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.
Types of Interstitial Lung Disease
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. Idiopathic pulmonary fibrosis : A chronic, progressive form of fibrosis (scarring) of the interstitium. Its cause is unknown.
- Nonspecific interstitial pneumonitis: Interstitial lung disease that's often present with autoimmune conditions (such as rheumatoid arthritis or scleroderma).
- Hypersensitivity pneumonitis: Interstitial lung disease caused by ongoing inhalation of dust, mold, or other irritants.
- Cryptogenic organizing pneumonia (COP): A pneumonia-like interstitial lung disease but without an infection present. COP is also called bronchiolitis obliterans with organizing pneumonia (BOOP).
- Acute interstitial pneumonitis: A sudden, severe interstitial lung disease, often requiring life support.
- Desquamative interstitial pneumonitis: An interstitial lung disease that's partially caused by smoking.
- Sarcoidosis: A condition causing interstitial lung disease along with swollen lymph nodes, and sometimes heart, skin, nerve, or eye involvement.
- Asbestosis:Interstitial lung disease caused by asbestos exposure.
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.