Merck Manual

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Löffler Syndrome


Joyce Lee

, MD, MAS, University of Colorado School of Medicine

Reviewed/Revised Jun 2021 | Modified Sep 2022
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The diagnosis of Löffler syndrome is based on characteristic and often transient respiratory symptoms, chest x-ray findings, and peripheral blood eosinophilia. It requires the exclusion of other types of eosinophilic lung disease. For example, acute eosinophilic pneumonia Acute Eosinophilic Pneumonia Acute eosinophilic pneumonia (AEP) is a disorder of unknown etiology characterized by rapid eosinophilic infiltration of the lung interstitium. (See also Overview of Eosinophilic Pulmonary Diseases... read more is a distinct entity with acute onset, severe hypoxemia, and typically a lack of increased blood eosinophils at the onset of disease.

The disease usually resolves within 1 month.

Treatment of Löffler syndrome is symptomatic and may consist of corticosteroids.

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NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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