Chronic Hypersensitivity Pneumonitis With a Usual Interstitial Pneumonia-Like Pattern: Correlation Between Histopathologic and Clinical Findings

Background Hypersensitivity pneumonitis (HP) is an interstitial lung disease caused by the inhalation of environmental antigens. The relationship between clinical, radiologic, and histopathologic findings of chronic HP remains unclear. Methods Sixteen patients with proven chronic bird-related HP with a usual interstitial pneumonia-like pattern were analyzed retrospectively. Histopathologic findings were semiquantitatively assessed and compared with clinical and radiologic findings. We also evaluated the histopathologic findings affecting prognosis. Results The extent of centrilobular fibrosis was negatively correlated with Pa o 2 ( r  = –0.55, P  = .03). The extent of bridging fibrosis was positively correlated with the ratio of maximal expiratory flow at 50% of forced vital capacity to that at 25% ( r  = 0.60, P  = .02). Patients with a greater extent of fibroblastic foci (FF) had more radiologic reticulation ( P  = .01), honeycombing ( P  = .01), and traction bronchiectasis ( P  = .02), and had significantly shorter survival time ( P  = .01) than patients with a lesser extent of FF. Multivariate analysis showed that the extent of FF was a significant prognostic factor (hazard ratio, 2.36; 95% confidence interval, 1.02-5.48; P  = .04). Conclusions Our findings demonstrated that the extent of FF was significantly associated with reticulation, honeycombing, and traction bronchiectasis on high-resolution CT scanning. Moreover, the extent of FF could be a useful predictor of mortality in chronic HP with a usual interstitial pneumonia-like pattern.