Obliterative bronchiolitis (OB), also known as bronchiolitis obliterans, is a rare but serious condition resulting in progressive and irreversible airway obstruction. This disease is the result of injury to the respiratory and terminal bronchioles from a wide variety of potential causes. Although the pathogenesis of OB remains poorly understood, it seems clear that a multifaceted process of inflammation and resultant fibrotic transition occurs, resulting in airflow limitation and development of disease. Although OB has been described in all age groups, the frequency of underlying causes and potential prognoses are different for children and adults. For example, OB in children is most often seen following a severe lower-respiratory-tract infection, usually of adenovirus, whereas OB in adults is more commonly associated with occupational inhalation injuries, hypersensitivity pneumonitis, and autoimmune disorders. In lung transplant recipients, bronchiolitis obliterans syndrome is the major cause of death after the first year of transplantation and is a form of allograft rejection. There is no uniformly accepted treatment protocol for patients with OB. Many patients are tried on corticosteroids or other immunosuppressants based on anecdotal evidence of improvement. However, these medications have significant toxicity.
In the present manuscript, the following terminology is used: "bronchiolitis obliterans" (historically used for the histopathological lesions) to name the pathological feature of reduced lumen of the bronchioles, and "obliterative bronchiolitis" (OB) to name its functional counterpart with airflow obstruction.
