The Overlap Between Respiratory Bronchiolitis and Desquamative Interstitial Pneumonia in Pulmonary Langerhans Cell Histiocytosis: High-Resolution CT, Histologic, and Functional Correlations

Abstract

To characterize the histologic, high-resolution CT (HRCT), and functional correlates of respiratory bronchiolitis (RB)/desquamative interstitial pneumonia (DIP)-like changes in biopsy specimens of adults with pulmonary Langerhans cell histiocytosis (PLCH). We retrospectively identified 14 adult patients with histologically proven PLCH (all smokers) in whom both biopsy specimens and HRCT were available for review. The presence and extent of RB/DIP-like changes on lung biopsy specimens of patients with PLCH were correlated with total pack-years of smoking, lung function variables, and the presence of ground-glass attenuation on HRCT. Varying degrees of RB/DIP-like changes were identified in all biopsy specimens. The extent of involvement with RB/DIP-like changes correlated with the cumulative exposure to cigarettes smoked at the time of biopsy (r = 0.61, p = 0.03). Ground-glass attenuation was detected in three HRCTs, two of which had extensive RB/DIP-like changes (> or = 70% involvement) on histology, suggesting that substantial smoking-induced RB/DIP-like changes may be the cause of ground-glass attenuation on the HRCT of patients with PLCH. No correlation was found between the extent of RB/DIP-like changes and total lung capacity, FEV(1), or diffusion capacity of the lung for carbon monoxide. RB/DIP-like changes are exceedingly common in PLCH, may be sufficiently severe to cause the appearance of ground-glass attenuation on HRCT, and correlate with the cumulative exposure to cigarettes smoked. This study provides additional evidence that PLCH, RB, and DIP form a spectrum of interstitial patterns of lung injury to cigarette smoke.