Interstitial (in-tur-STISH-ul) lung disease describes a large group of disorders characterized by progressive scarring of the lung tissue between and supporting the air sacs. The scarring associated with interstitial lung disease may cause progressive lung stiffness, eventually affecting your ability to breathe and get enough oxygen into your bloodstream.
Interstitial lung disease may be broadly categorized into known and unknown causes. Common known causes include autoimmune or rheumatologic diseases, occupational and organic exposures, medications, and radiation. Interstitial lung disease of unknown cause is predominated by idiopathic pulmonary fibrosis, a specific and progressive fibrotic lung disease, followed by the idiopathic interstitial pneumonias, such as nonspecific interstitial pneumonia (NSIP), and sarcoidosis.
Once lung scarring occurs, it's generally irreversible. Medications may slow the damage of interstitial lung disease, but many people never regain full use of their lungs. Lung transplant is an option for some people who have worsening interstitial lung disease despite treatment.
The primary signs and symptoms of interstitial lung disease include:
- Dry cough
- Shortness of breath at rest or with exertion
When to see a doctor
By the time symptoms appear, irreversible lung damage may have already occurred. Nevertheless, it's important to see your doctor at the first sign of breathing problems. Many conditions other than interstitial lung disease can affect your lungs, and getting an early and accurate diagnosis is important for proper treatment.
Interstitial lung disease may occur when an injury to your lungs triggers an abnormal healing response. Ordinarily, your body generates just the right amount of tissue to repair damage. But in interstitial lung disease, the repair process goes awry and the tissue around the air sacs (alveoli) becomes scarred and thickened. This makes it more difficult for oxygen to pass into your bloodstream.
Interstitial lung disease can be triggered by many things — including autoimmune diseases, exposure to organic and inorganic agents in the home or workplace, medications, and some types of radiation. In some cases, the cause is unknown.
Occupational and environmental factors
Long-term exposure to a number of organic and inorganic materials and agents can damage your lungs. These include:
- Asbestos fibers
- Bird protein (live pets and feather-containing products)
- Coal dust
- Grain dust
- Mold from indoor hot tubs, showers and prior water damage
- Silica dust
Medications and radiation
Many drugs can damage your lungs, especially:
- Chemotherapy/immunomodulating drugs, such as methotrexate and cyclophosphamide
- Heart medications, such as amiodarone (Cordarone, Nexterone, Pacerone) and propranolol (Inderal, Inderide, Innopran)
- Some antibiotics, such as nitrofurantoin (Macrobid, Macrodantin, others) and sulfasalazine (Azulfidine)
Some people who have radiation therapy for lung or breast cancer show signs of lung damage months or sometimes years after the initial treatment. The severity of the damage depends on:
- How much of the lung was exposed to radiation
- The total amount of radiation administered
- Whether chemotherapy was also used
- The presence of underlying lung disease
Lung damage can be associated with the following autoimmune diseases:
- Mixed-connective tissue disease
- Pulmonary vasculitis (microscopic polyangiitis)
- Rheumatoid arthritis
- Sjogren's syndrome
- Systemic lupus erythematosus
- Undifferentiated connective tissue disease
After extensive evaluation and testing, an explicit cause may not be found. Disorders without a known cause are grouped together under the label of idiopathic interstitial pneumonias, which are tissue-based classifications.
Factors that may make you more susceptible to interstitial lung disease include:
- Age. Interstitial lung disease is much more likely to affect adults, although infants and children are sometimes affected.
- Exposure to occupational and environmental toxins. If you work in mining, farming or construction or for any reason are exposed to environmental agents known to damage your lungs, your risk of interstitial lung disease may be increased.
- Family history. There is evidence that some forms of interstitial lung disease are heritable and your risk of developing it is increased if close family members have the disease.
- Radiation and chemotherapy/immunomodulatory drugs. Having radiation treatments to your chest or using some chemotherapy or immunomodulatory drugs may increase your risk of interstitial lung disease.
- Smoking. Some forms of interstitial lung disease are more likely to occur in people with a history of smoking, and active smoking may make the condition worse, especially if there is associated emphysema.
Interstitial lung disease can lead to a series of life-threatening complications, including:
- Acute exacerbation. Acute exacerbation is a rapid worsening of respiratory function, increased lung infiltrates seen on x-Rays and shortness of breath that are not caused by other definable processes such as congestive heart failure, blood clots in the lung or infection. Acute exacerbation can occur unexpectedly and often requires hospitalization with supportive management. It is a serious complication found in many types of interstitial lung disease.
- Gastroesophageal reflux disease (GERD). Recent studies suggest that GERD is associated with a more rapid progression of idiopathic pulmonary fibrosis, a specific form of interstitial lung disease. Patients with this disease and symptoms concerning for GERD are often treated with anti-acid medications.
- High blood pressures in the vessels of the lungs (pulmonary hypertension. Unlike systemic high blood pressure, this condition affects only the arteries in your lungs. It begins when scar tissue or low oxygen levels restrict the smallest blood vessels, limiting blood flow through the lungs. This in turn raises pressure within the pulmonary arteries. Pulmonary hypertension is a serious illness that becomes progressively worse, leading to failure or dysfunction of the right side of the heart (cor pulmonale).
- Low oxygen (hypoxemia). As lung disease progresses, oxygen support may be required both at rest and with exertion.
- Respiratory failure. In the end stage of chronic interstitial lung disease, respiratory failure occurs when severely low blood oxygen levels along with rising pressures in the pulmonary arteries and the right ventricle cause heart failure.
You'll probably first bring your symptoms to the attention of your family doctor. He or she may refer you to a pulmonologist — a doctor who specializes in lung disorders. Testing generally includes a variety of blood tests, a CT scan of the chest and pulmonary function testing.
What you can do
Before your appointment, you might want to write a list that answers the following questions:
- What are your symptoms and when did they start?
- Are you receiving treatment for any other medical conditions?
- What medications and supplements have you taken in the past five years, including over-the-counter medications or illicit drugs?
- What are all the occupations you've ever had, even if only for a few months?
- Do you own any air conditioners, humidifiers, hot tubs, or were exposed to water damaged walls or carpet?
- Do you own any pet birds or any feather or down containing products (pillows, blankets, clothes)?
- Do any members of your family have a chronic lung disease of any kind?
- Have you ever received chemotherapy or radiation treatments for cancer?
- Do you have any other medical conditions, especially inflammatory or autoimmune diseases?
- Did you have any blood work done looking for inflammatory or autoimmune diseases?
- Did you undergo a tissue sampling from your lungs?
If your primary care physician had a chest X-ray done as part of your initial evaluation, bring that with you when you see a pulmonologist. It will help the pulmonologist make a diagnosis if he or she can compare an old chest X-ray with the results of a current X-ray. The actual X-ray image is more important to your doctor than is the report alone. CT scans of your chest also may have been done, and those should also be requested.
What to expect from your doctor
Your doctor will do a thorough history and examination, and review important testing you may have had done prior to your visit. If necessary, your doctor may obtain further X-rays, blood work or breathing test, and perhaps discuss with you the possibility of obtaining a tissue sample.
Identifying and determining the cause of interstitial lung disease can be challenging. A portion of disorders may fall into this broad category. In addition, the signs and symptoms of a wide range of medical conditions can mimic interstitial lung disease, and doctors must rule these out before making a definitive diagnosis. Some of the following tests may be necessary.
- Chest X-ray. The lung damage associated with many types of interstitial lung disease often shows up in characteristic patterns on chest X-rays. Occasionally, the chest X-ray is normal and further tests are required to explain your shortness of breath. In some diseases (sarcoidosis), chest X-rays may also be used to track the progression of disease.
- Computerized tomography (CT) scan. CT scanners use a computer to combine X-ray images taken from many different angles to produce cross-sectional images of internal structures. A high-resolution CT scan can be particularly helpful in determining the extent of lung damage caused by interstitial lung disease. It can reveal details and patterns of fibrosis, which can be helpful in narrowing down the diagnosis.
- Echocardiogram. A sonogram for the heart, an echocardiogram uses sound waves to visualize the heart. It can produce still images of your heart's structures, as well as videos that show how your heart is functioning. This test can be used to assess abnormal pressures in the right and left sides of your heart.
Pulmonary function tests
- Oximetry. This test uses a small device placed on one of your fingers to measure the oxygen saturation in your blood during and while walking. If there is concern about low oxygen levels while you're asleep, the test can be performed overnight.
- Spirometry and diffusion capacity. This test requires you to exhale quickly and forcefully through a tube connected to a machine that measures how much air your lungs can hold, and how much is moving out of your lungs. It also measures how easily oxygen can move from the lungs into the bloodstream.
Lung tissue analysis
Often, pulmonary fibrosis can be better defined by examining a small amount of lung tissue (biopsy) in a laboratory. The tissue sample may be obtained in one of these ways:
- Bronchoscopic biopsy. In this procedure, your doctor removes very small tissue samples — generally no larger than the head of a pin — using a small, flexible tube (bronchoscope) that's passed through your mouth or nose into your lungs. The serious risks of bronchoscopic biopsy include bleeding or a deflated lung, which may require treatment. More common side effects are temporary sore throat and hoarseness.
- Surgical biopsy. Although this is a more invasive procedure with potential complications, it's often the only way to obtain a large enough tissue sample to make an accurate diagnosis. During the procedure under general anesthesia, surgical instruments and a small camera are inserted through two or three small incisions between your ribs. The camera allows your surgeon to view your lungs on a video monitor while removing tissue samples from your lungs.
The lung scarring that occurs in interstitial lung disease is often irreversible, and treatment will not always be effective in stopping the ultimate progression of the disease. Some treatments may improve symptoms temporarily or slow disease progress. Others help improve quality of life. Because many of the different types of scarring disorders have no approved or proven therapies, clinical studies may be an option to receive an experimental treatment.
Depending on the underlying cause of interstitial lung disease, treatments fall into two categories: anti-inflammatories or anti-fibrotics. Interstitial lung disease that has a known inflammatory or autoimmune process may benefit from initial anti-inflammatory or immunosuppressing medications. If there is a known exposure, avoiding the inciting agent is a first step to treatment. Specifically for idiopathic pulmonary fibrosis, there are two medications now available for slowing the scarring process. Your doctor may work with other doctors, such as a rheumatologist or cardiologist, to optimize your care.
Using oxygen can't stop lung damage, but it can:
- Make breathing and exercise easier
- Prevent or lessen complications from low blood oxygen levels
- Reduce blood pressure in the right side of your heart
- Improve your sleep and sense of well-being
You're most likely to receive oxygen when you sleep or exercise, although some people may use it round-the-clock.
Lung transplantation may be an option of last resort for people with severe interstitial lung disease who haven't benefited from other treatment options.
Being actively involved in your own treatment and staying as healthy as possible are essential to living with interstitial lung disease. For that reason, it's important to:
- Stop smoking. If you have lung disease, the best thing you can do for yourself is to stop smoking. Talk to your doctor about options for quitting, including smoking cessation programs, which use a variety of proven techniques to help people quit. And because secondhand smoke can also be harmful to your lungs, don't allow other people to smoke around you.
- Eat well. People with lung disease may lose weight both because it's uncomfortable to eat and because of the extra energy it takes to breathe. These people need a nutritionally rich diet that contains adequate calories. A dietitian can give you further guidelines for healthy eating.
- Remain active. As much as you can tolerate, continue to exercise and remain active to avoid deconditioning.
- Get vaccinated. Respiratory infections can worsen symptoms of intersitial lung disease. Make sure you receive the pneumonia vaccine and an annual flu shot.
Living with a chronic lung disease is emotionally and physically challenging. Your daily routines and activities may need to be adjusted, sometimes radically, as breathing problems worsen or health care needs take priority in your life. Feelings of fear, anger and sadness are normal as you grieve for the loss of your old life and worry about what's next for you and your family.
Share your feelings with your loved ones and your doctor. Talking openly may help you and your loved ones cope with the emotional challenges of your disease. In addition, clear communication will help you and your family plan effectively for your needs if your disease progresses.
You may also want to consider joining a support group, where you can talk to people who are facing challenges similar to yours. Group members may share coping strategies, exchange information about new treatment or simply listen as you express your feelings. If a group isn't for you, you may wish to talk with a counselor in a one-on-one setting.