What is the treatment for a high eosinophil count?

Treatment for High Eosinophil Count

The treatment of high eosinophil count should be guided by the underlying cause, with corticosteroids (such as prednisone 1 mg/kg/day) being the first-line treatment for idiopathic hypereosinophilic syndrome (HES), while targeted therapies should be used for specific molecular variants. 1

Diagnostic Approach Before Treatment

Before initiating treatment, it's essential to determine the cause of eosinophilia:

1. Initial workup:

   • 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 1

2. Classification of severity:

   • Mild: 0.5-1.5 × 10⁹/L
   • Moderate: 1.5-5.0 × 10⁹/L
   • Severe: >5.0 × 10⁹/L 1

3. Key history elements:

   • Travel history (helminth infections)
   • Medication history (NSAIDs, beta-lactam antibiotics)
   • Allergy/atopy history
   • Symptoms of organ involvement 1

Treatment Algorithm

1. Secondary/Reactive Eosinophilia

• Parasitic infections:

  • Empiric treatment with albendazole 400 mg twice daily for 3 days for returning travelers
  • Specific treatments for Strongyloides (ivermectin), Schistosomiasis, and liver flukes 1

• Medication-induced:

  • Discontinue the offending medication 1

• Allergic/atopic conditions:

  • Treat the underlying condition
  • Consider sodium cromoglycate, montelukast, or antihistamines for symptom management 1

2. Eosinophilic Esophagitis (EoE)

• First-line: Proton pump inhibitor therapy twice daily for 8-12 weeks
• Second-line: Topical steroids
• Alternative: Dietary therapy for refractory cases 1
• Monitoring: Histological response with remission defined as <15 eosinophils/0.3 mm² and deep/complete remission as <5 eosinophils/0.3 mm² 2

3. Idiopathic Hypereosinophilic Syndrome (HES)

• First-line: Corticosteroids (prednisone 1 mg/kg/day) 1
• Steroid-sparing agents:
  • Hydroxyurea
  • Interferon-α
  • Mepolizumab (IL-5 antagonist) - recently FDA-approved for idiopathic HES 1, 3

4. Clonal/Myeloproliferative Variants

• PDGFRA or PDGFRB rearrangements: Imatinib (highly effective) 1, 3
• Other molecular variants: Targeted therapy based on specific findings 1
• Chronic eosinophilic leukemia, NOS: Cytotoxic agents, interferon-α 3

Monitoring and Follow-up

• Mild, transient eosinophilia: Follow-up CBC to confirm resolution
• Persistent unexplained eosinophilia: Regular monitoring for end-organ damage
• Persistent eosinophilia ≥1.5 × 10⁹/L for >3 months: Referral to hematologist for further evaluation 1

Novel Therapies Under Investigation

• Anti-IL-5 receptor antibody: Benralizumab
• Other biologics: Dupilumab
• Targeted inhibitors: JAK2 and FGFR1 inhibitors 1, 3

Important Considerations and Pitfalls

• Exclude strongyloidiasis before starting corticosteroids to prevent hyperinfection syndrome 1

• End-organ damage assessment is critical as it determines treatment urgency 1

• Common diagnostic pitfalls:

  • Failing to consider geographic exposure
  • Overlooking medication causes
  • Inadequate follow-up
  • Missing clonal disorders 1

• Treatment goal: Mitigate eosinophil-mediated organ damage rather than just normalizing blood counts 3

For patients with milder forms of eosinophilia (<1.5 × 10⁹/L) without symptoms or signs of organ involvement, a watch and wait approach with close follow-up may be appropriate 3.