Histopathological patterns on lung biopsy is the primary mode of classifying patients into the various categories defined in the International Consensus Statement. There are 3 techniques for obtaining lung tissue for pathologic analysis. An open lung biopsy provides the most tissue for analysis, a vidio-assisted thoracoscopic (VATS) technique may also provide the tissue needed to make a diagnosis of usual interstitial pneumonia (UIP) and has less morbidity. A transbronchial biopsy is the third technique which may be adequate for certain diagnoses but is not helpful in making a diagnosis of UIP. It is important to accurately diagnose patients with a histopathologic pattern since the inflammatory response of these patterns determines the rate of fibrosis and destruction to the lung. Interstitial lung disease associated with an organic antigen causation may be arrested, or rendered non-progressive, by an aggressive approach to investigation of the home and workplace environment. Other common interstitial diseases including those associated with autoimmune diseases and sarcoidosis have not been recognized to be caused by organic antigens.

Listed are the types of interstitial lung diseases that fit into the major category idiopathic interstitial pneumonia/fibrosis (IIP/F) as defined by the International Consensus Statement. We have also included hypersensitivity pneumonitis, which is not considered of unknown cause, along with chronic eosinophilic pneumonia and pulmonary infiltrate with eosinophilia which we feel are members of this grouping. Sarcoid is included because of similarity to these disorders.

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