Interstitial lung disease is a general category that includes many different lung conditions. All interstitial lung diseases affect the interstitium, a part of the lungs' anatomic structure.
The interstitium is a lace-like network of tissue that extends throughout both lungs. The interstitium provides support to the lungs' microscopic air sacs (alveoli). Tiny blood vessels travel through the interstitium, allowing gas exchange between blood and the air in the lungs. Normally, the interstitium is so thin it can't be seen on chest X-rays or CT scans.
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Doctors may classify lung conditions as obstructive lung disease or restrictive lung disease. Obstructive lung diseases include conditions that make it hard to exhale all the air in the lungs. People with restrictive lung disease have difficulty fully expanding their lungs with air.
Obstructive and restrictive lung disease share the same main symptom: shortness of breath with exertion.
All forms of interstitial lung disease cause thickening of the interstitium. The thickening can be due to inflammation, scarring, or extra fluid (edema). Some forms of interstitial lung disease are short-lived; others are chronic and irreversible.
Some of the types of interstitial lung disease include:
Interstitial pneumonia: Bacteria, viruses, or fungi may infect the interstitium of the lung. A bacterium called Mycoplasma pneumonia is the most common cause.
Asbestosis: Interstitial lung disease caused by asbestos exposure.
Causes of Interstitial Lung Disease
Bacteria, viruses, and fungi are known to cause interstitial pneumonias. Regular exposures to inhaled irritants at work or during hobbies can also cause some interstitial lung disease. These irritants include:
Coal dust, or various other metal dusts from working in mining
Grain dust from farming
Bird proteins (such as from exotic birds, chickens, or pigeons)
All told, these factors cause a small percentage of interstitial lung disease. The cause of most interstitial lung disease is unknown.
Who is at risk from interstitial lung disease? Anyone can develop interstitial lung disease. Men and women of any age can be affected. Interstitial lung disease is more common in people with autoimmune disease, including lupus, rheumatoid arthritis, and scleroderma.