What is the difference between bronchiolitis obliterans (BO) and bronchiolitis obliterans organizing pneumonia (BOOP)?
BO is generally a disease of the small airways, where the small airways become narrower presumably due to GVHD, to the point that airflow is limited through the airways. On lung function testing, this appears as an obstructive pattern. When detected, BO is usually severe and generally irreversible. The goal of therapy with immunosuppression is to prevent progression. Unfortunately, BO is often “silent” and clinically unnoticed until it is severe. BO is generally not detectable using standard chest X-ray or CT, but can be detected using a high resolution CT scan. Respiratory infections can also cause airflow obstruction, so patients generally need a bronchoscopy to make sure an infection is not present before initiation of therapy. Therefore, our efforts here have focused on how to identify patients earlier, so treatment may be started to stop the progression of BO before it becomes severe. BOOP is an inflammatory disease that involves the small airways and the alveoli, the gas exchangi