What is Bronchiolitis Obliterans?
Bronchiolitis obliterans is also referred to as obliterative bronchiolitis or constrictive bronchiolitis. It’s often labeled as bronchiolitis obliterans syndrome when it happens after a lung transplant or a type of stem cell transplant known as hematopoietic stem cell transplantation. This is a rare lung disease that specifically affects the small airways. It is recognized by the growth of fibrous tissue in the final and remote sections of the bronchioles, the small branches of the airways, as detected by a lung function test called spirometry. The disease often results in a steady decline in lung function and can have a range of consequences.
What Causes Bronchiolitis Obliterans?
A number of risk factors can cause bronchiolitis obliterans, a lung disease. It frequently occurs as a common non-infection related complication after a lung or stem cell transplant. Certain environmental exposures, such as inhaling harmful substances like sulfur mustard gas, nitrogen oxides, diacetyl (used in popcorn flavoring), fly ash, and fiberglass could also lead to this disease.
Bronchiolitis obliterans is also linked to autoimmune disorders like rheumatoid arthritis and SLE (Systemic Lupus Erythematosus), and sometimes with inflammatory bowel disease. This condition can also develop after a severe lung infection caused by viruses like adenovirus or respiratory syncytial virus, which is especially common in children. Other infections that can lead to bronchiolitis obliterans include HIV, mycoplasma, bacteria, fungi, and Human Herpes Virus.
Rare health conditions like Castleman disease and paraneoplastic pemphigus have been found to be related to bronchiolitis obliterans. Additional connections have been found with tiny tumors called ‘microcarcinoid tumorlets’ and an unexplained disease called ‘Cryptogenic constrictive bronchiolitis’.
Risk Factors and Frequency for Bronchiolitis Obliterans
Bronchiolitis obliterans syndrome is a long-term issue that can occur after a lung transplant. It’s categorized as a chronic rejection of the new organ. How common is it? Sadly, many lung transplant recipients who survive for a long time will eventually develop bronchiolitis obliterans syndrome. In fact, over half will start to show signs of the condition within five years of their transplant surgery. On average, it takes between 16 to 20 months to identify the problem after the transplant, but in some cases, it can be detected as soon as 3 months after the procedure.
But it’s not just lung transplant recipients who can develop this syndrome. Between 5% to 14% of people who have received a Hematopoietic stem cell transplant (a specific type of bone marrow transplant) can also get bronchiolitis obliterans syndrome. In these cases, the condition is considered a lung-related aspect of a condition known as graft vs. host disease and it can start to show up several months or even years after the bone marrow transplant.
Signs and Symptoms of Bronchiolitis Obliterans
Bronchiolitis obliterans is a lung condition typically marked by persistent and progressive symptoms such as shortness of breath and coughing. Some people might also experience wheezing. These symptoms usually develop over a span of weeks to months and are constant rather than occurring in episodes like in asthma. A person’s history might also reveal exposure to harmful gases or recent viral infections. Other symptoms can include joint stiffness if they have rheumatoid arthritis or past lung or stem cell transplant.
Upon physical examination, signs may include reduced breath sounds and a prolonged breath out phase that may be accompanied by wheezing during both inhaling and exhaling. Some cases might also present with abnormal crackling sounds upon breathing, known as rales. Bronchiolitis obliterans associated with a condition known as Castleman’s disease may also present with a specific skin condition (paraneoplastic pemphigus) that can cause oral ulcers, as well as swollen lymph nodes.
Testing for Bronchiolitis Obliterans
Testing of lung function is vital when diagnosing certain conditions. One type of test is called Spirometry, which checks how well your lungs work by measuring how much air you breathe in and out and how quickly you do so. This test can reveal if there’s a blockage in your airflow, which doesn’t go away after using an inhaler meant to open up your lungs. A specific measure called FEV1, which is the amount of air you can forcefully blow out in one second, will be found to be lower than the norm. Another measure, called the FEV1/FVC ratio, is also lower than usual. You might also experience inflated lungs, causing an increase in the total lung capacity and trapping more air in your lungs. Another measure called DLCO, which gauges how well your lungs exchange gases, is usually reduced too. The severity of the decline in FEV1 from levels after a lung transplant helps determine the stage of a condition called bronchiolitis obliterans syndrome.
You might also undergo X-rays of your chest. In early stages of certain diseases, the X-ray might appear normal, though it could also reveal inflated lungs. CT scans of the chest could show thickened walls of the airways and an uneven pattern with patches of less dense areas. If the scan includes images taken during inhaling and exhaling, the same pattern could persist due to air becoming trapped due to disease in the small airways.
If there’s a suspicion of other causes of blocked airways like tumors within the airways or a condition called sarcoidosis, you might undergo a procedure called bronchoscopy. However, this procedure might not reveal much in cases of bronchiolitis obliterans. Usually, a lung biopsy, which is a procedure to get a small sample of lung tissue, is not required for diagnosis if symptoms are clear, there’s evidence of air trapping in imaging, lung function tests show blocked airways, and there was either organ transplantation or damaging inhalation exposure in your history. But if a biopsy is necessary, an operation to obtain lung tissue is preferred over a procedure called a transbronchial biopsy, which samples tissue from the bronchi. This is because the disease usually affects the tiny airways rather than the large sections of lung tissue. Also, transbronchial biopsies don’t always correctly diagnose bronchiolitis obliterans. In cases of changes in lung function after a lung transplant, a biopsy might not be needed to diagnose bronchiolitis obliterans syndrome but might be required to rule out other causes like infection or sudden rejection. An obstructive pattern in spirometry, indicating blocked airways, is necessary for diagnosis.
Treatment Options for Bronchiolitis Obliterans
Bronchiolitis obliterans syndrome is a common complication after a lung transplant and is considered to be a type of chronic rejection. To manage this condition, doctors tend to increase medications that suppress the immune system, as they believe the body is rejecting the new organ. The types of medications used include tacrolimus, cyclosporine, mycophenolate mofetil, and prednisone.
Another medication, Azithromycin, has also been found to reduce the chances of developing bronchiolitis obliterans syndrome and improve lung function. A triple therapy treatment, consisting of the inhaled medication fluticasone, the oral drug montelukast, and azithromycin, has also been found to slow the decline in lung function that accompanies this syndrome after a hematopoietic stem cell transplant (a procedure that aims to restore stem cells that have been destroyed by high-dose treatments such as chemotherapy).
Another essential part of treating bronchiolitis obliterans syndrome is controlling gastroesophageal reflux, a condition that exacerbates the symptoms of the syndrome. In severe cases where the syndrome continues to progress and worsen, a patient may need to undergo a lung retransplantation.
Furthermore, a therapy called extracorporeal photopheresis has been successful in slowing the decline in lung function caused by bronchiolitis obliterans syndrome.
For patients with bronchiolitis obliterans that is not related to a transplant, doctors recommend avoiding the factors causing the syndrome. For instance, if it’s caused by rheumatoid arthritis, corticosteroids and cytotoxic agents like cyclophosphamide may be used. However, these treatments have not shown benefits for people with bronchiolitis obliterans caused by toxic inhalation or post-infection. In these cases, symptom management is essential, and this may include cough suppressants, inhaled medications to widen the airways (bronchodilators), and oxygen therapy if required.
What else can Bronchiolitis Obliterans be?
- Asthma
- Lung cancer
- Bronchiectasis (a long-term condition where airways widen and become scarred)
- Cystic fibrosis (an inherited condition that affects the lungs and digestive system)
- Interstitial lung disease (various diseases affecting the tissue and space around the air sacs of the lungs)
- Pleural effusion (fluid build-up in the layers of tissue lining the lungs and chest cavity)
- Pulmonary edema (swelling and fluid build-up in the lungs)
- Recurrent aspiration (when food or liquids are frequently breathed into the lungs)
- Recurrent pulmonary emboli (repeated blood clots in the lungs)
- Tracheobronchomalacia (a condition causing the airway to collapse while breathing out)
What to expect with Bronchiolitis Obliterans
The outcome for individuals with a condition called bronchiolitis obliterans largely depends on the details of their specific situation. Some patients experience total improvement, while those with a certain type of this disease, known as constrictive, typically face a more challenging journey with the illness worsening over time. Right now, we don’t have enough research to back up these observations with concrete statistics.
As the disease progresses, there’s often a decline in lung function, meaning these patients will likely need ongoing lung tests throughout their lives. In severe cases, they may require additional oxygen or a machine to help them breathe. The most serious situations may even necessitate a lung transplant.
Possible Complications When Diagnosed with Bronchiolitis Obliterans
People with a condition called bronchiolitis obliterans have a heightened risk of getting lung infections like bronchitis and pneumonia. In individuals with bronchiolitis obliterans, these infections can turn quite severe, leading to respiratory symptoms that are significantly worse than in persons without this condition.
