Chronic hypersensitivity pneumonitis

Chronic hypersensitivity pneumonitis (CHP) refers to hypersensitivity pneumonitis where there is radiological evidence of fibrosis and represents the end-stage of repeated or persistent pneumonitis 7.


HRCT of the chest typically reveals centrilobular, peribronchiolar, indistinct nodular opacities, of various numbers 5. Other features include:

There is often a middle or upper zone predominance of CT findings with sparing of the lung bases, unlike NSIP or UIP which show a lower zone predominance.

The presence of an extensive reticular pattern, traction bronchiectasis, and honeycombing have been shown to be closely related to the presence of histologic fibrosis in chronic HP 6.

The presence of fibrotic changes indicates a poor prognosis.

In some cases it may be difficult to differentiate from that of idiopathic pulmonary fibrosis 4.

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Article Information

rID: 17191
System: Chest
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:
  • Chronic hypersensitivity pneumonitis (CHP)
  • Chronic HP
  • Chronic EAA
  • Chronic extrinsic allergic alveolitis
  • Chronic extrinsic allergic alveolitis (EAA)

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