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:
- ground-glass opacities
- lobular areas of hyperlucency (mosaic perfusion) caused by bronchiole obstruction
- areas of pulmonary fibrosis and honeycombing
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.
Treatment and prognosis
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.
- 1. Hirschmann JV, Pipavath SN, Godwin JD. Hypersensitivity pneumonitis: a historical, clinical, and radiologic review. Radiographics. 2009;29 (7): 1921-38. doi:10.1148/rg.297095707 - Pubmed citation
- 2. Adler BD, Padley SP, Müller NL et-al. Chronic hypersensitivity pneumonitis: high-resolution CT and radiographic features in 16 patients. Radiology. 1992;185 (1): 91-5. Radiology (abstract) - Pubmed citation
- 3. Silva CI, Müller NL, Lynch DA et-al. Chronic hypersensitivity pneumonitis: differentiation from idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia by using thin-section CT. Radiology. 2008;246 (1): 288-97. doi:10.1148/radiol.2453061881 - Pubmed citation
- 4. Lynch DA, Newell JD, Logan PM et-al. Can CT distinguish hypersensitivity pneumonitis from idiopathic pulmonary fibrosis? AJR Am J Roentgenol. 1995;165 (4): 807-11. AJR Am J Roentgenol (abstract) - Pubmed citation
- 5. Buschman DL, Gamsu G, Waldron JA et-al. Chronic hypersensitivity pneumonitis: use of CT in diagnosis. AJR Am J Roentgenol. 1992;159 (5): 957-60. AJR Am J Roentgenol (abstract) - Pubmed citation
- 6. Sahin H, Brown KK, Curran-everett D et-al. Chronic hypersensitivity pneumonitis: CT features comparison with pathologic evidence of fibrosis and survival. Radiology. 2007;244 (2): 591-8. doi:10.1148/radiol.2442060640 - Pubmed citation
- 7. From the European respiratory monograph http://erm.ersjournals.com/content/ermpl/1/SEC12.body