ABSTRACT
I. Introduction Although lung transplantation improves survival and provides significant short-term improvements in quality of life for patients with advanced lung diseases, five-year survival following transplantation is limited to 50% with most late deaths due directly or indirectly to the development of bronchiolitis obliterans syndrome (BOS) (1). BOS describes a condition of progressive airflow obstruction associated with chronic airway fibrosis, a pathologic finding known as bronchiolitis obliterans (BO) (Fig. 1). Transplant physicians first recognized this progressive airflow obstruction and associated BO in early lung or heart-lung transplant recipients (1). Unfortunately, transbronchial biopsies, routinely performed to diagnose acute rejection (AR) and infection after lung transplantation, are insensitive for the identification of BO because of the limited sampling of bronchiolar tissue and the disease’s heterogeneous nature. The clinical syndrome of BOS was thus developed to identify patients with underlying BO. BOS is diagnosed by a persistent fall from a patient’s baseline post-transplant forced expired volume in one second (FEV1) after the exclusion of other causes of airflow obstruction. Current treatment modalities are generally ineffective in arresting airflow decline, so BOS patients steadily progress toward pulmonary failure and death unless retransplanted.
