Interstitial Lung Disease (ILD) is a general term that includes a variety of chronic lung disorders. When a person has ILD, the lung is affected in three ways. First, the lung tissue is damaged in some known or unknown way. Second, the walls of the air sacs in the lung become inflamed. Finally, scarring (or fibrosis) begins in the interstitium (or tissue between the air sacs), and the lung becomes stiff.

Breathlessness during exercise can be one of the first symptoms of these diseases. A dry cough also may be present. These are common symptoms that many people ignore. Someone with these symptoms may wait until they feel quite ill before going to the doctor.

People with different types of ILD may have the same kind of symptoms but their symptoms may vary in severity. Their chest X-rays may look alike. Further testing is usually recommended to identify the specific type of ILD a person has. Some ILDs have known causes and some (idiopathic) have unknown causes.

Why is it called interstitial lung disease?

The tissue between the air sacs of the lungs is called the interstitium. Interstitial lung disease is named after this tissue because this is the tissue affected by fibrosis (scarring). Interstitial lung disease is sometimes also known as “interstitial pulmonary fibrosis.” The terms interstitial lung disease, pulmonary fibrosis and interstitial pulmonary fibrosis are often used to describe the same condition.

Interstitial lung diseases are puzzling

The course of these diseases is unpredictable. If they progress, the lung tissue thickens and becomes stiff. The work of breathing then becomes more difficult and demanding. Some of the diseases improve with medication if treated when inflammation occurs. Some people may need oxygen therapy as part of their treatment.

The diseases may run a gradual course or a rapid course. People with ILD may notice variations in symptoms — from very mild to moderate to very severe. Their condition may remain the same for long periods of time or it may change quickly. It’s important to stay in touch with your doctor and report any changes in symptoms. You and your doctor can work together to manage ILD.

Common link in interstitial lung disease

While the progress and symptoms of these diseases may vary from person to person, there is one common link between the many forms of ILD. They all begin with an inflammation. The inflammation may affect different parts of the lung, as explained below:

1. The walls of the bronchioles (small airways). When inflammation involves the bronchioles, it is called bronchiolitis.

2. The walls and air spaces of the aveoli (air sacs). When inflammation involves the alveoli, it is called aveolitis.

3. The small blood vessels (capillaries) of the lungs. When inflammation involves the small blood vessels, it is called vasculitis.

Inflammation of these parts of the lung may heal or may lead to permanent scarring of the lung tissue. When scarring of the lung tissue takes place, the condition is called pulmonary fibrosis.

Fibrosis, or scarring of the lung tissue, results in permanent loss of that tissue’s ability to transport oxygen. The level of disability that a person experiences depends on the amount of scarring of the tissue. This is because the air sacs, as well as the lung tissue between and surrounding the air sacs, and the lung capillaries, are destroyed by the formation of scar tissue. If this happens, your doctor may prescribe oxygen to help you breathe easier.