What You Should Know About
Interstitial Lung Disease
It is possible to divide diseases of the lung into two broad categories, those that primarily affect the bronchial tubes of airways, and those that involve the tissues of the lung. Asthma and bronchitis are examples of the former. There are at least 130 different diseases that fit the latter category, at least two -thirds of which are caused by unknown agents.
What Happens in ILD?
In most cases of interstitial lung disease, the damage starts when some stimulus, usually totally unknown and without symptoms, causes the tissues of the lungs to become inflamed and irritated. About two-thirds of the time, it proves impossible to determine what starts this process. However, some known causes include exposure to environmental and workplace toxins, inorganic dust (such as silica and asbestos), organic dust (such as moldy hay), gases, fumes, and poisons. Some forms of therapy may also stimulate inflammation in the lungs. Among these are some chemotherapy drugs, radiation therapy, and rarely some forms of antibiotics. In most cases, the inflammatory process is present for weeks or months before it causes significant symptoms. Unfortunately, in a significant percentage of cases the disease process is not limited to the lung. Diffuse diseases that affect multiple organs may present with interstitial lung disease. For example rheumatoid arthritis involves the lung in a significant percentage of patients. Diseases such as lupus and scleraderma also have a significant pulmonary component.
Diagnosing ILD
Because there are so many causes of interstitial lung disease, it is not possible to make a general statement about diagnosis. The most common symptoms are a dry cough and slowly progressive shortness of breath. Fever, weight loss, fatigue, muscle and joint pain, and abnormal chest sounds may also be present, depending on the cause. Among the tools that are available for diagnosis are the following:
A careful and thorough medical history that includes environmental and work exposure to dust, gases, chemicals, pets, air conditioners, and humidifiers.
- A complete physical examination.
- A chest X-ray. In 90% of people with ILD, chest x-rays are abnormal.
- Pulmonary function tests. If ILD is present, there are specific tests that will be abnormal.
- Arterial blood gas measurements, which show the levels of oxygen and carbon dioxide in the blood. In many cases, the oxygen level in the blood may be normal when resting, but with exercise, will decrease.
- Bronchoscopy with bronchoalveolar lavage. In this procedure, a flexible bronchoscope is introduced into the bronchial tubes, and saline is flushed into the tissues and the air sacs. The saline solution is then withdrawn and examined to determine the nature of the inflammation that is present. In some, but not all cases, the cause of the inflammation or disease can be identified in this way.
- Open lung biopsy. This surgical procedure is usually needed to make the specific diagnosis and to determine the stage of the disease process. The procedure allows several different samples of lung tissue to be analyzed.
Treatment and Tips
No treatment can reverse scarring that has already occurred in your lungs. That's why the goals of treatment are to identify ILD as quickly as possible; remove the source of the problem, if possible; aggressively treat the inflammation; and act promptly to reduce the likelihood of complications.
Corticosteroids
These drugs - usually prednisone or methylprednisone - are the first step in treatment. For specific causes of ILD, it is sometimes possible to predict whether they will be helpful in advance, and avoid the negative aspects of corticostedroids. In any case, they should be withdrawn if no benefit is seen after one or two months.
Cyclophosphamide
Your doctor may prescribe cyclophosphamide (Cytoxan) if corticosteroid therapy doesn't have enough effect or if you can't take a corticosteroid. Cyclophosphamide reduces inflammation by killing some inflammatory cells and suppressing their function. It may take 6 months or more before you can feel the effect of the drug. In some cases, the doctor may prescribe both prednisone and cyclophosphamide. Side effects of this powerful therapy may include gastrointestinal irritation, bladder inflammation, bone marrow suppression, infection, irregular menstruation, and blood disorders.
Azathioprine
If you have problems tolerating the side effects of corticosteroids or cyclophosphamide, your doctor may prescribe azathioprine (Imuran). Although its action is similar to cyclophosphamide, it may be less effective. The benefit, however, is that it has fewer side effects. They may include fever, rash, gastrointestinal irritation, and blood disorders.
A number of new approaches to therapy are on the horizon. Some may be directed at the factors that perpetuate the inflammation, thereby attacking the inflammation directly.
Oxygen therapy
Many people with ILD need supplemental oxygen; some need it all the time, while others need it only during sleep and exercise.
Lung transplantation
If far advanced pulmonary fibrosis is present, and the disease is limited to the lung, benefit may be obtained from this major surgical procedure. With improved surgical techniques and post-transplant treatment, more centers are now able to provide single-lung, double-lung, or heart-lung transplants.
Where to Get More Information
For more information, try one of these online resources.
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