What is the treatment for eosinophilia?

Treatment of Eosinophilia

The treatment of eosinophilia should be directed at the underlying cause, with corticosteroids being the first-line therapy for most forms of idiopathic hypereosinophilic syndrome (HES) and lymphocyte-variant hypereosinophilia. 1, 2

Diagnostic Approach Before Treatment

Before initiating treatment, it's essential to:

• Confirm eosinophilia (>1.5 × 10⁹/L) and determine if it's persistent (>3 months)
• Exclude secondary causes (allergic, parasitic, drug-induced)
• Perform appropriate testing:
  • Complete blood count with differential
  • Peripheral blood smear
  • Comprehensive metabolic panel with liver function tests
  • Molecular testing for tyrosine kinase gene fusions (PDGFRA, PDGFRB)
  • ANCA testing if EGPA (eosinophilic granulomatosis with polyangiitis) is suspected
  • Tissue biopsy if organ involvement is suspected 1

Treatment Algorithm Based on Etiology

1. Mild Asymptomatic Eosinophilia (<1.5 × 10⁹/L)

• Watch and wait approach with close follow-up 3, 2

2. Myeloid/Lymphoid Neoplasms with Gene Rearrangements

• For PDGFRA or PDGFRB rearrangements: Imatinib (first-line) 3, 2
• For FGFR1 or PCM1-JAK2: Consider JAK2 and FGFR1 inhibitors (investigational) 2

3. Idiopathic Hypereosinophilic Syndrome (HES)

• First-line: Corticosteroids (prednisone 1 mg/kg/day) 1, 2
• Second-line options:
  • Hydroxyurea
  • Interferon-alfa
  • Mepolizumab (FDA-approved IL-5 antagonist) 2
  • Benralizumab (IL-5 receptor antibody, investigational) 2

4. Lymphocyte-Variant Hypereosinophilia

• First-line: Corticosteroids 1, 3, 2

5. Eosinophilic Esophagitis

• First-line: Proton pump inhibitors twice daily for 8-12 weeks 1
• Second-line: Topical corticosteroids
• Third-line: Elimination diets under dietitian supervision 1

6. Chronic Eosinophilic Leukemia, Not Otherwise Specified (CEL, NOS)

• Cytotoxic chemotherapy
• Consider hematopoietic stem cell transplantation for aggressive disease 3

7. Parasitic Infections

• Appropriate antiparasitic therapy based on identified pathogen 4

Monitoring and Follow-up

• Regular monitoring of blood counts to confirm resolution
• For persistent unexplained eosinophilia: regular monitoring for end-organ damage
• For eosinophilic esophagitis: endoscopic follow-up after treatment changes
• If eosinophilia persists at ≥1.5 × 10⁹/L for more than 3 months, refer to hematologist 1

Treatment Efficacy and Outcomes

• Corticosteroids have shown efficacy in treating pulmonary eosinophilia, with complete radiological clearing in 65% of episodes and normalization of blood eosinophil counts in 72% of cases 5
• Mepolizumab has demonstrated effectiveness in idiopathic HES 2
• Imatinib shows excellent response in PDGFRA/B-rearranged eosinophilia 3, 2

Potential Complications and Pitfalls

• Untreated persistent eosinophilia can lead to end-organ damage, including endomyocardial fibrosis and thromboembolism 6
• Long-term corticosteroid use may lead to significant side effects
• Failure to identify PDGFRA/B rearrangements may result in missed opportunity for targeted therapy with imatinib
• Normal blood eosinophil count does not exclude tissue eosinophilia 1

By following this structured approach to diagnosis and treatment of eosinophilia, clinicians can effectively manage this condition while minimizing potential complications and improving patient outcomes.