From the Guidelines
Pleural fluid eosinophilia is most commonly caused by air or blood in the pleural space, medication reactions, parasitic infections, fungal diseases, and malignancies, and a thorough diagnostic workup including detailed medication history, chest imaging, and microbiological studies is essential to determine the underlying cause. The presence of eosinophils in pleural fluid often represents an inflammatory response to foreign substances or antigens in the pleural space, which explains why conditions introducing air, blood, or foreign materials into this space commonly trigger this finding 1.
Common Causes of Pleural Fluid Eosinophilia
- Air or blood in the pleural space (pneumothorax or hemothorax)
- Medication reactions
- Parasitic infections
- Fungal diseases
- Malignancies
When pleural fluid eosinophilia is identified, management depends on treating the underlying cause. For medication-induced cases, discontinuation of the offending drug is recommended. Parasitic infections require appropriate antiparasitic therapy, such as albendazole 400mg twice daily for 5-7 days for many helminthic infections or praziquantel for schistosomiasis, as suggested by studies on returning travelers and migrants from the tropics 1. Fungal infections may require antifungal agents like fluconazole or amphotericin B depending on the pathogen. Malignancy-related eosinophilic effusions typically require oncologic consultation and treatment of the underlying cancer.
Diagnostic Approach
A thorough diagnostic workup should include:
- Detailed medication history
- Chest imaging
- Appropriate microbiological studies
- Consideration of the patient's travel history and potential exposure to parasitic or fungal infections, as highlighted in the study on eosinophilia in returning travelers and migrants from the tropics 1.
It is also important to note that asbestos exposure can cause pleural effusions with eosinophilia, as discussed in the study on diagnosis and initial management of nonmalignant diseases related to asbestos 1. However, this is less common and typically occurs in the context of other asbestos-related diseases.
Overall, the key to managing pleural fluid eosinophilia is to identify and treat the underlying cause, and a thorough diagnostic workup is essential to achieve this goal.
From the Research
Causes of Pleural Fluid Eosinophilia
The causes of pleural fluid eosinophilia, also known as eosinophilic pleural effusion (EPE), can be varied and include:
- Idiopathic cases, which account for 14%-25% of EPE cases, even after thorough work-up 2
- Malignant diseases, such as angioimmunoblastic T cell lymphoma 3 and malignant histiocytic lymphoma 4
- Pulmonary infections, including pneumococcal empyema 4
- Collagen vascular diseases 4
- Tuberculosis 4
- Parasitic infections, such as hookworm 3
- Sarcoidosis, which can present with an unusual combination of clinical and laboratory findings, including eosinophilic pleural effusion, peripheral eosinophilia, pleural thickening, and hepatosplenomegaly 5
- Eosinophilic lung diseases, such as eosinophilic pneumonia and Löffler syndrome, which can be caused by parasitic infections, drugs, toxins, and fungi 6
Common Characteristics
Eosinophilic pleural effusion is typically defined as having eosinophils exceeding 10% of the pleural fluid WBC differential 2, 4. It is usually exudative and can account for 1% to 8% of all pleural effusions 4. Spontaneous resolution and a favorable prognosis are common in this entity, but prudent clinical follow-up is advised 4.