An Overview of Bronchiolitis Obliterans

A.K.A. "Popcorn Lung"

Doctor examining and commenting patient's lungs X-ray.
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Bronchiolitis obliterans is a serious, irreversible lung disease that is often caused by exposure to toxins; it can also develop after a lung or bone marrow transplant. Also known as obliterative bronchiolitis and "popcorn lung," it causes symptoms similar to those of chronic obstructive pulmonary disease (COPD) or asthma, such as coughing and shortness of breath. Diagnostic tests can help distinguish these illnesses from each other.

Bronchiolitis obliterans can progress over a few weeks or months. While there is no cure, there are treatments that can help manage the effects. Despite lung transplantation being a possible cause of bronchiolitis, treatment with a lung transplant may be considered when the condition is caused by toxin exposure.

Symptoms

Generally, bronchiolitis obliterans is a disease that affects adults, but it can affect children and adolescents too. The effects generally develop over the course of a few weeks or months and may cause significant distress in your day-to-day life.

The most common symptoms of bronchiolitis obliterans are:

  • A dry cough
  • Wheezing (a loud raspy sound when breathing)
  • Dyspnea (shortness of breath)
  • Fatigue and low energy

Because bronchiolitis obliterans affects breathing, you are likely to experience exercise intolerance with this condition. You may feel extremely short of breath and exhausted after moderate physical exertion.

Once the condition begins, the effects typically worsen. In general, the symptoms are constant, persistent, and unrelated to factors such as weather (unlike asthma, which is characterized by exacerbations).

Complications

If you have bronchiolitis obliterans, you are at an increased risk of developing lung infections, such as pneumonia or bronchitis. With bronchiolitis obliterans, these infections may become severe and can make your baseline respiratory symptoms substantially worse than usual.

Bronchiolitis obliterans, like COPD, eventually leads to respiratory failure, which is a severely impaired ability to breathe enough air to supply the body with adequate oxygen. Eventually, this condition can lead to premature death.

Associated Effects

Because bronchiolitis obliterans often develops in response to toxin exposure or as a transplant complication, you may experience other associated symptoms.

For example, toxin exposure can also cause problems such as a skin rash in addition to your respiratory impairment. A lung or bone marrow transplant may also be associated with complications of chemotherapy (such as loss of appetite and decreased immunity).

You may experience these problems along with bronchiolitis obliterans.

Causes

Bronchiolitis obliterans is typically preceded by a respiratory illness, toxin exposure, or lung or bone marrow transplant. Severe inflammation in the lungs is believed to cause the condition.

The most common triggers include:

About 10% of people who receive a bone marrow transplant from a donor develop bronchiolitis obliterans within five years of the transplant procedure, while approximately 50% of lung transplant recipients develop the condition within five years.

Scarring and Inflammation of the Bronchioles

The bronchioles are tiny tubes in the lungs that carry air. When air cannot pass through the bronchioles to the alveoli (air sacs), the body's oxygen absorption becomes impaired.

Bronchioles can become damaged as a result of an infection, toxins, or inflammation. As they heal, the bronchioles may become permanently scarred. The thick scar tissue essentially "obliterates" the airway, blocking the bronchioles and preventing air from passing through. This where the name bronchiolitis obliterans stems from.

Many researchers are concerned that the chemicals diacetyl that people inhale during vaping may cause bronchiolitis obliterans. Diacetyl, a flavor-enhancing chemical, was originally used to enhance the flavor of microwave popcorn.

Why Is It Called "Popcorn Lung?"

Bronchiolitis obliterans earned the nickname "popcorn lung" after an outbreak affected a group of people who worked in a popcorn production plant. The cause was traced to inhalation of diacetyl, a chemical that was used to give microwave popcorn its buttery flavor.

Diagnosis

There are a number of causes of shortness of breath and wheezing—many of which are more common than bronchiolitis obliterans. Since the treatment of bronchiolitis obliterans is different than the treatment of other respiratory conditions, and symptoms of each can overlap, getting an accurate diagnosis is essential.

Your medical history will typically provide the biggest clue that you could have bronchiolitis obliterans. If you have had a lung or bone marrow transplant, or if you have been exposed to a toxin (especially industrial toxins), it is important that you tell your doctor.

Your physical examination is an important part of your evaluation. Your doctor will listen to your breathing sounds with a stethoscope and can detect sounds such as wheezing, which are indicative of lung disease.

Diagnostic Tests

You may need to have some diagnostic tests to help assess your respiratory function. These tests can assess the severity of your condition and help distinguish bronchiolitis obliterans from illnesses such as COPD, asthma, cancer, and heart disease.

  • Imaging tests: Your medical team can assess the structure of your lungs with a chest X-ray or computed tomography (CT) scan of the chest.
  • Pulmonary function tests: Non-invasive tests such as forced expiratory volume (FEV1) and forced vital capacity (FVC) measure the amount of air that you can breathe in and out.
  • Lung biopsy: With a surgical lung biopsy, your surgeon removes a small piece of tissue from your lung to examine it under a microscope. This is considered an accurate way to diagnose bronchiolitis obliterans. However, this test poses some risks and is not always safe after a lung transplant.

Treatment

While bronchiolitis obliterans is irreversible, there are treatments that can help prevent the progression of the disease and reduce your symptoms. If possible, be sure to avoid exposure to the precipitating toxin (if applicable) to avoid additional damage to your lungs.

It is important to be aware that bronchiolitis obliterans is expected to progress—even if you are no longer exposed to what caused it. It can be fatal if left untreated.

Medications, including corticosteroids and other immunosuppressants, can reduce inflammation. This may help prevent further scarring and disease progression. This strategy may be considered regardless of the trigger that caused you to develop bronchiolitis obliterans.

When you have bronchiolitis obliterans, your lung function may decline slowly over time, so you may need to have some of your medical tests repeated as your healthcare team assesses your disease progression and the effectiveness of your treatment.

Symptomatic Treatment

Your doctor may prescribe an inhaler for you to use. This can help alleviate your shortness of breath and wheezing. You may also be advised to use a cough suppressant if your cough is bothersome or interfering with your sleep or quality of life.

If you develop complications, such as pneumonia or bronchitis, you may need antimicrobial treatment, such as antibiotics or antifungal medications.

For late-stage bronchiolitis obliterans, you may need oxygen supplementation. Some people receive oxygen using a nasal cannula or a face mask. If you have advanced disease, mechanical ventilation may be necessary.

Lung Transplant

In some instances, a lung transplant is considered. This is major surgery. Of course, if you developed bronchiolitis obliterans as a complication of a lung transplant, another transplant might be difficult for you to physically tolerate.

A Word From Verywell

If you develop chronic lung disease, it can be difficult to exercise or to maintain moderate physical activity. It is beneficial to stay active, however. Physical therapy and pulmonary rehabilitation can help you maintain a healthy level of movement.

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Article Sources

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  1. National Center for Advancing Translational Sciences. Bronchiolitis obliterans. Genetic and Rare Diseases Information Center. Updated October 28, 2016.

  2. Estenne M, Hertz MI. Bronchiolitis obliterans after human lung transplantation. Am J Respir Crit Care Med. 2002;166(4):440-4. doi:10.1164/rccm.200201-003PP  

  3. Allen JG, Flanigan SS, Leblanc M, et al. Flavoring chemicals in e-cigarettes: diacetyl, 2,3-pentanedione, and acetoin in a sample of 51 products, including fruit-, candy-, and cocktail-flavored e-cigarettes. Environ Health Perspect. 2016;124(6):733-9. doi:10.1289/ehp.1510185

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