Acute bronchiolitis can be seen following viral infections.
Constrictive bronchiolitis (also referred to as obliterative bronchiolitis, or bronchiolitis obliterans) is relatively infrequent, although it is the most common finding following inhalation injury. It may also be seen in rheumatoid arthritis; medication reactions; and chronic rejection following heart-lung, lung, or bone marrow transplant. Patients with constrictive bronchiolitis have airflow obstruction and air trapping on spirometry, unremarkable plain chest radiographs but heterogeneous airflow obstruction and air trapping on chest CT scans, and a progressive, deteriorating clinical course.
Proliferative bronchiolitis is associated with diverse pulmonary disorders, including infection, aspiration, ARDS, hypersensitivity pneumonitis, connective tissue diseases, and organ transplantation. Compared with constrictive bronchiolitis, proliferative bronchiolitis is more likely to have an abnormal chest radiograph.
Cryptogenic organizing pneumonitis (COP) affects men and women between the ages of 50 and 70 years, typically with a dry cough, dyspnea, and constitutional symptoms that may be present for weeks to months prior to seeking medical attention. A history of a preceding viral illness is present in half of cases. Pulmonary function testing typically reveals a restrictive ventilatory defect and impaired oxygenation. The chest radiograph frequently shows bilateral patchy, ground-glass or alveolar infiltrates, although other patterns have been described.
Follicular bronchiolitis is most commonly associated with connective tissue disease, especially rheumatoid arthritis and Sjögren syndrome, and with immunodeficiency states.
Respiratory bronchiolitis usually occurs without symptoms or physiologic evidence of lung impairment.
Diffuse panbronchiolitis is most frequently diagnosed in Japan. Men are affected about twice as often as women, two-thirds are nonsmokers, and most patients have a history of chronic pansinusitis. Patients complain of dyspnea, cough, and sputum production, and chest examination shows crackles and rhonchi. Pulmonary function tests reveal obstructive abnormalities, and the chest radiograph shows a distinct pattern of diffuse, small, nodular shadows with hyperinflation.