What Is Interstitial Lung Disease?

Interstitial lung disease (ILD) refers to a group of more than 200 chronic disorders in which lung tissue is damaged, the walls of the air sacs become inflamed and scarring (fibrosis) begins in the interstitium -- the tissue between the air sacs. Although many of the disorders underlying interstitial lung disease are uncommon, taken together they are a frequent cause of respiratory problems, accounting for 15 percent of all lung disorders evaluated by pulmonologists.

The lung scarring associated with interstitial lung disease leads to stiffness that makes breathing difficult and interferes with the transfer of oxygen in the lungs. The pace of lung deterioration varies greatly from person to person.

Interstitial lung disease includes disorders such as pulmonary sarcoidosis, bronchiolitis obliterans organizing pneumonia, asbestosis and silicosis:

· Pulmonary sarcoidosis is an inflammatory disease in which granulomas -- small clusters of cells -- develop in the lungs and in the lymph nodes, the small groups of immune-system cells adjacent to the lungs. This disease can increase lung stiffness, which reduces lung volume.

· Bronchiolitis obliterans organizing pneumonia refers to inflammation with blockage of the bronchioles (the small airways in the lungs that branch from the large ones).

· Asbestosis and silicosis refer to damage caused by exposure to dust from asbestos and silica, respectively.

· Idiopathic pulmonary fibrosis (IPF) is a condition of unknown cause ("idiopathic") that involves progressive scarring of the lungs.

In many cases, the cause of lung injury is unknown. Factors known to be injurious to the air sacs, potentially resulting in interstitial lung disease include:

· Certain prescription drugs -- including chemotherapy drugs and cardiovascular medications

· Exposure to environmental toxins

· Infectious agents (viruses, bacteria or fungi)

· Substances (such as certain proteins in bird droppings) that set off allergic or hypersensitivity reactions in susceptible persons

· Connective tissue diseases, such as scleroderma, rheumatoid arthritis and lupus, all of which can cause inflammation and scarring of organs, including the lungs

· The spread of cancer to the lungs from other parts of the body