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For further information, see CMDT Part 9-11: Bronchiolitis
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Essentials of Diagnosis
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Insidious onset of cough and dyspnea
Irreversible airflow obstruction on pulmonary function tests
Minimal findings on chest radiograph, heterogeneous airflow obstruction, air trapping on chest CT scan
Relevant exposure or risk factors
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General Considerations
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Bronchiolitis is a generic term applied to varied inflammatory processes that affect the bronchioles
Bronchiolitis is more common in children than in adults and is usually caused by
Bronchiolitis is encountered in multiple clinical settings
Post-infectious
Inhalational injury (such as vaping)
Organ transplantation
Connective tissue diseases
Hypersensitivity pneumonitis
Idiopathic cases are characterized by the insidious onset of dyspnea or cough
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Classification and Histopathologic Findings
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Constrictive bronchiolitis
Proliferative bronchiolitis
Also called "organizing pneumonia"
Occurs when there is an organizing intraluminal exudate, consisting of fibroblasts, lipid laden ("foamy") macrophages, and other cells that obstruct the bronchiolar lumen
These findings are more common than the constrictive pattern
Associated with diverse pulmonary disorders, including
Infection
Aspiration
Acute respiratory distress syndrome (ARDS)
Hypersensitivity pneumonitis
Connective tissue diseases
Organ transplantation
Follicular bronchiolitis
Characterized by chronic peribronchiolar inflammation and hyperplastic lymphoid follicles with reactive germinal centers arising from bronchus-associated lymphoid tissue (BALT)
Most commonly associated with connective tissue disease, especially
Respiratory bronchiolitis
Affects small airways in cigarette smokers
Characterized by accumulation of pigmented alveolar macrophages within respiratory bronchioles, associated with mild interstitial fibrosis and chronic inflammation
In some patients, however, respiratory bronchiolitis causes diffuse parenchymal infiltrates
This syndrome is referred to as respiratory bronchiolitis–associated interstitial lung disease (RB-ILD)
It is considered to represent part of the spectrum of the smoking-related interstitial lung diseases
Diffuse panbronchiolitis
An idiopathic disorder of respiratory bronchioles
Characterized by a peribronchiolar mixed inflammatory cell infiltrate and accumulation of lipid laden ("foamy") macrophages within the interstitium and alveolar spaces
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Diffuse panbronchiolitis
Most frequently diagnosed in Japan
Men are affected about twice as often as women
Only one-third are smokers
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Constrictive bronchiolitis: progressive, deteriorating clinical course
Follicular bronchiolitis: may be seen in lymphoid interstitial pneumonia
Respiratory bronchiolitis
Most common form of bronchiolitis in adults
Usually related to cigarette smoking
Usually asymptomatic
Usually occurs without physiologic ...