Chronic Eosinophilic Pneumonia

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Chronic Eosinophilic Pneumonia

Neumonía eosinofílica crónica

만성 호산구성 폐렴

Keywords: chronic eosinophilic pneumonia, peripheral airspace opacities, photographic negative, eosinophilia, prednisone, CT scan, allergic asthma, corticosteroid response

Introduction

Chronic eosinophilic pneumonia (CEP) is a rare but distinct form of idiopathic interstitial lung disease characterized by prominent pulmonary and peripheral eosinophilic infiltration. 

Often affecting middle-aged women with a history of asthma or atopy, it presents insidiously with systemic symptoms that mimic more common pulmonary infections or malignancies. 

A hallmark radiological feature, described as the “imaging negative of pulmonary edema,” provides a vital diagnostic clue and has been consistently associated with CEP.

 This case-based discussion outlines the pathogenesis, clinical and imaging characteristics, diagnosis, and treatment of CEP.

Case Summary

A 54-year-old woman with known allergic rhinitis and asthma presented with a 3-month history of worsening cough and dyspnea, accompanied by fever, chills, night sweats, and unintended 9-kg weight loss. 

Chest auscultation revealed wheezing and expiratory rhonchi. Laboratory tests indicated marked eosinophilia.

High-resolution computed tomography (HRCT) of the chest demonstrated upper lobe–predominant peripheral and subpleural consolidations, sparing the perihilar regions—a pattern reminiscent of a “imaging negative of pulmonary edema.” 

Bronchoalveolar lavage (BAL) revealed a 74% eosinophil count. 

Tests for Aspergillus fumigatus IgE, coccidioidomycosis antibodies, and antineutrophil cytoplasmic antibodies (ANCA) were negative. 

The diagnosis was confirmed as chronic eosinophilic pneumonia, and oral prednisone therapy led to rapid symptomatic and radiographic improvement.

Discussion

Cause and Etiology

Chronic eosinophilic pneumonia is idiopathic in most cases, although associations with asthma, allergic disorders, and environmental exposures are well established. Unlike acute eosinophilic pneumonia, which often presents in previously healthy individuals, CEP typically occurs in patients with an allergic diathesis.

Etiological hypotheses include:

  • Allergic pathogenesis involves a type I hypersensitivity mechanism.

  • Th2-dominant immune response: leading to increased IL-5-mediated eosinophilic recruitment.

  • Chronic antigen exposure, such as molds, medications, or environmental pollutants.

Pathophysiology

The underlying mechanism centers around the infiltration of eosinophils into the pulmonary interstitium and alveolar spaces. 

Eosinophils release cytotoxic proteins such as major basic protein and eosinophil peroxidase, leading to alveolar inflammation and consolidation. 

Chronic inflammation contributes to tissue remodeling, respiratory symptoms, and abnormal gas exchange.

Epidemiology

CEP constitutes about 2.5% of interstitial lung diseases and is more common in:

  • Middle-aged women (typically in their 40s to 50s)

  • Patients with a history of asthma or atopy

  • Nonsmokers

The incidence remains underreported due to frequent misdiagnosis as pneumonia or cryptogenic organizing pneumonia.

Clinical Presentation

Patients often present subacutely with nonspecific respiratory and constitutional symptoms:

  • Persistent cough and progressive dyspnea

  • Wheezing, particularly in asthmatic individuals

  • Fever, chills, night sweats

  • Weight loss and malaise

On examination, wheezes and rhonchi are common, mimicking bronchial asthma or pneumonia.

Imaging Features

Radiographic imaging is crucial in diagnosing CEP. The characteristic finding is the “imaging negative of pulmonary edema.”

Figure 1. Initial chest X-ray showing bilateral peripheral airspace opacities consistent with CEP.

Figure 2. High-resolution CT scan shows upper lobe–dominant peripheral and subpleural consolidation with central sparing.

Figure 3. Follow-up chest radiograph after 17 days of corticosteroid therapy demonstrates near-complete resolution of opacities.

Other CT findings include:

  • Ground-glass opacities

  • Interlobular septal thickening

  • Consolidations that migrate over time (transient)

Diagnosis

The diagnosis of CEP is based on clinical history, peripheral eosinophilia, imaging findings, and the exclusion of infectious, malignant, and vasculitic causes.

Key Diagnostic Criteria:

  • Peripheral blood eosinophilia (>500 cells/μL)

  • BAL eosinophilia (>25%)

  • Negative infectious workup

  • Response to corticosteroids

  • Typical imaging (photographic negative sign)

Treatment

Mainstay Therapy: Oral corticosteroids (e.g., prednisone 0.5–1 mg/kg/day)

  • Rapid clinical improvement is often within days

  • Radiologic resolution within 2–3 weeks

Duration: Typically tapered over 6–12 months
Relapse Risk: Up to 50% if taper is too rapid
Steroid-Sparing Agents: Considered in relapsing cases (e.g., methotrexate)

Prognosis

CEP generally has an excellent prognosis when treated promptly with corticosteroids. However, chronicity and relapses can occur in up to 50% of cases.

Predictors of favorable outcome:

  • Early diagnosis

  • Prompt corticosteroid initiation

  • Asthma control

Complications (if untreated):

  • Progressive fibrosis

  • Hypoxemia

  • Secondary infections due to prolonged steroid use

Quiz

1. What is the most likely diagnosis based on the clinical and radiologic findings?

A. Allergic bronchopulmonary aspergillosis
B. Chronic eosinophilic pneumonia
C. Cryptogenic organizing pneumonia
D. Drug-induced eosinophilic pneumonia
E. Pulmonary tuberculosis

2. Which imaging pattern is pathognomonic for chronic eosinophilic pneumonia?

A. Honeycombing
B. Centrilobular nodules
C. Photographic negative of pulmonary edema
D. Tree-in-bud
E. Miliary pattern

3. What is the most definitive diagnostic test for confirming CEP?

A. Sputum culture
B. Bronchoalveolar lavage with eosinophil count
C. Skin prick test
D. D-dimer test
E. Thoracentesis

Answer & Explanation

1. Answer: B. Chronic eosinophilic pneumonia. Explanation: The peripheral airspace opacities, eosinophilia, and response to prednisone are classic for CEP.

2. Answer: C. Photographic negative of pulmonary edema. Explanation: This radiographic pattern of peripheral opacities with central sparing is the hallmark of CEP.

3. Answer: B. Bronchoalveolar lavage with eosinophil count. Explanation: BAL eosinophilia (>25%) supports the diagnosis when combined with imaging and clinical history.

Conclusion

Chronic eosinophilic pneumonia is a rare yet highly treatable interstitial lung disease that requires a high index of suspicion, especially in middle-aged women with asthma presenting with constitutional symptoms and characteristic imaging. The “photographic negative of pulmonary edema” is a distinctive radiologic clue that can expedite diagnosis. Corticosteroid therapy leads to rapid symptom resolution and radiologic recovery in most patients, though relapses may necessitate prolonged treatment or additional immunosuppressive agents.

References

  1. J. J. Carrington et al., "The radiologic manifestations of eosinophilic lung disease," Radiology, vol. 112, no. 1, pp. 1–14, 1974.

  2. R. Marchand and C. Reynaud-Gaubert, "Chronic eosinophilic pneumonia," Orphanet J. Rare Dis., vol. 1, no. 1, pp. 1–5, 2006.

  3. A. Cottin, “Eosinophilic lung diseases,” Clin. Chest Med.., vol. 35, no. 3, pp. 535–556, 2014.

  4. M. Allen, "Radiologic patterns of eosinophilic lung diseases," Chest, vol. 110, no. 2, pp. 540–546, 1996.

  5. M. Mochimaru et al., "Chronic eosinophilic pneumonia: Imaging findings in six cases," Respiration, vol. 73, no. 5, pp. 758–762, 2006.

  6. D. C. Lynch, “Imaging of idiopathic interstitial pneumonias,” Radiol. Clin. N. Am., vol. 37, no. 1, pp. 135–158, 1999.

  7. Y. Suzuki et al., "Role of BAL in diagnosis of eosinophilic pneumonia," Eur. Respir. J., vol. 14, no. 3, pp. 681–687, 1999.

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