Table 1.

Similarities and differences in clinical, radiological and histopathological features between fibrotic HP and idiopathic pulmonary fibrosis (IPF).

Features	Fibrotic HP	IPF
Demographics
Sex	No difference	More frequent in men
Smoking	Protective	Risk factor
Age	No predilection	More frequent > 55 years
Clinical symptoms/history
Clubbing	Often	Often
Squeaks	Typical	Absent
Bibasal crackles	Frequent	Frequent
Systemic disease features (fever, joint pains, fatigue)	Often	Absent
Exposure to antigens	Frequent	Rare
Positive precipitins	Frequent	Rare
Imaging (CT)
Distribution	Upper lobe predominance	Peripheral, predominantly basal
Mosaic attenuation	Frequent	Absent/Limited
Nodules	Frequent	Absent
Interlobular septal thickening	Often	Absent/Limited
Honeycombing	Often	Frequent (typical for UIP pattern)
Bronchocentricity	Frequent	Absent
Discrete cysts	Often	Absent
Consolidation	Rare	Absent
Bronchoalveolar lavage (BAL)	Lymphocytosis > 25–30%	Lymphocytosis < 20%
Histological
Fibroblast foci	Often	Frequent
Granulomas/giant cells/Schaumann bodies	Frequent	Rare
Organizing pneumonia	Rare	Rare
Honeycombing	Often	Frequent
Paraseptal subpleural distribution	Often	Frequent
Bronchocentricity	Frequent	Absent