by What is Bronchiolitis Obliterans Syndrome?
Bronchiolitis obliterans syndrome (BOS), also known as obliterative bronchiolitis (OB), is a chronic lung disease characterized by inflammation and fibrosis in the small airways of the lungs, leading to airflow limitation. It commonly occurs in lung transplant recipients as a late complication, but can also develop from other causes such as toxic exposures.
Symptoms of BOS
The main symptom of BOS is shortness of breath, also known as dyspnea. The dyspnea worsens with exertion and may limit a person’s ability to perform daily activities. Other common symptoms include a dry cough, fatigue, and low-grade fever. As the disease progresses, dyspnea at rest may develop. Symptoms typically arise months to years after lung transplantation or other inciting events such as toxic inhalation.
Causes and Risk Factors
In lung transplant recipients, BOS is considered a form of chronic lung allograft dysfunction caused by rejection of the donor lung. Risk factors for developing BOS after transplantation include primary graft dysfunction, repeated acute rejection episodes, cytomegalovirus infection, and noncompliance with the immunosuppression regimen.
Other potential causes of BOS include toxic inhalation from chemicals like nitrogen mustard, chlorine gas, or ammonia. It has also been reported following bone marrow or stem cell transplantation. A small subset of patients develop idiopathic BOS of unknown cause.
Diagnosis of Bronchiolitis Obliterans Syndrome
There is no single test to diagnose BOS. Physicians rely on a combination of clinical features, pulmonary function tests, imaging studies, and exclusion of other lung diseases.
Pulmonary function tests typically show a gradual decline in forced expiratory volume in 1 second (FEV1) over time compared to previous tests. A drop of ≥20% in FEV1 from baseline on two consecutive tests is one criterion used to diagnose BOS.
Chest imaging with CT scans may show decreased attenuation of the lungs, suggesting air trapping. Lung biopsies in lung transplant patients often reveal various degrees of obliteration of the small airways by fibrotic tissue.
Treatment and Prognosis
There is no cure for Bronchiolitis Obliterans Syndrome once established. Treatment focuses on slowing disease progression and managing symptoms. Immunosuppression medications are frequently adjusted or changed in lung transplant patients. Other therapeutic options include bronchodilators, oxygen therapy, pulmonary rehabilitation, and lung volume reduction surgery in select patients.
The five-year survival rate for lung transplant recipients who develop Bronchiolitis obliterans syndrome is around 40-50%, depending on severity. Progression to complete lung allograft failure occurs in approximately half of BOS patients over time. Early diagnosis and treatment provide the best outcomes. However, BOS remains a serious complication that often leads to re-transplantation or death for many individuals.
A bronchiolitis obliterans syndrome is a pulmonary disease characterized by small airway fibrosis and obstruction. It commonly affects lung transplant recipients as a complication caused by alloimmunity and chronic rejection. Diagnosis relies on classic clinical features along with pulmonary function and imaging testing. Treatment focuses on slowing disease progression, but BOS carries a significant mortality risk over the long term in many affected individuals. Further research aims to better understand the immunopathogenesis of BOS and develop more effective prevention and treatment strategies.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
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