Histopathological findings of biopsies from patients with extrinsic allergic alveolitis (hipersensitivity pneumonia) in subacute or chronic phase

Introduction Extrinsic allergic alveolitis (EAA) in chronic phase is a infrequent and a disease difficult to diagnose. Biopsy findings varies and histology is an important tool for diagnosis. We present a series studied in our institution. Method We revised the pathology registries at Instituto Nacional del Torax, Santiago, Chile, between 2005 and 2009. We identified patients with surgical biopsy compatible with EAA. The demographic and clinical information was obtained from hospital medical records. Surgical biopsies were reviewed in detail by one of the authors specifying the presence of: usual interstitial pneumonia areas (UIP), nonspecific interstitial pneumonia areas (NSIP), subacute hypersensitivity areas and presence of granuloma, Masson bodies (CM), Schaumann bodies (CS), fibroblastic foci (FF) and distribution around the airway. We consider lymphocytosis on broncoalveolar lavage when lymphocytes count is over 30 %. Results There were a total of 37 cases, 27 women (73%) and average 57 years of age. Ninety seven percent had granulomas on biopsy, 97 % had subacute hypersensitivity areas and 94.5% had distribution around the airway. Forty percent had areas of UIP, 51% areas of NSIP and 46% presence of fibroblastic foci. CM was found in 33% and CS in 19%. Fifteen patients had bronchoalveolar lavage; seven of them (46%) lymphocytosis presented with found. Conclusions Even though, the most consistent histological findings of biopsies from patients with chronic phase AAE, are the presence of granulomas and areas of subacute hypersensitivity pneumonia, there are a number of other finding that could be present.