Definition and Overview

Obliterative bronchiolitis (OB) is a serious lung condition. It occurs when the smallest airways of the lungs become blocked. This can happen if a person inhales certain chemicals that inflame the airways. OB is also a common complication of lung transplantation. It occurs when the patient’s body rejects the tissues he or she received from a donor. This causes an immune response in which the body sends a huge amount of white blood cells to attack the transplanted tissue. This leads to severe inflammation and scarring.

Damage to the lung caused by OB is permanent. Its treatment focuses on preventing it from getting worse rather than curing it.

OB often occurs within four to eight weeks after a patient becomes exposed to certain chemicals. In lung transplant patients, it can occur a couple of months or several years after the surgery. It is most dangerous when it develops within the first three months after the procedure. It causes chronic lung infections and rapid decline of lung function.

OB became better known in 2000. It was during this time that a large number of factory workers suffered from it. It was later found that it was due to their exposure to chemicals used in popcorn, dairy products, and caramel. Many patients died from OB, which earned the nickname “popcorn lung.”

Causes of Condition

The main causes of OB are exposure to certain chemicals and lung transplantation. It can also occur due to certain autoimmune disorders and viral infections. It can also be a result of a severe allergic reaction to certain medications.

Key Symptoms

The first sign of OB is a dry cough that does not go away even with treatment. Other signs are wheezing and shortness of breath. These symptoms can also be caused by other respiratory disorders. For this reason, OB is often misdiagnosed during the early stages.

Who to See and Types of Treatments Available

OB is diagnosed with the following:

  • Review of medical history - Often, patients are asked to complete a form upon their arrival to the doctor’s clinic. They are asked to indicate if they have a history of lung disease, have undergone a lung transplant, or have other risk factors. These include crack cocaine use and recent viral infection. Patients are also often asked about the nature of their work. Doctors would want to know if they were exposed to certain chemicals. They would also assess the patient’s symptoms and their severity. After reviewing the patient’s medical history, the doctor will carry out a thorough physical exam to look for signs of the problem.

  • Laboratory studies - These are used to help establish a diagnosis. Patients are evaluated for infectious and autoimmune diseases that are often associated with OB.

  • Imaging studies - A chest x-ray is often the first test used to get an image of the lung. If more details are needed, the doctor will order a CT scan. This test is more effective in showing abnormalities in the organ. It can detect if the bronchial wall has thickened. It can also confirm if the airways are dilated. Such information can help doctors rule out other possible causes of the symptoms. This is important in making a definitive diagnosis.

  • Pulmonary function tests (PFTs) - These are non-invasive tests that show how well the lungs are working. They are used to measure gas exchange, rates of flow, and lung capacity. PFTs are also used in monitoring the effectiveness of treatment for OB patients.

  • Lung biopsy - This test involves obtaining a small piece of tissue from the lung. The sample tissue is then examined under a microscope. Doctors may forego this procedure in lung transplant patients.

Damage to the lungs caused by OB is permanent. This means that there is no cure for it. Doctors treat the condition with the goal of preventing it from getting worse. To achieve this, patients must not be exposed to certain chemicals. In some patients, this may mean quitting their jobs. Patients may also be given medications that limit the activity of their immune system. This will keep it from attacking the healthy cells of the lungs.

It is important for patients to undergo regular PFTs. This allows doctors to determine if their treatment is working. If their disease is progressing, doctors will need to make adjustments to achieve better treatment outcomes.

When left untreated, OB is often fatal. Thus, it is very important for patients to recognise their symptoms and seek treatment as early as possible.


  • Centers for Disease Control & Prevention and the National Institute for Occupational Safety and Health. Flavorings-Related Lung Disease fact sheet.

  • Ditschkowski M et al. Bronchiolitis obliterans after allogeneic hematopoietic SCT: further insight—new perspectives? Bone Marrow Transplantation. (2013) 48, 1224–1229.

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