Respiratory Bronchiolitis-Associated Interstitial Lung Disease

Abstract

Respiratory bronchiolitis-associated interstitial lung disease (RBILD) can be viewed as an exaggerated respiratory bronchiolitic response to cigarette smoke. The histologic, high-resolution computed tomographic (HRCT) and bronchoalveolar lavage (BAL) features of RBILD overlap substantially with those of respiratory bronchiolitis, with the diagnosis of RBILD being based upon the severity of disease, as judged by symptoms, clinical signs, the severity of lung function impairment, and the extent of abnormalities on HRCT. Typical histologic appearances consist of an accumulation of pigmented macrophages within respiratory bronchioles, associated with peribronchial chronic inflammatory cell infiltration and, variably, peribronchial fibrotic alveolar septal thickening. Characteristic HRCT findings include poorly defined centrilobular micronodules, patchy limited ground-glass attenuation, bronchial wall thickening, and areas of regional hypoattenuation. The ventilatory defect is often mixed but is usually predominantly restrictive. The diagnosis of RBILD is often made on clinical and HRCT criteria, with BAL findings providing useful diagnostic support, but a thoracoscopic biopsy continues to be required when other features are atypical. RBILD may regress with discontinuation of smoking but often persists with no functional improvement despite smoking cessation and treatment. Nonetheless, the course tends to be benign, without inexorable deterioration. This article outlines the rationale for viewing RBILD and desquamative interstitial pneumonia as separate entities, rather than two ends of the same disease spectrum (based upon overlapping histologic and HRCT features).

Mimics in chest disease: interstitial opacities

“…RB-ILD may exhibit moderate to extensive bilateral ground-glass opacities associated with poorly defined centrilobular nodules of ground-glass attenuation [22] (Fig. 13).…”

“…In RB-ILD there is centrilobular or paraseptal emphysema in the upper lobes, which is of mild severity despite the fact that most of the patients are heavy smokers. The differential diagnosis between RBILD and HP is often impossible on imaging grounds only, and the distinction is based on the smoking history as hypersensitivity pneumonitis is uncommon in smokers [22, 55].

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Relationship between gene expression and lung function in Idiopathic Interstitial Pneumonias

“…Idiopathic pulmonary fibrosis (IPF), by far the most common form of IIP, is histopathologically defined by the presence of the prototypical form of pulmonary fibrosis, usual interstitial pneumonia (UIP), a fibrosing interstitial pneumonia characterized by a pattern of heterogeneous, subpleural regions of fibrotic, and remodeled lung that often results in death within 2–3 years of diagnosis [ 4 ]. Other IIPs, such as respiratory bronchiolitis-associated interstitial lung disease (RB-ILD), are more cellular, occur earlier in life, and have a considerably lower mortality [ 5 ]. By contrast, idiopathic nonspecific interstitial pneumonia (iNSIP), a pattern of IIP that is more likely a syndrome than a disease, is most commonly characterized by interstitial fibrosis but in a more uniform pattern than UIP, and carries a better prognosis than IPF/UIP [ 6 , 7 ].…”

Ulcerative colitis combined with acute interstitial lung disease and airway disease: A case report and literature review

“…The pathological features of the case reported in the present study were different from airway-centered fibrosis (with features of inhalation exposure history and bronchial lumen stenosis), cryptogenic organizing pneumonia (with features of granulation tissue or fibrous tissue causing an obstruction in the bronchiole), respiratory bronchiolitis associated with ILD (with pathological features of alveolar macrophage accumulation in the respiratory bronchiole and surrounding alveolus) with mild interstitial inflammation and fibrosis around the bronchioles (22). Therefore, these diseases reported previously could be excluded.…”