CTICasesFibrotic Hypersensitivity Pneumonitis
Imaging findings
CT shows basal-predominant interstitial fibrosis but with a conspicuous absence of basilar subpleural traction bronchiectasis and honeycombing, instead showing airway-centric traction bronchiectasis away from the pleural surfaces, reticulation, and areas of lobular air trapping. Surgical lung biopsy demonstrated airway-centric fibrosis, scarred airways with subpleural scarring and bronchiolectasis, peribronchiolar lymphoid accumulation, regions of NSIP-like interstitial fibrosis, and peribronchiolar metaplasia.
Key takeaways
A basal-predominant fibrosing interstitial pneumonia that lacks the peripheral honeycombing and subpleural traction bronchiectasis of UIP and instead shows airway-centric fibrosis and lobular air trapping should raise suspicion for fibrotic hypersensitivity pneumonitis. Pathologic hallmarks include airway-centric (bronchiolocentric) fibrosis, peribronchiolar metaplasia, and bronchiolar metaplasia, though rare fibroblastic foci can occur; absence of granulomas and a known antigen makes the distinction from UIP and CTD-related fibrosis difficult and subject to interobserver variation.
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