Interstitial lung disease (ILD)

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.

Symptoms

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.

Causes

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

Medical conditions

Lung damage can be associated with the following autoimmune diseases:

  • Dermatomyositis/polymyositis
  • Mixed-connective tissue disease
  • Pulmonary vasculitis (microscopic polyangiitis)
  • Rheumatoid arthritis
  • Sarcoidosis
  • Scleroderma
  • 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.

Risk factors

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.

Complications

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.
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