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e nonfibrotic typical HP pattern is characterized by (A) centrilobular nodules, (B)
mosaic attenuation on an inspiratory scan, and (C) air trapping on an expiratory scan.
(D) e nonfibrotic compatible-with-HP pattern is exemplified by uniform and subtle
ground-glass opacity and cysts. e fibrotic typical HP pattern consists of (E) coarse
reticulation and minimal honeycombing in a random axial distribution with no zonal
predominance in association with (F) small airway disease.
e fibrotic compatible-with-HP pattern varies in the patterns and/or distribution
of lung fibrosis (e.g., basal and subpleural predominance, [G] upper-lung-zone
predominance, [H] central [or peribronchovascular] predominance [arrows], or [I]
fibrotic ground-glass attenuation seen alone or in association with small airway disease).
e fibrotic indeterminate-for-HP pattern includes the usual interstitial pneumonia
pattern, nonspecific interstitial pneumonia pattern, organizing pneumonia–like pattern,
or truly indeterminate findings.
Figure 1. "Typical hypersensitivity pneumonitis (HP)" and
"compatible-with-HP" high-resolution computed
tomography patterns.
