Acute Eosinophilic Pneumonia

Acute eosinophilic pneumonia (AEP) is a rapidly progressive febrile illness with hypoxaemic respiratory failure and pulmonary eosinophilia, typically in young adults.

Associated with recent onset of cigarette smoking or increased smoking (within 1 month in majority), inhalation of dust or smoke, vaping, cocaine and other drugs; also daptomycin, minocycline, sertraline, and rarely infection.

Mean age 20 to 40, male predominance. No recurrence after resolution.

Distinguished from chronic eosinophilic pneumonia by acute onset (under 1 month), lack of peripheral eosinophilia at presentation, and complete recovery.

• Acute onset over days (1 to 5 days): fever, dry cough, pleuritic chest pain, dyspnoea, myalgia, malaise.
• Hypoxaemia that can progress to acute respiratory failure and ARDS requiring ventilation within 48 hours.
• Bibasal crackles; no wheeze; no extrapulmonary disease.

Allen criteria (essential)

• Acute febrile illness under 5 days.
• Bilateral diffuse pulmonary infiltrates.
• Hypoxaemia (PaO2 under 60 mmHg or SpO2 under 90% on room air).
• Pulmonary eosinophilia: BAL eosinophils over 25% (usually 25 to 50%) or eosinophilic pneumonia on biopsy.
• Absence of infection or other known cause of eosinophilia.

Other tests

• Peripheral eosinophilia typically absent at onset but may rise over days.
• Chest imaging: bilateral ground glass opacities, interlobular septal thickening, small pleural effusions (Kerley lines).
• Rule out infection (cultures, viral panel), heart failure, drug causes.
• Bronchoscopy with BAL is the key diagnostic test.

• Supportive care with oxygen, high flow or non invasive ventilation; mechanical ventilation (lung protective, tidal volume 6 mL/kg) if needed.
• Methylprednisolone 60 to 125 mg IV every 6 hours (1 mg/kg every 6 hours) until improvement (24 to 72 hours), then prednisolone 40 to 60 mg daily tapered over 2 to 4 weeks.
• Rapid response to corticosteroids is characteristic, with resolution in 3 to 7 days; relapse is uncommon.
• Stop the precipitant (smoking cessation, discontinue implicated drug).
• Empirical antibiotics until infection is excluded, discontinued once cultures are negative.
• Follow up chest imaging and lung function; recovery is complete without fibrosis.