Hypersensitivity pneumonitis producing a BOOP-like reaction: HRCT/pathologic correlation.

The authors report an unusual case of hypersensitivity pneumonitis presenting on high-resolution CT as large and sharply defined nodular opacities caused by extensive bronchiolitis obliterans with organizing pneumonia. Many of the nodules were surrounded by a halo of ground-glass attenuation. To the authors' knowledge, this is the first time these features have been described in association with hypersensitivity pneumonitis.