Management of Eosinophilia
The management of eosinophilia should be directed at identifying and treating the underlying cause, with helminth infections being the most common identifiable cause in returning travelers and migrants. 1, 2
Diagnostic Approach
Initial Evaluation
Definition: Eosinophilia is defined as a peripheral blood eosinophil count >0.5 × 10⁹/L 1, 2
- Mild: >0.5 × 10⁹/L
- Moderate (hypereosinophilia): >1.5 × 10⁹/L
- Severe: >5.0 × 10⁹/L 2
Essential history elements:
- Travel history to tropical/subtropical areas
- Exposure to freshwater
- Consumption of raw foods
- Walking barefoot
- Current and recent medications
- Allergy history 2
First-line Investigations
- Complete blood count with differential
- Peripheral blood smear
- Comprehensive metabolic panel with liver function tests
- Concentrated stool microscopy (3 samples) for all returning travelers/migrants 1, 2
- Serological tests based on geographical exposure:
- Schistosomiasis serology for Africa/Middle East exposure
- Strongyloides serology for tropical/subtropical exposure
- Filariasis serology for relevant endemic areas 1
Treatment Algorithm
1. Parasitic Infections (Most Common Identifiable Cause)
- Schistosomiasis: Praziquantel 40 mg/kg twice a day for 5 days 2
- Strongyloidiasis: Ivermectin 200 μg/kg/day for 1-2 days 2
- Filariasis: Diethylcarbamazine (specialist consultation recommended) 2
- Hookworm: Albendazole 400 mg daily for 3 days 1, 2
- Cutaneous larva migrans: Ivermectin 200 μg/kg single dose or Albendazole 400 mg/day for 3 days 2
2. Drug-Induced Eosinophilia
- Immediate withdrawal of the suspected causative medication
- Common culprits: NSAIDs, beta-lactam antibiotics, nitrofurantoin, carbamazepine, phenytoin, and sulfasalazine 2
3. Allergic/Atopic Causes
- Antihistamines, corticosteroids, and allergen avoidance 2
4. Idiopathic Hypereosinophilic Syndrome
- First-line: Systemic corticosteroids
- Second-line: Hydroxyurea or interferon-α for refractory cases
- Mepolizumab (anti-IL-5 monoclonal antibody) as a steroid-sparing agent 2, 3
5. Clonal/Neoplastic Eosinophilia
- Tyrosine kinase inhibitors (e.g., imatinib) for myeloid disorders with specific genetic abnormalities (e.g., FIP1L1-PDGFRA fusion) 3, 4
Important Considerations
Geographical Approach
- The UK guidelines recommend a geographical approach to investigating asymptomatic eosinophilia in returning travelers and migrants 1
- This approach helps target specific parasitic infections based on travel history
Monitoring and Follow-up
- Regular monitoring of blood counts is crucial for patients on treatment
- For mild, transient eosinophilia: Follow-up CBC to confirm resolution
- For persistent unexplained eosinophilia: Regular monitoring for end-organ damage 2
Complications of Untreated Eosinophilia
- Persistent eosinophilia (>1.5 × 10⁹/L for >3 months) can cause significant organ damage:
Pitfalls to Avoid
- Cross-reactivity in serological tests: False positives can occur when testing for parasites not endemic to the region visited 1
- Delayed treatment: Can lead to irreversible organ damage, particularly cardiac complications 2, 3
- Multiple causes: Up to 28% of patients may have multiple causes of eosinophilia 1
- Overlooking drug causes: Always consider medication-induced eosinophilia, which typically develops 2-6 weeks after starting treatment 2
Special Situations
- For drug procurement difficulties (unlicensed or hard-to-source medications), contact specialized tropical medicine centers 1
- For immunocompromised patients with Strongyloides, urgent treatment is essential to prevent potentially fatal hyperinfection syndrome 1, 2
By following this structured approach to diagnosing and treating eosinophilia, clinicians can effectively manage this condition while minimizing the risk of complications from persistent eosinophilia.