Respiratory bronchiolitis is asymptomatic and refers to a histological finding that is almost exclusive to heavy tobacco smokers.
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Pathology
It consists of mild chronic inflammation and accumulation of pigmented macrophages within respiratory bronchioles and related alveoli 1,2. A small amount of fibrosis in the walls of respiratory bronchioles may also be present 2 however these changes are too mild to present with symptoms (by definition).
It is closely related to respiratory bronchiolitis interstitial lung disease (RB-ILD) which represents a more advanced and symptomatic form of the same condition and is also seen almost exclusively amongst smokers. The occurrence of respiratory bronchiolitis in the absence of smoking is extremely uncommon, and its cause is unknown 5. Along the same spectrum of disease is also desquamative interstitial lung disease (DIP) 1 although it is not confined only to smokers.
Radiographic features
Usually respiratory bronchiolitis has no imaging findings, although occasionally minor patchy ground glass opacities and ill-defined centrilobular nodules may be seen, which tend to be more pronounced in the upper zones 2.
History and etymology
It is thought to have been first described by D E Niewoehner et al. in 1974 3,4.
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