What are interstitial lung diseases?
Interstitial lung disease, or ILD, includes more than 100 chronic lung disorders. These diseases are not cancer and are not caused by an infection.
Interstitial lung diseases are named after the tissue between the air sacs of the lungs called the interstitium. In these diseases the interstitium is affected by scarring (fibrosis).
The symptoms and course of these diseases may vary from person to person, but the common link between the many forms of ILD is that they all begin with an inflammation.
Bronchiolitis. This is inflammation of the bronchioles (the small airways).
Alveolitis. This is inflammation of the alveoli (the air sacs where oxygen and carbon dioxide exchange in the blood takes places).
Vasculitis. This is inflammation that involves the small blood vessels (capillaries).
Most ILDs are diagnosed as:
- Pneumoconiosis or black lung disease. This is caused by inhaling coal dust.
- A drug-induced disease
- Hypersensitivity pneumonitis. This is an allergic response to breathing certain kinds of dust.
Other, less common types of ILD are:
- Sarcoidosis, in which you have small areas of inflammation in your lungs
- Idiopathic pulmonary fibrosis. This is scarring of your lungs that has no known cause.
- Bronchiolitis obliterans organizing pneumonia. This is a rare form of interstitial pneumonia.
- Histiocytosis X, which is an abnormal increase in the number of immune cells called histiocytes.
- Chronic eosinophilic pneumonia. This is a buildup of blood cells called eosinophils in your lungs.
- Collagen vascular disease. This is a connective tissue disease in which your immune system attacks your body's own tissues. This is an example of an autoimmune disease.
- Granulomatous vasculitis, which is inflammation and death of lung tissue
- Goodpasture's syndrome, in which immune cells attack lung tissue and cause bleeding in your lungs
- Pulmonary alveolar proteinosis. This means that a large amount of protein has built up in the alveoli.
In ILD, the lung is affected in 3 ways:
- Lung tissue is damaged in some known or unknown way.
- The walls of the air sacs in the lungs become inflamed.
- Scarring (fibrosis) starts in the interstitium.
Fibrosis leads to permanent loss of your lung tissue's ability to carry oxygen. The air sacs, as well as the lung tissue around the air sacs and the lung capillaries, are destroyed by the formation of scar tissue.
The diseases may run a gradual course or a rapid course. People with ILD may notice variation in symptoms, from very mild to moderate to very severe. The condition may stay the same for a long time or it may change quickly. The course of ILDs is unpredictable. If they progress, the lung tissue thickens and becomes stiff. Breathing becomes more difficult.
How are interstitial lungs diseases diagnosed?
In addition to a complete medical history and physical exam, the health care provider may also request the following tests:
Pulmonary function tests (PFTs)
These tests help to measure the lungs' ability to move air into and out of the lungs. The tests are usually done with machines into which you breathe, and may include the following:
A spirometer is a device used to assess lung function. Spirometry, the evaluation of lung function with a spirometer, is one of the simplest, most common PFTs and may be used for any or all of the following:
- To determine how well the lungs receive, hold, and move air
- To look for lung disease
- To see how well treatment is working
- To determine the severity of a lung disease
- To find out whether the lung disease is restrictive (decreased airflow) or obstructive (disruption of airflow)
Peak flow monitoring (PFM)
This device is used to measure the how fast you can blow air out of the lungs. ILD-related changes can cause the large airways in the lungs to slowly narrow. This will slow the speed of air leaving the lungs and can be measured by a PFM. This measurement is very important in evaluating how well or how poorly the disease is being controlled.
This test takes pictures of internal tissues, bones, and organs.
Arterial blood gas may be done to check the amount of carbon dioxide and oxygen in the blood. Other blood tests may be used to look for possible infections.
High-resolution computed tomography scan (HRCT, CT, or CAT scan)
An imaging procedure that uses a combination of X-rays and computer technology to produce sharp, detailed horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. HRCT scans are more detailed than regular X-rays.
This is direct exam of the main airways of the lungs (bronchi) using a flexible tube called a bronchoscope. Bronchoscopy helps to evaluate and diagnose lung problems, assess blockages, take out samples of tissue or fluid, and help remove a foreign body. Bronchoscopy may include a biopsy or bronchoalveolar lavage.
Removing cells from the lower respiratory tract to help identify inflammation and exclude certain causes.
Removing a small piece of tissue from the lung so it can be examined under a microscope.