Acute eosinophilic pneumonia

Last revised by Henry Knipe on 27 Sep 2022

Acute eosinophilic pneumonia is a type of eosinophilic lung disease diagnosed when the following combination of clinical and radiographic findings occur 5,7:

  • febrile illness of less than five days' duration
  • hypoxemia
  • diffuse alveolar or mixed alveolar-interstitial opacities on chest radiography
  • bronchoalveolar lavage (BAL) fluid consisting of >25% eosinophils
  • absence of parasitic, fungal, or other infection
  • prompt and complete response to corticosteroids
  • no relapse after discontinuation of corticosteroids


Most cases are idiopathic, however, a link to new or binge smoking in a subset of patients has been suggested 8. Peripheral blood eosinophil counts are usually normal, although they can become elevated during the subsequent clinical course. A very high eosinophil count in bronchoalveolar lavage is characteristic of the condition.

Radiographic features

Imaging features should be interpreted in the correct clinical context.


Described features include 4,6,9:

Zonal distribution:

  • central-to-peripheral zonal distribution 6
    • random ~60%
    • peripheral ~30%
    • central ~10%
  • apicobasal overall zonal distribution 6
    • random ~65% 
    • lower lobes ~30% 
    • upper lobes ~15% 

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Cases and figures

  • Case 1
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  • Case 2
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