Bronchiolitis is injury to the bronchioles (small airways with a diameter of 2 mm or less)
resulting in inflammation and/or fibrosis. Bronchioles can be involved in pathologic
processes that involve predominantly the lung parenchyma or large airways, but, in some
diseases, bronchioles are the main site of injury (“primary bronchiolitis”). Acute bronchiolitis
caused by viruses is responsible for most cases of bronchiolitis in infants and children. In
adults, however, there is a wide spectrum of bronchiolar disorders and most are chronic …