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Acute Eosinophilic Pneumonia

By

Joyce Lee

, MD, MAS, University of Colorado School of Medicine

Last full review/revision Jun 2021| Content last modified Jun 2021
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Acute eosinophilic pneumonia (AEP) is a disorder of unknown etiology characterized by rapid eosinophilic infiltration of the lung interstitium.

In contrast to chronic eosinophilic pneumonia Chronic Eosinophilic Pneumonia Chronic eosinophilic pneumonia (CEP) is a disorder of unknown etiology characterized by an abnormal, chronic accumulation of eosinophils in the lung. (See also Overview of Eosinophilic Pulmonary... read more , acute eosinophilic pneumonia is an acute illness that does not usually recur. Incidence and prevalence are unknown. Acute eosinophilic pneumonia can occur at any age but most often affects patients between 20 and 40 years, with a male-to-female ratio of 2:1.

The cause is unknown, but acute eosinophilic pneumonia may be an acute hypersensitivity reaction Drug Hypersensitivity Drug hypersensitivity is an immune-mediated reaction to a drug. Symptoms range from mild to severe and include rash, anaphylaxis, and serum sickness. Diagnosis is clinical; skin testing is occasionally... read more to an unidentified inhaled antigen in an otherwise healthy person. Cigarette or other smoke exposure may be involved.

Symptoms and Signs of Acute Eosinophilic Pneumonia

Acute eosinophilic pneumonia causes an acute febrile illness of short duration (usually < 7 days). Symptoms are nonproductive cough, dyspnea, malaise, myalgias, night sweats, and pleuritic chest pain.

Signs include tachypnea, fever (often > 38.5° C), and bibasilar inspiratory crackles and, occasionally, rhonchi on forced exhalation.

Diagnosis of Acute Eosinophilic Pneumonia

  • High-resolution CT (HRCT)

  • Usually complete blood count (CBC), pleural fluid analysis, and pulmonary function testing

  • Bronchoscopy for lavage and, sometimes, biopsy

The diagnosis of acute eosinophilic pneumonia is suspected in patients with symptoms of acute pneumonia that progress to respiratory failure and do not respond to antibiotics. Diagnosis is based on findings from routine testing and is confirmed by bronchoscopy.

The chest x-ray initially may show only subtle reticular or ground-glass opacities, often with Kerley B lines. Isolated alveolar (about 25% of cases) or reticular (about 25% of cases) opacities may also be observed. Unlike in chronic eosinophilic pneumonia, in acute eosinophilic pneumonia opacities are not characteristically localized to the lung periphery. Small pleural effusions Pleural Effusion Pleural effusions are accumulations of fluid within the pleural space. They have multiple causes and usually are classified as transudates or exudates. Detection is by physical examination and... read more Pleural Effusion occur in two thirds of patients and are frequently bilateral.

HRCT is always abnormal with bilateral, random, patchy ground-glass or reticular opacities.

Pleural fluid examination shows marked eosinophilia and high pH.

Bronchoscopy Bronchoscopy Bronchoscopy is the introduction of an endoscope into the airways. Flexible fiberoptic bronchoscopy is used for virtually all diagnostic, and most therapeutic, indications. Flexible bronchoscopes... read more Bronchoscopy should be done for lavage and, occasionally, biopsy. Bronchoalveolar lavage fluid often shows a high number and percentage (> 25%) of eosinophils. The most common histopathologic features on biopsy include eosinophilic infiltration with acute and organizing diffuse alveolar damage, but few patients have undergone lung biopsy.

Treatment of Acute Eosinophilic Pneumonia

  • Systemic corticosteroids

Some patients with acute eosinophilic pneumonia improve spontaneously. Most are treated with prednisone 40 to 60 mg orally once a day. In patients with respiratory failure, methylprednisolone 60 to 125 mg IV every 6 hours is preferred.

The prognosis of acute eosinophilic pneumonia is usually good; response to corticosteroids and complete recovery are common. Pleural effusions resolve more slowly than parenchymal opacities.

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