Learn About Bronchiolitis Obliterans

Key Facts:

  • Bronchiolitis obliterans is a rare chronic disease that worsens over time.
  • This disease was first discovered in workers at a microwave popcorn plant who had inhaled the flavoring chemical diacetyl. Thus, the bronchiolitis obliterans became known as ‘popcorn lung’.
  • This disease is not restricted to butter flavor and popcorn workers. Diacetyl is used to make many other flavors, including fruit and candy flavors, and workers in other industries who inhaled diacetyl have also been diagnosed with bronchiolitis obliterans.
  • Breathing in harmful substances is the main cause of developing the disease.
  • Bronchiolitis obliterans syndrome is the result of inflammation and scarring following lung transplantation.
  • It is important to note that the similarly named bronchiolitis obliterans organizing pneumonia (BOOP), now referred to as Cryptogenic Organizing Pneumonia (COP), is a completely different disease.

How it Affects Your Body

The very small airways of the lungs are called bronchioles. Bronchioles can become injured as a result of inhaling a harmful substance or due to an infection. Most of the time, the injury heals normally. Occasionally the cellular repair process goes into overdrive, causing the build-up of scar tissue. The thick scar tissue blocks the bronchioles and prevents air from passing through to the alveoli, or air sacs. This impairs the body's ability to absorb oxygen. The scarring and narrowing of the bronchioles may continue to worsen over time, eventually resulting in respiratory failure.

What Causes Bronchiolitis Obliterans

Bronchiolitis obliterans is most commonly caused by breathing in toxicants over time, the most common being diacetyl. Some other toxicants linked to causing bronchiolitis obliterans are:

  • Acetaldehyde, found in cannabis and e-cigarette smoke
  • Formaldehyde, a highly irritating chemical used in adhesives and building materials and emitted from e-cigarette smoke
  • Metal oxide fumes, a byproduct of welding
  • Sulfur dioxide, released by burning fossil fuels
  • Ammonia
  • Chlorine
  • Nitrogen oxides
  • Hydrochloric acid
  • Mustard gas, or sulfur mustard

Besides environmental exposure, bronchiolitis obliterans can be caused by severe respiratory infections, such as RSV, and some forms of pneumonia or bronchitis. Patients that suffer from rheumatic diseases, such as rheumatoid arthritis, are also at a higher risk of developing popcorn lung as well.

Additionally, lung transplant patients are at risk of developing the condition if their body rejects the new organ and about 50% of lung transplant recipients develop the condition within five years. This is called bronchiolitis obliterans syndrome. Other transplant patients can also be vulnerable, about 10% of people who receive a bone marrow transplant from a donor develop bronchiolitis obliterans within five years of the transplant procedure.

Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.

Page last updated: June 7, 2024

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