Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) is a type of idiopathic interstitial pneumonia (IIP) that has pathologic features of respiratory bronchiolitis (RB). The other IIPs include idiopathic pulmonary fibrosis (IPF), nonspecific interstitial pneumonia (NSIP), desquamative interstitial pneumonia (DIP), acute interstitial pneumonia (AIP), lymphocytic interstitial pneumonia (LIP), and cryptogenic organizing pneumonia (COP).
The clinical presentation, diagnosis, treatment, and prognosis of RB-ILD will be reviewed here. The evaluation and diagnosis of interstitial lung disease, including the idiopathic interstitial pneumonias, and bronchiolitis are discussed separately. (See "Idiopathic interstitial pneumonias: Clinical manifestations and pathology" and "Approach to the adult with interstitial lung disease: Clinical evaluation" and "Approach to the adult with interstitial lung disease: Diagnostic testing" and "Nonspecific interstitial pneumonia" and "Acute interstitial pneumonia (Hamman-Rich syndrome)" and "Lymphoid interstitial pneumonia in adults" and "Cryptogenic organizing pneumonia" and "Bronchiolitis in adults".)
Respiratory (or "smoker's") bronchiolitis (RB) is a well-recognized pathological lesion found in the lungs of many cigarette smokers that is generally not associated with respiratory symptoms. The key features of RB are the pathologic findings of tan-pigmented macrophages (also known as smokers’ macrophages) in the respiratory bronchioles, a patchy submucosal and peribronchiolar infiltrate of lymphocytes and histiocytes, and peribronchiolar fibrosis that extends into contiguous alveolar walls. (See 'Histopathology' below.)
Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) is defined by the presence of changes of RB as the sole pathologic finding in a current or former cigarette smoker with clinical evidence of interstitial lung disease [1-7]. The degree to which fibrosis extends into the alveolar wall has sometimes been used to distinguish RB from RB-ILD, but most pathologists believe that the two processes cannot be distinguished on pathologic grounds alone [1,8-11]. Thus, RB-ILD probably represents a subset of individuals with a more severe stage in the spectrum of RB and is much less common than RB.
RB is a common finding among smokers, but RB-ILD is uncommon. As an example, in a series of 79 smokers with spontaneous pneumothorax requiring surgical intervention, RB was found in 89 percent of the lung biopsies . Although the exact incidence of RB-ILD is not known, in a review of 168 lung biopsies performed for suspicion of idiopathic pulmonary fibrosis, 10 were RB-ILD . (See 'Histopathology' below and "Idiopathic interstitial pneumonias: Clinical manifestations and pathology".)