Respiratory bronchiolitis (RB) and respiratory bronchiolitis–associated interstitial lung disease (RB-ILD) are 2 processes that lie along the continuum of probable smoking related lung diseases. The separation of the 2 is difficult and sometimes contentious; however, the combination of clinical symptoms and suggestive pathologic findings usually allows for a distinction and the subsequent diagnosis.
RB in an asymptomatic smoker is considered an incidental histologic finding consistent with prior tobacco history. RB-ILD, although histopathologically similar to RB, is characterized by more extensive pulmonary parenchymal involvement and clinical expression as defined by dyspnea or other respiratory complaints. On pulmonary function testing, RB-ILD patients often demonstrate a mixed picture of obstructive or restrictive physiology, in combination with a reduced carbon monoxide diffusion capacity. Plain chest radiography is of limited utility and can be normal in many RB-ILD patients. High-resolution computer-assisted tomography scanning in the setting of RB-ILD correlates with the extent of bronchiolitis on pathologic analysis and offers a potential role for assessing response to therapy. Thus far, bronchoscopy has demonstrated a relatively limited capacity in diagnosing RB-ILD, necessitating surgical lung biopsy to arrive at a definitive diagnosis. Treatment of RB-ILD hinges upon smoking cessation maneuvers and consideration of immunosuppressive agents in recalcitrant cases.