Hypersensitivity pneumonitis natural history

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Hypersensitivity pneumonitis Microchapters


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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sargun Singh Walia M.B.B.S.[2]


If left untreated, patients with hypersensitivity pneumonitis may progress to develop flu like syndrome, cough, fatigue and malaise.Common complications of hypersensitivity pneumonitis include deterioration of lung function, hypoxemia, pulmonary hypertension and heart failure. Prognosis of hypersensitivity pneumonitis is generally excellent, and total lung recovery occurs in most cases but may take several years.

Natural History, Complications, and Prognosis

Natural History

  • The symptoms of hypersensitivity pneumonitis usually develop in within hours if significant exposure occurs.
  • If the exposure to antigen is removed then the symptoms resolve within hours to days.
  • If left untreated, patients with hypersensitivity pneumonitis may progress to develop flu like syndrome, cough, fatigue and malaise.


  • Common complications of hypersensitivity pneumonitis include:


  • Prognosis of hypersensitivity pneumonitis is generally excellent.
  • Total lung recovery occurs in most cases but may take several years.[3]
  • Surgical lung biopsy can be done to check for fibrosis which is an indicator of poor prognosis.[4]
  • Prediction of prognosis can be done using high resolution CT scan.[5]
  • A study done among old patients suffering from hypersensitivity pneumonitis with no signs of air trapping on CT scan but desaturation with exercise showed poor survival rates.[6]


  1. Conca G (May 1972). "[Prevention of male sterility in childhood]". Minerva Med. (in Italian). 63 (41): 2368–9. PMID 4402194.
  2. Nathan SD (August 2014). "Hypersensitivity pneumonitis and pulmonary hypertension: how the breeze affects the squeeze". Eur. Respir. J. 44 (2): 287–8. doi:10.1183/09031936.00061214. PMID 25082906.
  3. Wang P, Xu ZJ, Xu WB, Shi JH, Tian XL, Feng RE, Zhu YJ (December 2009). "Clinical features and prognosis in 21 patients with extrinsic allergic alveolitis". Chin. Med. Sci. J. 24 (4): 202–7. PMID 20120765.
  4. Sahin H, Brown KK, Curran-Everett D, Hale V, Cool CD, Vourlekis JS, Lynch DA (August 2007). "Chronic hypersensitivity pneumonitis: CT features comparison with pathologic evidence of fibrosis and survival". Radiology. 244 (2): 591–8. doi:10.1148/radiol.2442060640. PMID 17641377.
  5. Hanak V, Golbin JM, Hartman TE, Ryu JH (July 2008). "High-resolution CT findings of parenchymal fibrosis correlate with prognosis in hypersensitivity pneumonitis". Chest. 134 (1): 133–8. doi:10.1378/chest.07-3005. PMID 18403660.
  6. Lima MS, Coletta EN, Ferreira RG, Jasinowodolinski D, Arakaki JS, Rodrigues SC, Rocha NA, Pereira CA (April 2009). "Subacute and chronic hypersensitivity pneumonitis: histopathological patterns and survival". Respir Med. 103 (4): 508–15. doi:10.1016/j.rmed.2008.12.016. PMID 19179061.

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