Respiratory Bronchiolitis with Interstitial Lung Diseas (RB ILD) is one of the major types of interstitial lung diseases. RB may exist by itself, or it may show ILD, which in turn may or may not show significant fibrosis.


Clinical features:

(1) It is seen primarily in long-term cigarette smokers who are in their 40’s or 50’s.

(2) RB by itself has no or minor symptoms. Development of interstitial lung disease may be associated with pulmonary symptoms and abnormal pulmonary function tests (obstructive and/or restrictive)

(3) It often clinically improves if the person stops smoking.


Histologic features of respiratory bronchiolitis (RB):

(1) There is accumulation of alveolar macrophages in a bronchiolocentric pattern.

(2) The cytoplasm of the macrophages shows a dusty brown material some of which may be positive on an iron stain.

(2) There may be mild bronchiolar fibrosis.

(3) There may be mild bronchiolar inflammation.


Development of ILD is associated with:

(1) thickening of the walls of central and peripheral bronchi

(2) ground-glass opacities

(3) centrilobular nodules


Features suggesting another diagnosis:

(1) diffuse accumulation of macrophages

(2) severe interstitial fibrosis with or without honeycomb change

(3) granulomas

(4) mucus plugging of airways


Some patients may develop interstitial fibrosis with paucicellular lamellar eosinophilic collagenous thickening of alveolar septa in a patchy distribution, typically subpleural. The appearance may resemble amyloid.


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