Obliterative Bronchiolitis
Obliterative bronchiolitis is a rare but serious lung disease where the smallest airways become inflamed, damaged, and scarred. This scarring causes permanent narrowing of these airways, making it progressively harder to breathe. While the disease cannot be cured, treatments can help manage symptoms and slow its progression.
bronchiolitis obliterans, popcorn lung, constrictive bronchiolitis, obliterative bronchiolitis
- Bronchioles (smallest airways in the lungs)
- Lungs
Table of contents
- What is obliterative bronchiolitis?
- What causes this disease?
- Who is at risk?
- How common is this disease?
- What are the symptoms?
- How is it diagnosed?
- How is it treated?
- What is the outlook?
What is obliterative bronchiolitis?
Obliterative bronchiolitis is a disease that affects the bronchioles, which are the smallest airways in your lungs[1]. Think of your airways like the branches of a tree. As air travels through your lungs, these branches get smaller and smaller until they reach the bronchioles[2].
In this disease, inflammation or swelling occurs in these tiny airways. Over time, this inflammation causes scarring, which leads to permanent narrowing and even complete blockage of the airways[3]. This is why the condition is also known as “popcorn lung”—a nickname that came from cases discovered among workers in microwave popcorn factories who breathed in a harmful chemical called diacetyl[3].
The disease is a type of obstructive lung disease, meaning it blocks the flow of air through the lungs[2]. It usually leads to a progressive decline in lung function[2]. When this condition occurs after a lung transplant or bone marrow transplant, it is called bronchiolitis obliterans syndrome[2].
It’s important to note that obliterative bronchiolitis is different from regular bronchiolitis, which is a common viral infection in young children that usually gets better on its own[6].
What causes this disease?
There are many different causes of obliterative bronchiolitis. The disease develops when the lungs are injured in some way[3].
Breathing in toxic substances is one of the most common causes. These harmful chemicals can damage the airways and trigger the disease[2]. Some of the toxic substances include:
- Diacetyl, a flavoring chemical used in butter-flavored products like microwave popcorn[2]
- Chemicals found in electronic cigarettes and vapes[3]
- Industrial chemicals such as chlorine, ammonia, sulfur dioxide, and nitrogen oxides[2]
- Mustard gas[2]
- Metal oxide fumes[3]
Respiratory infections are another important cause, especially in children. Severe viral infections can inflame and damage the bronchioles[2]. The most common viruses that can lead to this condition include:
In children, the type caused by infection is called post-infectious bronchiolitis obliterans, and it is the most common form in this age group[6].
Organ transplants are a significant cause of this disease. After a lung transplant or bone marrow transplant, the body’s immune system may reject the new organ or cells[3]. This immune reaction can attack the lung tissue and cause inflammation and scarring in the airways[2].
Autoimmune diseases can also lead to obliterative bronchiolitis. In these conditions, the immune system mistakenly attacks the body’s own tissues[2]. The autoimmune diseases most commonly linked to this lung condition include:
Other less common causes include reactions to certain medications, severe skin conditions like Stevens-Johnson syndrome, and rare conditions such as Castleman disease[2][4]. In some cases, doctors cannot identify a specific cause, and this is called idiopathic bronchiolitis[5].
Who is at risk?
Certain people have a higher risk of developing obliterative bronchiolitis because they come into close contact with toxic substances or have certain medical conditions[3].
Workers in certain industries face increased risk due to prolonged exposure to harmful chemicals. This includes people who work in[3]:
- Microwave popcorn factories
- Coffee roasting plants
- Chemical manufacturing facilities
- Cleaning product plants
- Certain agricultural settings
Organ transplant recipients are particularly vulnerable. About 50% of people who receive lung transplants will develop bronchiolitis obliterans syndrome within five years of their surgery[3][2]. About 10% of people who receive bone marrow transplants also develop this condition within five years[3].
People who vape or use electronic cigarettes may be at risk because the liquids in these products often contain diacetyl and other harmful chemicals[3].
Children who have had severe respiratory infections are at higher risk, especially if they were infected with adenovirus or other serious viruses during infancy or childhood[6].
People with autoimmune diseases such as rheumatoid arthritis or lupus have an increased risk because their immune system may attack lung tissue[3].
How common is this disease?
Obliterative bronchiolitis is a rare disease in the general population[3][4]. The exact number of people affected is not known, but it can happen to anyone since it can result from infections or exposure to certain substances[3].
The disease is much more common in specific groups of people. More than 50% of lung transplant recipients will develop some degree of the condition within five years after their transplant[2]. The average time to diagnosis after a lung transplant is 16 to 20 months, though it has been reported as early as three months after the procedure[2].
Among people who receive bone marrow transplants, about 5% to 14% develop bronchiolitis obliterans syndrome[2]. In these cases, the condition can appear several months to years after the transplant[2].
In children, obliterative bronchiolitis is extremely rare, and we don’t know exactly how many children are affected. However, it is more likely to happen after a severe chest infection[6].
What are the symptoms?
The symptoms of obliterative bronchiolitis generally get worse over weeks to months[4]. Some people may not have symptoms initially[3]. When symptoms do appear, they may not occur until two to eight weeks after exposure to a toxic substance or after an infection[4].
The most common symptoms include[3][4]:
- Dry cough, especially during and after exercise
- Shortness of breath (also called dyspnea), particularly during physical activity
- Wheezing, which is a whistling sound when breathing
- Feeling tired or weak
Some people may also experience[3]:
- Fever
- Night sweats
- Skin rash
The cough may sometimes bring up mucus[3]. Children with the condition may have trouble breathing and difficulty with activities like running and playing[6]. Some children may also have low oxygen levels[6].
When examined by a doctor, you may have early inspiratory crackles or “squeaks” when breathing, though the chest examination may sometimes be normal[14].
How is it diagnosed?
Diagnosing obliterative bronchiolitis can be challenging because the symptoms are similar to other lung conditions[4]. Your doctor will start by asking about your symptoms and medical history, including any exposure to toxic chemicals, recent infections, or transplant procedures[6].
Imaging tests are very important for diagnosis:
A CT scan (computed tomography scan) is the most useful imaging test. The scan creates detailed pictures of your lungs[4]. A special type called a high-resolution CT scan can show a “mosaic pattern” in the lungs, which is a patchwork appearance that suggests obliterative bronchiolitis[14]. The scan is done during both breathing in and breathing out to see how well air moves through your lungs[6].
A regular chest X-ray is often normal or may only show signs of overinflation of the lungs, so it is not as helpful for diagnosis[4].
Breathing tests help measure how well your lungs are working:
Spirometry is a test where you blow into a device that measures how much air you can breathe out and how quickly[3]. This test shows airflow obstruction that doesn’t improve with medication[4]. For children under six years old, special infant breathing tests may be used[6].
Lung biopsy may be needed in some cases:
If the CT scan pictures aren’t clear enough, a doctor may need to take a small sample of lung tissue to examine under a microscope[4]. This can be done through a small cut in the chest, sometimes using keyhole surgery[6]. However, a biopsy can be difficult to interpret because the disease affects patches of the lung rather than the entire organ[14].
In many cases, if the CT scan shows enough evidence of the disease and the clinical picture fits, doctors may not need to do a lung biopsy[6].
How is it treated?
While obliterative bronchiolitis cannot be cured, treatments can help slow further worsening of the disease and manage symptoms[4].
Anti-inflammatory medications are the main treatment approach:
Corticosteroids (also called steroids) are medicines that help reduce inflammation in the lungs[4]. These can be given in different ways: as large doses called “pulse steroids” that are repeated monthly, as daily pills taken by mouth, or through an inhaler that you breathe in[6]. The goal is to block inflammation in the lung and stop more damage and scarring from occurring. Treatment should be started as early as possible[6].
Immunosuppressive medications help control the immune system’s response. These may be used along with steroids[4].
Azithromycin, an antibiotic that also has anti-inflammatory effects, may be effective in some patients, particularly those who have had lung transplants[14].
Montelukast is another medicine that can help fight inflammation[6].
Supportive treatments help with breathing:
Oxygen therapy may be needed if the lungs are damaged and cannot provide enough oxygen to the body. Some people may need to use oxygen at home[6]. This can be provided through an oxygen concentrator or oxygen machine[3].
Positive pressure support may be needed in severe cases where oxygen alone is not enough[6].
Preventing further exposure is critical. If the disease was caused by breathing in harmful chemicals, it’s essential to avoid any further contact with those substances[3].
Lung transplant may be offered in rare cases when the disease continues to get worse despite treatment and the lung damage is severe[4][6].
Each person’s treatment plan may be different. Your medical team will help decide which medicines to use and how long to use them[6]. More research is being done on the best ways to care for people with this disease[6].
What is the outlook?
The outlook for obliterative bronchiolitis varies greatly depending on the cause and how severe the disease is[5].
In general, outcomes are often poor, with many people experiencing significant long-term health problems[4]. The disease usually leads to a progressive decline in lung function[2].
However, the outlook depends on several factors:
For post-infectious cases, particularly in children, the disease usually does not get worse over the years. Most of the lung damage happens during the time after the infection[6]. Some children have a mild form of the disease and can continue to live without any breathing problems or limits to their daily life[6]. Other children may have a more severe form and need oxygen or other forms of breathing support during their life[6].
For transplant-related cases, particularly after lung transplant, the disease is a major concern. It affects about 75% of people by ten years following a lung transplant[4]. This form can be fatal if not treated[5].
For cases caused by chemical exposure, stopping further exposure is critical. If exposure is prevented early, some people may have stable disease that doesn’t get worse[5].
Some people with obliterative bronchiolitis may have mild impairment and slow progression, while others may have severe but stable disease[5]. The disease progresses in stages, but not the same way for everyone. One person might stay in an early stage for quite some time, while another progresses quickly to a more advanced stage[3].
Working closely with your healthcare provider and following the treatment plan can help improve outcomes and quality of life[5].