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A1691 - Idiopathic Pulmonary Fibrosis in Never Smokers
Author Block: M. Toyoshima1, A. Fukada1, D. Akahori1, T. Suda2; 1Department of Respiratory Medicine, Hamamatsu Rosai Hosp, Hamamatsu, Japan, 22nd Div Dept of Internal Medicine, Hamamatsu 431 3192, Japan.
Rationale: Several previous studies demonstrated the possible involvement of smoking in the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, we often encounter IPF patients who had never smoked. To investigate the characteristic features of IPF in never smokers, we conducted a retrospective study. Methods: To exclude the influence of emphysema on clinical features of IPF, this study included only IPF patients with high resolution computed tomography (HRCT) findings of definite usual interstitial pneumonia patterns without obvious emphysema. Results: A review of medical records identified 39 IPF patients without emphysema on HRCT. Fifteen of 39 IPF patients had never smoked. In IPF patients who had never smoked, more female patients were included than in those who had smoked (73.3% vs. 0.0%, p=0.017). Patients with IPF who had smoked had significantly lower %FEV1 (94.4% vs. 112.3%, p=0.014), %DLco/VA (73.3% vs. 94.4%, p=0.004), and higher %RV (107.2% vs. 80.0%, p=0.005) than patients with IPF who had never smoked. MPO-ANCA was more frequently positive in patients with IPF who had never smoked than in patients with IPF who had smoked (27% vs. 0%, p=0.009). There were no significant differences in other laboratory findings including autoantibodies except MPO-ANCA. There were no significant differences in frequency of acute exacerbation (27% vs. 29%, p=0.882) and mortality rate from IPF-related conditions (27% vs. 42%, p=0.497) such as acute exacerbation, chronic respiratory failure and lung cancer in both groups with mean observation periods of 31 months in patients with IPF who had never smoked and 45 months in in patients with IPF who had smoked (p=0.686). . Conclusions: Clinical features of IPF in never smokers were not different from those of IPF in smokers except for female predominance and more frequent MPO-ANCA positivity in IPF in never smokers. Based on these results, smoking appears to not be directly related to the pathogenesis of IPF, although it can alter clinical features of IPF via development of emphysema, as reported in previous studies in combined pulmonary fibrosis and emphysema and some patients with IPF who had never smoked might be considered as interstitial pneumonia with autoimmune features. The limitation of this study is a single center study involving small numbers of patients, and further investigations involving larger numbers of patients will be needed to clarify the role of smoking status in pathophysiology of IPF.