Diffuse interstitial lung disease refers to a group of lung disorders in which the deep lung tissues become inflamed.

The lungs contain tiny air sacs (alveoli), which is where oxygen is absorbed. These air sacs open up or expand with each breath.

The tissue around these air sacs is called the interstitium. In people with interstitial lung disease, this tissue becomes stiff or scarred, and the air sacs are not able to expand as much. As a result, not as much oxygen can get into your lungs, and therefore to your body.

Interstitial lung diseases can be broken down into two large groups:

• Those that have no known cause (idiopathic ILD)
• Those with an identifiable cause or that occur along with other diseases

There are several types of idiopathic ILD. Idiopathic pulmonary fibrosis (IPF) is the most common type. Less common types include:

• Acute interstitial pneumonitis (AIP)
• Cryptogenic organizing pneumonia or bronchiolitis obliterans organizing pneumonia (BOOP)
• Desquamative interstitial pneumonia (DIP)
• Lymphocytic interstitial pneumonia (LIP)
• Nonspecific interstitial pneumonitis (NSIP)
• Respiratory bronchiolitis interstitial lung disease (RBILD)

There are dozens of different causes of ILD.

• Autoimmune diseases (in which the immune system attacks the body) such as lupus, rheumatoid arthritis, sarcoidosis, and scleroderma
• Certain infections
• Certain medications (such as bleomycin, amiodarone, methotrexate, gold, infliximab, etanercept)
• Radiation therapy to the chest to treat breast cancer, lymphoma, and other cancers
• Working with or around asbestos, coal dust, cotton dust, and silica dust

Cigarette smoking may increase the risk of developing some forms of ILD and may cause the disease to be more severe.