Interstitial Lung Disease (Interstitial Pneumonitis)

Interstitial lung disease has a broad list of causes. The exact cause of interstitial lung disease is not always known (idiopathic). Some of the known common causes include toxins, environmental factors, chronic diseases, cancer, and infections. Depending on the cause, interstitial lung disease can resolve or may lead to irreversible scarring and damage to the lungs.

Known causes of interstitial lung disease include the following:

• Environmental factors, such as toxins like asbestos, mold, certain metals, silica dust, talc, grain dust, or bird droppings; interstitial disease caused by some of these irritants is referred to as "hypersensitivity pneumonitis"
• Radiation therapy to the chest
• Certain medications, including some chemotherapy (cancer-fighting) medications and the heart medication amiodarone (Cordarone)
• Chronic autoimmune diseases like rheumatoid arthritis, scleroderma, and lupus
• Infections: One of the more common infectious cause of interstitial inflammation is the bacterium Mycoplasma pneumoniae. Viruses, bacteria, and fungi can all cause interstitial inflammation.
• Cancer in some cases spreads throughout the lymph system in the lungs and appears as interstitial disease
• Congestive heart failure, renal failure both can present with similar findings due to excess fluid in the spongy tissue of the lung

Examples of idiopathic (unknown causes) forms of interstitial lung disease include:

• Bronchiolitis obliterans with organizing pneumonia (BOOP), sometimes known as cryptogenic organizing pneumonia (COP)
• Usual interstitial pneumonitis (UIP)
• Lymphocytic interstitial pneumonitis (LIP)
• Desquamative interstitial pneumonitis (DIP)
• Sarcoidosis
• Lymphangiomyomatosis
• Langerhans cell histiocytosis

The distinction among these idiopathic conditions is based on the exact pattern of lung damage, severity, and location of the disease.