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 ILD 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 ILD 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
  • 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 that are 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 (which is the meaning of "idiopathic") that involves progressive scarring of the lungs.

Causes of Interstitial Lung Disease

A variety of factors can injure the air sacs and result in ILD. Possible causes 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
  • spread of cancer to the lungs from other parts of the body

In many cases, however, the cause of lung injury is unknown.

Interstitial Lung Disease Symptoms

Symptoms vary widely depending on the specific disease, but most people with ILD become short of breath when they exert themselves and have a persistent cough that does not produce phlegm. Fatigue, loss of appetite, and weight loss are common in ILD; wheezing, chest pain, coughing up blood, and fever also are possible.

Depending on the underlying cause, the disease may last for only a few weeks. More often, however, symptoms persist for months or years.

Publication Review By: Peter B. Terry, M.D., M.A.

Published: 09 Aug 2011

Last Modified: 23 Jan 2015