Interstitital Lung Disease

Interstitial lung disease is a general category that includes many different lung conditions, all of which affect the interstitium, a lace-like network of tissue in between the bronchial tubes and the blood vessels and extends throughout both lungs and is normally so thin it can’t be seen on chest X-rays or CT scans.

All forms of interstitial lung disease cause thickening of the interstitium, which can be due to inflammation, scarring, or extra fluid collection, otherwise known as edema. Some forms of interstitial lung disease are short-lived, while others are chronic and irreversible.

Some types of interstitial lung disease include drug-induced interstitial pneumonia, idiopathic pulmonary fibrosis, nonspecific interstitial pneumonitis, hypersensitivity pneumonitis, cryptogenic organizing pneumonia, acute interstitial pneumonitis, desquamative interstitial pneumonitis, sarcoidosis and asbestosis.

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Symptoms

Symptoms

The most common symptom of all forms of interstitial lung disease is shortness of breath. Nearly all people with interstitial lung disease will experience breathlessness, particularly with exertion, which may get worse over time.

Other symptoms of interstitial lung disease include dry cough and fevers, which is most common in people with cryptogenic organizing pneumonia (COP). COP is sometimes also referred to as bronchiolitis obliterans with organizing pneumonia (BOOP) and is often confused with a community acquired bacterial pneumonia. 

In most forms of interstitial lung disease, the shortness of breath develops slowly, over a period of months. However, in drug-induced interstitial pneumonias or acute interstitial pneumonitis, symptoms come on more rapidly, within hours or days.

Causes and Risk Factors

Anyone can develop interstitial lung disease, but it is more common in people with autoimmune disease, including lupus, rheumatoid arthritis, and scleroderma.

While the cause of most interstitial lung disease is unknown, some known causes include infections such as bacteria, viruses and fungi., Some interstitial lung diseases also may be caused by regular exposures at work or during hobbies to inhaled irritants, such as asbestos, silica dust, talc, coal or metal dusts from mining work, grain dust from farming and bird proteins, such as from exotic birds, chickens, or pigeons.

There are drugs which can cause interstitial lung disease in rare instances, including nitrofurantoin, amiodarone, bleomycin, and others.

Other factors that may make you more susceptible to interstitial lung disease such as pulmonary fibrosis are age, with adults being much more likely to be affected, exposure to occupational and environmental toxins, smoking, radiation and chemotherapy, and continual inhalation of very high levels of therapeutic oxygen for more than 48 hours.

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Diagnosis

People with interstitial lung disease usually come to see a doctor due to concern about shortness of breath or cough. Imaging tests of the lungs are usually done to identify the problem, starting with a simple x-ray, which may show fine peripheral lines in the lungs. Interstitial lung disease can usually be seen on a CT scan, which takes multiple x-rays of the chest and uses the images to reconstructs a detailed image of the lungs and surrounding structures.

Tests often also include pulmonary function testing, which can determine if the patient has decreased total lung capacity or a decreased ability to transfer oxygen from their lungs to their blood.

Lung biopsy, which involves obtaining a tissue sample for examination, is often necessary to tell which type of interstitial lung disease a person has. Biopsies can be done using a technique called bronchoscopy, where an endoscope is advanced through the mouth or nose into the airways and tiny tools on the end of the devise take a sample of lung tissue. Other techniques include video-assisted thoracoscopic surgery, which uses tools inserted through small incisions, or thoracotomy, a more traditional surgery involving a large incision in the chest.

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Treatments

Treatments for interstitial lung disease vary according to the type of interstitial lung disease and its cause. The most common courses of treatment are:

  • Antibiotics, which are effective against most interstitial pneumonias. Azithromycin (Zithromax) and levofloxacin (Levaquin) are the most commonly prescribed and are effective against bacterial interstitial lung diseases.
  • Corticosteroids, which reduce the activity of the immune system, lessening the associated inflammation that can sometimes lead to damage and scarring of the lungs.
  • Inhaled oxygen, which can improve symptoms for people with low oxygen blood and might also protect the heart from damage caused by low oxygen levels.
  • Lung transplant is sometimes necessary in advanced cases causing severe impairment. Most people undergoing lung transplant for interstitial lung disease make large gains in quality of life and their ability to exercise.
  • When interstitial lung disease is due to an automimmune cause, immunosuppressive drugs such as azathioprine (Imuran), mycophenolate (cell cept) and cyclophosphamide cytoxan) can be beneficial.
  • The most severe form of interstitial lung disease, idiopathic pulmonary fibrosis does not yet have a therapy that has been shown to improve lung function, but promising clinical trials are currently underway that may slow the rate of progression.