One disorder, many causes
Because interstitial lung disease has a wide range of causes, determining the reason for an initial injury to lung tissue can be difficult. Some of the many possible contributing factors include:
Occupational and environmental factors. Long-term exposure to a number of toxins or pollutants can lead to serious lung damage. Workers who routinely inhale silica dust, asbestos fibers or hard metal dust are especially at risk of serious lung disease. So are people exposed to certain chemical fumes and ammonia or chlorine gases.
But chronic exposure to a wide range of substances, many of them organic, also can damage your lungs. Among these are grain, sugar cane, and dust from bird and animal droppings. Other substances, such as moldy hay, can be a problem when they cause a hypersensitivity reaction in the lungs (hypersensitivity pneumonitis). Even bacterial or fungal overgrowth in poorly maintained humidifiers and hot tubs can cause lung damage.
Infections. These include viral infections such as cytomegalovirus, a particular problem if you have a weakened immune system; some bacterial infections, including pneumonia; fungal infections such as histoplasmosis; and parasitic infections.
Radiation. Some people who receive radiation therapy for lung cancer or breast cancer show signs of lung damage long after they finish radiation treatment. The severity of the damage may depend on how much of your lung is exposed to radiation, the total amount of radiation you receive, whether chemotherapy also is used, and whether you have underlying lung disease.
Drugs. Some drugs can damage the tissue that lines your lungs. Those most likely to cause lung problems include chemotherapy drugs, medications used to treat heart arrhythmias and other cardiovascular problems, certain psychiatric medications, and some antibiotics.
Other medical conditions. Interstitial lung disease can occur with other disorders. Often, those conditions don't directly attack the lungs, but instead affect tissue processes throughout the body. Among these are lupus, scleroderma, rheumatoid arthritis, dermatomyositis, polymyositis, Sjogren's syndrome and sarcoidosis. Some researchers think that gastroesophageal reflux disease (GERD) — in which the lungs chronically intake a small volume of gastric contents — can result in pulmonary fibrosis.