What is Bronchiolitis Obliterans Syndrome (BOS)?
BOS is a lung problem that can occur after lung transplantation and is the most common form of chronic lung transplant rejection. More than half of lung transplant recipients develop BOS within five years of transplantation. When BOS develops, a person will have a progressive loss of lung function when compared to the highest function after transplantation.
Although the initial symptoms may sometimes mimic those seen from a lung infection, BOS is not due to infection. The main change seen with BOS is scarring of the small airways of the transplanted lung(s). This scarring leads to the narrowing of the airways, limiting airflow with loss of lung function. Early after the onset of BOS, a person may not have any symptoms but will develop breathlessness and chronic cough as BOS gets worse. There are different stages of BOS based on lung function results. Some people develop an early stage of BOS and progress to more severe stages over a short time period, while others may remain stable in a stage for an extended period of time. There is no clear way to predict the course of BOS over time for a given person.
Recently, the Lung Transplant Foundation hosted a Patient-Focused Drug Development meeting with the FDA. During the meeting, caregivers and people living with BOS shared their personal stories to unite the community and create hope.