Desquamative interstitial pneumonia and respiratory bronchiolitis-associated interstitial lung disease

Background: Desquamative interstitial pneumonia (DIP) and respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) are uncommon forms of interstitial lung disease and have been incompletely characterized. Study objectives: To further characterize the clinical features and course of subjects with DIP and RB-ILD. Design: Retrospective study. Setting: Tertiary care, referral medical center. Patients: Twenty-three subjects with DIP and 12 subjects with RB-ILD seen over a 12-year period between 1990 and 2001. Interventions: None. Results: The study population included 19 men (54%) and 16 women (46%). The mean (+/- SD) age at diagnosis was 46 +/- 10 and 43 +/- 7 years, respectively, for patients with DIP and RB-ILD. All subjects were either current or previous smokers except for three subjects with DIP. The diagnosis was confirmed in all cases by surgical lung biopsy. Bronchoscopy with transbronchial lung biopsy had been performed in 12 patients and was nondiagnostic in all. The most common pulmonary function abnormality was a reduced diffusing capacity of the lung for carbon monoxide. A CT scan of the chest revealed ground-glass opacities bilaterally in most patients who had DIP and RB-ILD. No differences were observed between subjects with DIP and RB-ILD with respect to clinical features, radiologic findings, or pulmonary function test results. The clinical course was characterized by relative stability in the majority of patients in both groups and a partial response to corticosteroid therapy. Five deaths were observed, including three resulting from progressive diffuse lung disease, all in subjects with DIP. Conclusions: We concluded that DIP and RB-ILD are chronic disease processes that in most patients are related to smoking. Persistent abnormalities can be seen on pulmonary function testing and radiologic studies despite smoking cessation and corticosteroid therapy. Corticosteroid therapy appeared to be associated with modest clinical benefit but usually not with resolution of disease. Progressive disease with eventual death can occur in subjects with DIP, especially with continued cigarette smoking.