Subacute and chronic bird breeder hypersensitivity pneumonitis: sequential evaluation with CT and correlation with lung function tests and bronchoalveolar lavage.

To evaluate lung involvement in the subacute (group 1) and chronic (group 2) stages of bird breeder hypersensitivity pneumonitis. Computed tomographic (CT) findings in 45 patients were correlated with pulmonary function testing and bronchoalveolar lavage. Twenty-seven patients underwent sequential CT examination 0.3-4 years apart, with functional evaluation in 20 of them. In group 1, CT showed diffuse micronodules, ground-glass attenuation, focal air trapping or emphysema, and mild fibrotic changes, with normal lung volumes but impaired diffusing capacity and a predominant lymphocyte alveolitis. In group 2, two categories of chronic forms were identified at CT on the basis of presence or absence of honeycombing. After cessation of exposure, CT showed a return to normal or dramatic improvement in group 1 and considerable reduction in ground-glass attenuation and micronodules in group 2. CT depicted no fibrotic or emphysematous changes during follow-up. Subacute bird breeder hypersensitivity pneumonitis may share CT features with other types of hypersensitivity pneumonitis. CT may help in identification of emphysematous and fibrotic forms of chronic disease.