Histological variability and consequences in chronic bird‐related hypersensitivity pneumonitis

Background and objective Lobar and temporal histological variability in chronic bird‐related hypersensitivity pneumonitis ( BRHP ) has not been clearly elucidated. This study was designed to evaluate the spatio‐temporal histopathological variability in chronic BRHP . Methods Fifty‐two patients with chronic BRHP who underwent a surgical lung biopsy ( SLB ) between 1992 and 2008 were evaluated. The histopathological characteristics of the lung biopsy specimens were classified by the 2002 American Thoracic Society/European Respiratory Society ( ATS / ERS ) consensus classification of idiopathic interstitial pneumonias ( IIPs ). Autopsy specimens from seven patients were also evaluated to examine the serial changes from SLB to autopsy. Results In a study of lobar histological variability based on the findings of SLB , 7 patients were diagnosed with cellular nonspecific interstitial pneumonia ( NSIP ) pattern, 16 with fibrotic NSIP pattern, 20 with fibrotic NSIP pattern and usual interstitial pneumonia ( UIP ) (discordant UIP ) pattern and 9 with UIP (concordant UIP ) pattern. In a study of sequential changes, specimens of SLBs with fibrotic NSIP pattern changed to a bronchiolocentric interstitial pneumonia ( BIP ) pattern or UIP pattern. Conclusion Interlobar and intralobar histological variability is present in chronic BRHP . In several patients with chronic BRHP , a fibrotic NSIP pattern may be an early lesion that progresses to a UIP pattern.