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Post-Infectious Bronchiolitis Obliterans

What is Post-Infectious Bronchiolitis Obliterans (BO)? 

BO is a long-lasting condition that causes narrowing and blockage of small breathing tubes (airways) in the lungs. This can cause cough, trouble breathing and noisy breathing (wheezing). Children may have trouble with activities like running and playing. Some children may also have low oxygen levels.

BO happens after injury to the lungs. This can be from infection or from other types of injury.  It can happen in people with good immune systems and in people with weak immune systems.


BO is possible when children have long lasting breathing problems after a respiratory illness. A lung scan (chest CT) may show inflammation and blockage of the small airways. Air trapping, airway widening, and damage to the airways (bronchiectasis) can be seen. If the child is older than 6 years, lung function testing can help show blockage of the small airways. If the lung scan shows enough evidence of BO, doctors may not need a lung biopsy. Sometimes a lung biopsy is needed to prove the diagnosis.

Post-infectious BO is the most common type in children. This injury to the lungs and small airways can happen after infection from a virus. Adenovirus is the most common cause of BO in children. Other viruses like influenza (the flu), parainfluenza, measles, respiratory syncytial virus (RSV) and varicella can also cause BO. Mycoplasma pneumonia (“walking pneumonia”) is a bacteria that can cause BO.

Non-infectious BO can happen after other types of injury to the lungs. These include:

  • Breathing in harmful fumes or toxin
  • An allergy to something you breathe in for a long time
  • Bad reactions to certain medicines
  • Problems with the body’s connective tissues (connective tissue diseases)
  • A skin condition called Stevens-Johnson syndrome
  • A type of rejection in people who have had lung transplant or bone marrow transplant.


Treatment of BO  should be started as early as possible. The goal is to stop more lung damage and scarring. Medicines are used to block inflammation in the lung. The most common medicines are steroids. These can be used in large doses called “pulse steroids” that are repeated monthly. In some cases, the doctor may order steroids daily by mouth (swallowed) or by inhaler (breathed in). Other medicines that fight inflammation include azithromycin and montelukast.

After the lungs are damaged, treatment is focused on supporting breathing and nutrition. Children who have significant lung damage may need to use oxygen therapy at home. If the damage is severe, they may need other support for their breathing like positive pressure. In rare cases, the lungs can keep getting worse – a lung transplant may be offered.

Your medical team will help decide which medicines to use and how long to use them. We don’t know the perfect way to treat BO right now and each child is a little different. More research is being done on the best way to care for children with BO.

What does BO mean for my child?

Usually, post-infectious BO does not get worse over years – the lung damage mostly happens during the time after the infection. Some children have a mild form of the disease and can continue to live without any breathing problems or limits to their daily life. Some children may have a more severe form of BO and need oxygen or other forms of breathing support during their life.

What to watch out for:

  • If your child is working hard to breathe, talk to a health care provider. If possible. ask to see a lung specialist who is experienced with these conditions.
  • Try to prevent infections from common childhood illnesses. Wash your hands often and ask your friends and family to let you know if they are sick before they are around your child.
  • Get your child’s vaccines and yearly flu shot.

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Author(s): Dima Ezmiga  Reviewer(s): Katelyn Krivchenia  Version: 1.0

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