Eosinophilic Pneumonia

In a patient with new pulmonary opacities and respiratory symptoms, obtain room-air oxygenation and assess for an AEP phenotype: febrile respiratory illness lasting no more than 1 month, bilateral infiltrates, and severe hypoxemia defined by PaO2 <60 mm Hg, PaO2/FiO2 ≤300 mm Hg, or room-air oxygen saturation <90%. This presentation can progress to ARDS and may be mistaken for severe community-acquired pneumonia. ATS Journals+1ATS JournalsAcute Eosinophilic Pneumonia. Causes, Diagnosis, and ManagementPubMedAcute Eosinophilic Pneumonia - PMC

Confirm lung eosinophilia with bronchoscopy and BAL when clinically feasible. A BAL eosinophil differential >25% is diagnostic in a compatible setting; a proportion >40% is found mainly in CEP. BAL eosinophils between 3% and 40% are less specific and occur in other interstitial lung diseases, so interpret subthreshold results with the imaging pattern, peripheral eosinophil count, exposure history, and microbiology. PubMed+1PubMedEosinophilic Pneumonia - PMCPubMedBronchoalveolar lavage as a diagnostic procedure: a review of known cellular and molecular findings in various lung diseases

Do not exclude AEP because the admission complete blood count lacks eosinophilia. Peripheral eosinophilia may be absent or mild early in AEP and may also be suppressed by antecedent corticosteroids. When using blood eosinophilia as the principal evidence of pulmonary eosinophilic disease, an absolute eosinophil count >1 × 10^9/L with typical clinical-radiologic features is more persuasive; counts >1.5 × 10^9/L further support the diagnosis. PubMed+2PubMedEosinophilic Pneumonia - PMCPubMedPulmonary Eosinophilia - StatPearls - NCBI Bookshelf - NIHPubMedBronchoalveolar lavage as a diagnostic procedure: a review of known cellular and molecular findings in various lung diseases

Classify as probable AEP when illness is acute, febrile, and hypoxemic with diffuse bilateral radiographic opacities and BAL eosinophils >25%, after excluding infection and another defined eosinophilic lung disease. Modified criteria define definite AEP by respiratory illness of 1 month or less, pulmonary infiltrates on radiography or CT, pulmonary eosinophilia, and no alternative specific eosinophilic disorder. ATS Journals+1ATS JournalsAcute Eosinophilic Pneumonia. Causes, Diagnosis, and ManagementPubMedAcute Eosinophilic Pneumonia - PMC

Classify as CEP when respiratory symptoms have persisted for 2 to 4 weeks with marked tissue and peripheral blood eosinophilia and alveolar consolidation with air bronchograms and/or ground-glass opacities. The combination of peripheral consolidation, blood eosinophilia, BAL eosinophilia, and corticosteroid response is often sufficient without biopsy. PubMed+1PubMedAcute and chronic eosinophilic pneumonia: an overview - PMCPubMedAcute and chronic eosinophilic pneumonia: an overview

When imaging suggests CEP but organizing pneumonia remains plausible, favor CEP when eosinophilia is prominent in blood or BAL. Compared with CEP, organizing pneumonia more often has peribronchovascular consolidation and a reverse-halo sign; mild BAL eosinophilia can occur in cryptogenic organizing pneumonia and should not alone establish CEP. PubMed+1PubMedEosinophilic Pneumonia - PMCPubMedAcute and chronic eosinophilic pneumonia: an overview

Take a medication and substance history that captures recently started prescription agents, over-the-counter products, illicit drugs, tobacco changes, vaping, cannabis exposure, and other inhalational exposures. Drugs recognized in reports of eosinophilic pneumonia include daptomycin, minocycline, venlafaxine, ranitidine, paracetamol, and allopurinol; discontinue a plausible culprit rather than continuing exposure while treating a presumed idiopathic syndrome. Nature+2NatureExploratory disproportionality analysis of potentially drug-induced eosinophilic pneumonia using United States Food and Drug Administration adverse event reporting system | Scientific ReportsWolters KluwerDrug-induced eosinophilic pneumonia: A review of 196 case... : MedicinePubMedAcute Eosinophilic Pneumonia - PMC

Select infection testing from exposure history before corticosteroid treatment when possible. For relevant fungal exposure, evaluate for Aspergillus and Coccidioides with culture, microscopy, or serologic studies; for relevant parasite exposure, evaluate especially for Strongyloides. Aspergillus infection can clinically mimic AEP but requires antifungal treatment rather than treatment directed solely at eosinophilic inflammation. PubMedPubMedAcute Eosinophilic Pneumonia - PMC

Screen for systemic eosinophilic disorders when pulmonary disease coexists with asthma, chronic sinonasal disease, neuropathy, extrapulmonary organ involvement, or marked persistent eosinophilia. EGPA can produce peripheral or random ground-glass opacities and consolidations; ANCA is positive in approximately 40% of cases, predominantly p-ANCA with myeloperoxidase activity, so a negative ANCA does not exclude EGPA. PubMedPubMedPulmonary Eosinophilia - StatPearls - NCBI Bookshelf - NIH

For suspected AEP with severe hypoxemia, provide oxygen and escalate ventilatory support as required while completing bronchoscopy and infectious evaluation. AEP can present as ARDS, and reported diagnostic frameworks include prompt corticosteroid response as a characteristic feature; however, infection and alternative eosinophilic syndromes must be excluded rather than inferred from steroid responsiveness alone. ATS Journals+1ATS JournalsAcute Eosinophilic Pneumonia. Causes, Diagnosis, and ManagementPubMedAcute Eosinophilic Pneumonia - PMC

For CEP, corticosteroid therapy commonly produces a rapid clinical response, but relapse after tapering is a defining management problem. Monitor symptoms, oxygenation, chest imaging, and peripheral eosinophil counts during dose reduction; recurrent disease may require long-term maintenance corticosteroid therapy. BMJ+1BMJOptimal dose of maintenance steroid therapy for relapse ...PubMedAcute and chronic eosinophilic pneumonia: an overview

For drug-associated disease, withdrawal of the suspected medication is the essential cause-directed action. For infection-associated disease, redirect therapy to the identified pathogen; do not use clinical eosinophilia or a transient corticosteroid response to substitute for fungal or helminthic testing in an exposed patient. Nature+1NatureExploratory disproportionality analysis of potentially drug-induced eosinophilic pneumonia using United States Food and Drug Administration adverse event reporting system | Scientific ReportsPubMedAcute Eosinophilic Pneumonia - PMC

A compatible syndrome with BAL eosinophilia >25% generally obviates video-assisted thoracoscopic surgical lung biopsy. Reserve biopsy for inconsistency among clinical course, laboratory data, and imaging; tissue can confirm eosinophilic pneumonia and may distinguish competing processes such as vasculitis, organizing pneumonia, malignancy, or another interstitial lung disease. PubMed+2PubMedEosinophilic Pneumonia - PMCATS JournalsAcute Eosinophilic Pneumonia. Causes, Diagnosis, and ManagementPubMedPulmonary Eosinophilia - StatPearls - NCBI Bookshelf - NIH

If BAL eosinophils are below 25% but suspicion remains high, do not treat the threshold as an absolute exclusion. BAL can be affected by prior corticosteroid exposure, and lung biopsy is a reasonable alternative when a definitive diagnosis will alter therapy or when imaging is atypical. PubMed+1PubMedCT-Guided Percutaneous Lung Biopsy in the Diagnosis of Asthma-Associated Chronic Eosinophilic Pneumonia: A Case Report - PubMedPubMedEosinophilic Pneumonia - PMC

Escalate evaluation beyond a lung-limited diagnosis when pulmonary eosinophilia accompanies neuropathy, sinonasal disease, asthma, marked blood eosinophilia, or other organ involvement. In these settings, pathology and directed immunologic or molecular testing may identify EGPA, hypereosinophilic syndrome, malignancy, or another systemic cause. ScienceDirect+1ScienceDirectDifferential Diagnosis of Eosinophilic Lung DiseasesPubMedPulmonary Eosinophilia - StatPearls - NCBI Bookshelf - NIH