Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD)

Abstract

Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) designates interstitial lung changes in smokers, characterized histologically by bronchiolocentric accumulation of pigmented alveolar macrophages and fibrotic or cellular inflammatory changes of pulmonary interstitium. The definition is nearly identical to that of condensate pneumopathy, smoker's pneumopathy or smoker's lung, defined by accumulation of pigmented alveolar macrophages with bland alveoloseptal or peribronchial fibrosis and cellular inflammation of the bronchial wall. In addition to respiratory bronchiolitis, which is found in nearly all smokers, RB-ILD comprises a broad spectrum of varying degrees of the interstitial reaction to the exogenous injury of inhalation smoking with gradual transition to desquamative interstitial pneumonia (DIP). In most cases RB-ILD manifestations are subclinical and detected coincidentally. Radiographic features are reticulonodular and ground glass opacities of the lung. The high resolution computed tomography reveals centrilobular nodules, ground glass opacities, thickening of bronchial walls, and in some cases a reticular pattern. Mild emphysema is frequent. Lung function analysis reveals only minor restrictive or obstructive defects in most cases, often combined with hyperinflation. CO diffusing capacity is slightly to moderately impaired. Pronounced interstitial lung diseases with serious restrictive defects and arterial hypoxemia have been reported infrequently. In differential diagnosis smoking related interstitial lung diseases (DIP, Langerhans cell histiocytosis, idiopathic pulmonary fibrosis) and other interstitial lung diseases have to be excluded. In most cases diagnosis can be achieved by bronchoalveolar lavage and transbronchial lung biopsy. In cases of pronounced interstitial lung disease or assumption of an additional interstitial lung disease besides RB-ILD a thoracoscopic or open lung biopsy can be necessary. RB-ILD has a favourable prognosis. After smoking cessation lung changes are reversible. Corticosteroid therapy is not necessary. A fatal outcome of RB-ILD has not been reported. Follow-up examinations are advisable in order to preclude other interstitial lung diseases. RB-ILD seems to be more frequent than it is assumed at present. The clinical picture is masked in most cases by the concomitant smoking induced chronic bronchitis. Thus only pronounced cases with structural changes and resulting differential diagnostic problems are diagnosed.