Acute Eosinophilic Pneumonia

Definition

Acute respiratory insufficiency associated with pulmonary eosinophil infiltration

Acute onset of dyspnea, cough and fever
- Rapid progression to respiratory insufficiency
- Generally under 1-2 weeks
- Presentation similar to diffuse alveolar damage / acute interstitial pneumonia
Mean age 30, usually previously healthy
Rapid response to steroids
- Does not relapse

Blood eosinophils usually normal
- Occasionally elevated but generally <500/mm3
Demonstration of pulmonary eosinophilia required for diagnosis with either:
- Bronchoalveolar lavage (BAL) fluid shows eosinophils > lymphocytes
  - Usually >25%
  - Other cells are macrophages and neutrophils
- Tissue biopsy shows prominent eosinophilic infiltrate
  - Biopsy is not usually necessary for diagnosis but may help rule out infection
  - Intra-alveolar and usually interstitial
  - 5-25% eosinophils is consistent with diagnosis, >25% is suggestive
    - Eosinophils are rare in normal lung (<2%)
  - Changes of diffuse alveolar damage with hyaline membranes usually present
  - Changes of cryptogenic organizing pneumonia (BOOP) frequently present
Known causes must be ruled out
- Drugs including antibiotics, non-steroidal anti-inflammatory, anti-hypertensive, heroin, cocaine
- Organisms including fungi and parasites

Gerald J Berry MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates: 11/20/10