Lung biopsy-proved hypersensitivity pneumonitis without known offending antigen: characteristics and follow-up

Hypersensitivity pneumonitis (HP) without known offending antigen is hard to diagnose.

The purpose of this study was to identify and analyze the clinical features of lung biopsy-proved HP.

A retrospective cohort study was performed using a database from a 900-bed specialty hospital. Twenty-eight patients with the diagnosis of HP through lung biopsy were enrolled. Demographic data and clinical characteristics, radiologic characteristics, serologic and pulmonary function results, histopathologic changes, treatment and follow-up were analyzed.

Of all the patients, serum interleukin-1β, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), eosinophil cationic protein and immunoglobulin E (IgE) were increased in over 50% patients, but decreased significantly after corticosteroid therapy (P < 0.05). An initially reduced diffusion lung capacity for carbon monoxide was noted in 92.9% patients, while 39.3% patients had hypoxemia. Ground-glass opacities on the basis of interlobular septa thickening were observed in 71.4% cases. Histopathological findings demonstrated peribronchiolar lymphocytic infiltrates, poorly formed non-caseating granulomas fibrosis in all acute and subacute HP patients' lungs. Ninety-two percent of patients got improvement after corticosteroid therapy when assessed by computer tomography scans and pulmonary function tests.

For suspected HP patients who without known offending antigens, earlier diagnosed by lung biopsy and followed by corticosteroid therapy showed promising. It might prevent the disease progression to lung fibrosis.