Treatment of Elevated Eosinophils
The treatment of elevated eosinophils (9.9 × 10⁹/L) should focus first on identifying and treating the underlying cause, followed by specific therapies to reduce eosinophil counts and prevent end-organ damage. 1
Diagnostic Approach
Initial Evaluation
- Complete blood count with differential to confirm eosinophilia
- Comprehensive metabolic panel with liver function tests
- Peripheral blood smear review
- Serum tryptase and vitamin B12 levels (to evaluate for myeloproliferative variants)
History and Risk Assessment
- Travel history: Especially to areas endemic for helminth infections
- Medication history: Focus on NSAIDs, beta-lactam antibiotics, and other common culprits
- Allergy/atopy history: Asthma, eczema, hay fever
- Symptoms of organ involvement: Cardiac, pulmonary, gastrointestinal, and skin
Additional Testing Based on Clinical Suspicion
- For travelers/migrants: Parasite serology and stool examination for ova and parasites
- For persistent unexplained eosinophilia: Bone marrow aspirate and biopsy with cytogenetic studies
Treatment Algorithm
1. Parasitic Infections
- For returning travelers with suspected parasitic infection:
- Empiric treatment with albendazole 400 mg twice daily for 3 days 2
- For Strongyloides: Ivermectin 200 μg/kg daily for 2 days
- For Schistosomiasis (Katayama syndrome): Praziquantel 40 mg/kg as a single dose, repeated at 6-8 weeks 2
- For liver flukes: Praziquantel 25 mg/kg three times daily for 2-3 consecutive days 2
2. Eosinophilic Esophagitis (if GI symptoms present)
- First-line: Proton pump inhibitor therapy twice daily for 8-12 weeks 2
- Second-line: Topical steroids 2
- For refractory cases: Consider dietary therapy
- Elimination diets under supervision of a dietitian
- Amino acid-based formula (elemental diet) for severe cases 2
3. Hypereosinophilic Syndrome (HES)
- First-line: Corticosteroids (prednisone 1 mg/kg/day) 1, 3
- Steroid-sparing agents:
- Hydroxyurea
- Interferon-α
- Mepolizumab (IL-5 antagonist) for idiopathic HES 3
4. Myeloid/Lymphoid Neoplasms with Eosinophilia
- For PDGFRA or PDGFRB rearrangements: Imatinib 3
- For other variants: Targeted therapy based on molecular findings
Monitoring and Follow-up
- Mild, transient eosinophilia: Follow-up CBC to confirm resolution
- Patients on treatment: Regular monitoring of blood counts and eosinophilia
- Persistent unexplained eosinophilia: Regular monitoring for end-organ damage
- If eosinophilia persists at ≥1.5 × 10⁹/L for >3 months: Referral to hematologist 1
Important Considerations
- End-organ damage assessment is critical as it determines treatment urgency
- Corticosteroid treatment for neurological involvement requires exclusion of strongyloidiasis to prevent hyperinfection 2
- Combination therapy (drugs and diet) should be reserved for selected patients who fail monotherapy 2
- Novel biologics (dupilumab, benralizumab) show promise for refractory cases but require further study 2, 3
Common Pitfalls to Avoid
- Failing to consider geographic exposure in returning travelers
- Overlooking medication causes
- Inadequate follow-up of persistent eosinophilia
- Missing clonal disorders that require specific targeted therapy
- Neglecting assessment for end-organ damage, which can lead to significant morbidity and mortality
Remember that the goal of therapy is to mitigate eosinophil-mediated organ damage, and treatment intensity should be guided by the severity of eosinophilia and presence of end-organ involvement.