Respiratory bronchiolitis with fibrosis: a form of smoking-related disease

Abstract

A new smoking-associated lesion has been described in the pathology literature over the last few years by various names including RBILD with fibrosis, smoking-related interstitial fibrosis, and airspace enlargement with fibrosis. The lesion consists of localized patches of paucicelluar interstitial fibrosis mixed with emphysema, and frequently forms a wedge shape under the pleura. We recently proposed that this lesion be called respiratory bronchiolitis with fibrosis (RBF) and showed that in at least some cases RBF has a distinctive high resolution CT (HRCT) appearance consisting of sharply circumscribed patches of subpleural reticulation mixed with emphysema. In an HRCT survey of heavy smokers we found this lesion in 5% of patients; but it is much more frequent in pathology specimens from heavy smokers. RBF, like smokers respiratory bronchiolitis, generally produces no symptoms and no demonstrable physiologic impairment, but in a fashion analogous to RBILD, a small fraction of patients have evidence of a mild interstitial lung disease which we suggest be called RBF-ILD. This lesion is often mistaken pathologically and radiologically for a diffuse fibrosing interstitial lung disease, but RBF-ILD is nonprogressive and does not evolve into a more serious form of interstitial lung disease.