(See also Overview of Interstitial Lung Disease.)
Parasitic infections, especially ascariasis, may be the cause, but an identifiable etiologic agent is not found in up to one third of patients.
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 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.