Interstitial lung disease may occur when an injury to your lungs triggers an abnormal healing response. Ordinarily, your body generates just the right amount of tissue to repair damage. But in interstitial lung disease, the repair process goes awry and the tissue around the air sacs (alveoli) becomes scarred and thickened. This makes it more difficult for oxygen to pass into your bloodstream.

Interstitial lung disease can be triggered by many things — including autoimmune diseases, exposure to organic and inorganic agents in the home or workplace, medications, and some types of radiation. In some cases, the cause is unknown.

Occupational and environmental factors

Long-term exposure to a number of organic and inorganic materials and agents can damage your lungs. These include:

  • Asbestos fibers
  • Bird protein (live pets and feather-containing products)
  • Coal dust
  • Grain dust
  • Mold from indoor hot tubs, showers and prior water damage
  • Silica dust

Medications and radiation

Many drugs can damage your lungs, especially:

  • Chemotherapy/immunomodulating drugs, such as methotrexate and cyclophosphamide
  • Heart medications, such as amiodarone (Cordarone, Nexterone, Pacerone) and propranolol (Inderal, Inderide, Innopran)
  • Some antibiotics, such as nitrofurantoin (Macrobid, Macrodantin, others) and sulfasalazine (Azulfidine)

Some people who have radiation therapy for lung or breast cancer show signs of lung damage months or sometimes years after the initial treatment. The severity of the damage depends on:

  • How much of the lung was exposed to radiation
  • The total amount of radiation administered
  • Whether chemotherapy was also used
  • The presence of underlying lung disease

Medical conditions

Lung damage can be associated with the following autoimmune diseases:

  • Dermatomyositis/polymyositis
  • Mixed-connective tissue disease
  • Pulmonary vasculitis (microscopic polyangiitis)
  • Rheumatoid arthritis
  • Sarcoidosis
  • Scleroderma
  • Sjogren's syndrome
  • Systemic lupus erythematosus
  • Undifferentiated connective tissue disease

After extensive evaluation and testing, an explicit cause may not be found. Disorders without a known cause are grouped together under the label of idiopathic interstitial pneumonias, which are tissue-based classifications.

June 11, 2015