Interstitial lung disease (ILD) is an umbrella term that covers many different conditions.
‘Interstitial’ means the disease affects the ‘interstitium’, a lace-like network of tissue that supports the alveoli (air sacs) in your lungs.
There are more than 200 different types of ILD. All of them are rare but those seen most often are covered in this information. Idiopathic pulmonary fibrosis (IPF) is the most common type of ILD.
Other common types of ILD include:
- sarcoidosis
- extrinsic allergic alveolitis (EAA)
- ILD caused by drug side effects
- ILD associated with collagen vascular diseases.
When you have ILD, inflammation or scar tissue builds up in your lungs, making them thick and hard. This build-up of scar tissue is called fibrosis. As your lungs become stiffer and lose their elasticity, they are less able to take oxygen from the air you breathe.
People with ILD can feel breathless from simple everyday activities like walking. Coughing is another common symptom.
How does ILD affect your lungs?
Each time you breathe, air is drawn into your nose or mouth, down through your throat and into your windpipe (trachea).
The windpipe splits into two smaller air tubes called the bronchi, one of which goes to the left lung and the other to the right lung. The air passes down the bronchi, which divide again and again, into thousands of smaller airways called bronchioles. This system (pictured below) is similar to branches, and its medical name is the bronchial tree.
The bronchioles have many small air sacs, called alveoli. Inside the alveoli, oxygen moves across paper-thin walls to the capillaries (tiny blood vessels) and into the blood. The alveoli also pick up the waste gas carbon dioxide from the blood, ready to be breathed out.
When your lungs are damaged by the inflammation or scarring caused by ILD, this process becomes less efficient and the oxygen you breathe can’t move easily into your bloodstream.
The diagram below shows how fibrosis due to ILD affects the air sacs in your lungs:
