Miscellaneous causes of bronchiolitis: inhalational, infectious, drug-induced, and idiopathic.

Bronchiolitis is increasingly recognized as an important clinical syndrome that encompasses the broad spectrum of histopathologic processes which show some degree of inflammation, narrowing, or obliteration of the small conducting airways. It has an extremely variable clinical course, etiology, and histologic appearance. Understanding of this entity has been limited because until recently only case reports described this lesion in several diverse clinical settings. In addition, there has been considerable confusion as a result of the different terminologies applied to the many syndromes. This article reviews the clinical, radiographic, and histopathologic findings of the bronchiolar syndromes that are secondary to inhalation of chemicals or organic dust, that are secondary to infection, that are drug-induced, and that have no known etiology (idiopathic).