Abstract
Background: Patients with slowly progressive idiopathic interstitial pneumonia, including idiopathic pulmonary fibrosis, often deteriorate, thus suggesting that the clinical course may be unpredictable. Such episodes are termed acute exacerbation of idiopathic interstitial pneumonia. The etiology of an acute exacerbation of idiopathic interstitial pneumonia is unknown. In this study, we tested the hypothesis that an acute exacerbation of idiopathic interstitial pneumonia is induced by respiratory viral infections. Methods: Bronchoalveolar lavage fluid obtained from patients with an acute exacerbation of idiopathic interstitial pneumonia was tested for viral nucleic acid using polymerase chain reaction. Results: Only 1 of the 14 patients with an acute exacerbation of idiopathic interstitial pneumonia exhibited evidence of respiratory syncytial virus B, and 2 patients exhibited evidence of cytomegalovirus. Seven patients fulfilled the diagnostic criteria of idiopathic pulmonary fibrosis. Conclusions: Most cases with an acute exacerbation of idiopathic interstitial pneumonia are not caused by a viral infection.