ICD-11

Bronchiolitis and bronchiolitis obliterans are general terms used to describe a nonspecific inflammatory injury that primarily affects the small airways and generally spares the interstitium. Bronchiolitis may be caused by inhalation injury, infection, or drugs; associated with organ transplantation or connective tissue disease; or may be idiopathic. The main pathologic categories of bronchiolitis are: constrictive, proliferative, follicular, airway-centred interstitial fibrosis, and diffuse panbronchiolitis. The constrictive and proliferative patterns may occur together.

Bronchiolitis obliterans is commonly used to describe a number of unrelated conditions whose common end point is functional obstruction of bronchioles. A typical form is constrictive bronchiolitis. Constrictive bronchiolitis is an uncommon histologic finding characterised by alterations in the walls of membranous and respiratory bronchioles, often without extensive changes in alveolar ducts and alveolar walls. These changes lead to concentric narrowing or complete obliteration of the airway lumen. The clinical manifestations of constrictive bronchiolitis usually include progressive airflow obstruction, sometimes in the presence of a relatively normal chest radiograph. The clinical severity depends upon the type, extent, and severity of the initial lung injury.