[Clinicopathological diagnosis of hypersensitivity pneumonitis]

To enhance the understandings of clinical, radiological and pathological features of hypersensitivity pneumonitis (HP).

Six HP cases with pathological data, clinical and radiological data were retrospectively analyzed during the period from February 2009 to September 2011 at Beijing Hospital of Ministry of Health. There were 2 males and 4 females with a mean age of 51.5 years (range: 38-61). Clinically, the patients presented with chronic cough, shortness of breath and dyspnea (n = 2). The disease course was 1-8 months. Five cases had fed pigeons and other contact histories. Specimens obtained by transbronchial lung biopsy (n = 3) and open lung biopsy (n = 3) were paraffin embedded and stained by hematoxylin and eosin, special stains and immunohistochemistry.

Four cases had subacute HP and 2 cases chronic HP. Three cases of subacute HP underwent transbronchial lung biopsy. One case of subacute HP and 2 cases of chronic HP were diagnosed by open lung biopsy. High-resolution computed tomography of lungs showed diffuse ground glass and patch shadow along the bronchial and centrilobular distributions. There was a predominance of upper half zone. Typical visible mosaic syndrome was present. There was poorly formed granuloma without cheesy necrosis. With an insidious medical history and complicated radiological features, chronic HP cases were characterized by pulmonary interstitial fibrosis. There were usual interstitial pneumonitis (UIP)-like fibrosis and fibrosis with an airway-centered distribution type. The lesions were distributed around bronchioles. Continuous bridge fibrosis might be present. There were bronchiolar metaplasia of peribronchiolar alveoli, poorly formed granuloma and multinucleated giant cells in interstitium. Schaumann body was identified in 1 case.

Because of its diverse clinical, radiological and pathological features, HP may be easily confused with other interstitial lung diseases. Aggregate analyses yield a definite diagnosis.