CTICasesFibrotic Hypersensitivity Pneumonitis (Indeterminate for UIP Pattern)
Imaging findings
CT in a patient with a known fibrosing interstitial lung disorder shows a fibrotic pattern with reticulation and traction bronchiectasis, particularly extensive in the left upper lobe, with additional disease in the lower lung zones but overall basal predominance and substantial apical lung involvement; bands of fibrosis track from the periphery along the bronchovascular bundles across much of the lung, a perilobular pattern, with heterogeneity suggesting air trapping on some images.
Key takeaways
The extensive apical involvement makes this pattern indeterminate for, or not suggestive of, usual interstitial pneumonia under current fibrotic-lung-disease classification schemes, and the perilobular fibrosis bands tracking along bronchovascular bundles are considered a finding suggestive of hypersensitivity pneumonitis, also seen in organizing pneumonia; pathology from a multi-lobe biopsy showed only scattered fibroblastic foci without well-formed granulomas, an ambiguous, non-diagnostic picture illustrating that even tissue sampling can fail to definitively separate fibrotic hypersensitivity pneumonitis from UIP when classic granulomas are not identified.
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