is a chronic disease in which the immune system attacks the organs and tissues such as the heart, lungs, joints, skin and kidneys. Rheumatoid arthritis is a disease that primarily affects the joints but can affect the organs such as the lungs.

Idiopathic Diseases

Some diseases have an unknown cause; these are called idiopathic diseases. Idiopathic pulmonary fibrosis is a disease of the connective tissue of the lungs in which, for unknown reasons, the elastic tissues are replaced by scar tissue. Sarcoidosis is a disease in which nodules of tissue grow in the lungs and other organs.

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