American Thoracic Society/European Respiratory Society classification of idiopathic interstitial pneumonias (2013): Multidisciplinary diagnoses

* Causes of unclassifiable idiopathic interstitial pneumonia include (1) inadequate clinical, radiologic, or pathologic data and (2) major discordance between clinical, radiologic, and pathologic findings that may occur in the following situations: (a) previous therapy resulting in substantial alteration of radiologic or histologic findings (eg, biopsy of desquamative interstitial pneumonia after glucocorticoid therapy, which shows only residual nonspecific interstitial pneumonia^[1]); (b) new entity, or unusual variant of recognized entity, not adequately characterized by the current American Thoracic Society/European Respiratory Society classification (eg, variant of organizing pneumonia with supervening fibrosis)^[2]; and (c) multiple high-resolution computed tomography and/or pathologic patterns that may be encountered in patients with idiopathic interstitial pneumonia.