Nonspecific interstitial pneumonia (NSIP)
What is nonspecific interstitial pneumonia?
Nonspecific interstitial pneumonia (NSIP) is a rare disorder that affects the tissue that surrounds and separates the tiny air sacs of the lungs. These air sacs, called the alveoli, are where the exchange of oxygen and carbon dioxide takes place between the lungs and the bloodstream. Interstitial pneumonia is a disease in which the mesh-like walls of the alveoli become inflamed. The pleura (a thin covering that protects and cushions the lungs and the individual lobes of the lungs) might become inflamed as well.
NSIP can be found in a number of different diseases, including connective tissue disorders (diseases that affect the structural tissues in the body), reactions to certain medications, HIV, as well as other conditions. A large number of patients also have idiopathic NSIP, which means that the specific cause of the lung disease is unknown.
There are two primary forms of NSIP - cellular and fibrotic. The cellular form is defined mainly by inflammation of the cells of the interstitium. The fibrotic form is defined by thickening and scarring of lung tissue. This scarring is known as fibrosis and is irreversible. When the lung tissue thickens or becomes scarred, it does not function as effectively. Breathing becomes less efficient, and there are lower levels of oxygen in the blood.
Both inflammation and fibrosis may be present at the same time. Generally, the prognosis is better for patients with the cellular form of NSIP.
What are the symptoms of nonspecific interstitial pneumonia?
A person may have these symptoms:
- a dry cough
- shortness of breath, which may occur after effort or become worse over time
- difficult or labored breathing
- clubbing, or enlargement of the fingertips at the base of the nails. Clubbing may be present due to a lack of oxygen in the blood. Generally, this occurs in only about 10% of people with NSIP.
How common is NSIP?
NSIP has only been defined for a relatively short time, and less is known about how common it is versus other kinds of interstitial pneumonia. Caucasians appear to account for most of the cases, with an average age of onset between 40 and 50 years. There does not seem to be a correlation between cigarette smoking and NSIP.
What causes NSIP?
No one is really sure what causes NSIP. Many researchers believe that it is an autoimmune disease, because of the similarities between NSIP and certain connective tissue diseases, such as systemic sclerosis. Some researchers suggest that genes are involved, with heredity playing a role in its development. Inhaling chemicals or dust, use of certain chemotherapy drugs, or radiation treatment could result in the lung damage associated with NSIP.
How is NSIP diagnosed?
Because the symptoms of NSIP resemble those of other diseases, especially idiopathic pulmonary fibrosis, tests must be performed to rule out other related disorders. The diagnosis of the disease depends on a combination of clinical, radiologic and other factors.
Pulmonary function tests may be ordered to assess how well the lungs are working and the rate of carbon dioxide and oxygen exchange.
Generally, a high-resolution computed tomography (CT) scan is performed to help diagnose NSIP. CT scans of patients with NSIP show a typical "ground glass" pattern that represents interstitial inflammation, and is usually seen in the cellular form. Scarring, or fibrosis, will be seen in the fibrotic form.
Occasionally, a bronchoscopy is performed to aid in the diagnosis of the disease. A flexible tube called a bronchoscope is inserted into the bronchi (air passages) of the lung, and a saline fluid is passed through the bronchoscope. After coming into contact with the airways and alveoli, the fluid is aspirated (sucked out) and collected for further analysis. This is called a bronchoalveolar lavage. Elevated levels of lymphocytes (white blood cells) in the fluid have been detected in over half of patients with NSIP, but this is not always specific to this disease. Biopsies may also be taken during the bronchoscopy to get a closer look at the lung tissue for inflammation or scarring. In many patients, a surgical lung biopsy may be necessary to make a definitive diagnosis.
How is NSIP treated?
Most patients with the cellular type of NSIP respond well to treatment with oral corticosteroids, such as prednisone. However, patients who do not respond to corticosteroid therapy may require additional treatment with immune-suppressing drugs. Patients with the fibrotic type of NSIP might benefit from the use of both types of drugs to prevent further irreversible fibrosis.
The prognosis for patients with cellular NSIP is excellent, with a low mortality rate. In the case of fibrotic NSIP, the prognosis is less favorable, with a median survival period of 6 to 13.5 years after diagnosis.
"Classification and Natural History of the Idiopathic Interstitial Pneumonias" Dong Soon Kim, Harold R. Collard and Talmadge E. King www.ncbi.nlm.nih.gov Accessed 1/12/2015.
"Nonspecific Interstitial Pneumonia: Evolving Concepts" www.radiology.rsna.org Accessed 1/12/2015.
Idiopathic Nonspecific Interstitial Pneumonia: Lung Manifestation of Undifferentiated Connective Tissue Disease? www.ncbi.nlm.nih.gov Accessed 1/12/2015.
"Idiopathic interstitial pneumonias: progress in classification, diagnosis, pathogenesis and management" www.ncbi.nlm.nih.gov Accessed 1/12/2015.
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