What is the treatment approach for eosinophilia?

Treatment Approach for Eosinophilia

The treatment of eosinophilia should be directed at the underlying cause, with corticosteroids serving as first-line therapy for most forms of hypereosinophilic syndromes and idiopathic eosinophilia. 1, 2

Diagnostic Evaluation Before Treatment

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

1. Rule out secondary causes:

   • Parasitic infections (particularly helminth infections)
   • Medication reactions
   • Allergic disorders
   • Autoimmune conditions

2. Diagnostic workup:

   • Complete blood count with differential
   • Concentrated stool microscopy for all patients returning from tropical regions 1
   • Serology for specific parasites based on travel/exposure history
   • Bone marrow examination with cytogenetics for suspected hematologic disorders
   • Testing for PDGFRA, PDGFRB, or FGFR1 rearrangements in suspected myeloproliferative variants 2

Treatment Algorithm Based on Etiology

1. Parasitic Infections

• Helminth infections:
  • Albendazole 400 mg daily for 3 days (mild disease) 1
  • For specific parasites:
    • Schistosomiasis: Praziquantel 40 mg/kg as single dose (repeat at 6-8 weeks) 1
    • Strongyloidiasis: Ivermectin
    • Hookworm/Ascaris: Albendazole 400 mg single dose 1

2. Hypereosinophilic Syndromes (HES)

• Myeloid neoplasms with PDGFRA or PDGFRB rearrangements:

  • Imatinib - first-line therapy due to excellent response 2, 3

• Idiopathic HES and Lymphocyte-variant HES:

  • First-line: Corticosteroids (prednisone 1 mg/kg/day initially, with taper based on response) 2, 3
  • Second-line options for steroid-refractory cases:
    • Hydroxyurea
    • Interferon-alpha
    • Cytotoxic agents for aggressive disease 2, 3

• Novel biologic therapies:

  • Anti-IL-5 antibodies (mepolizumab) have shown efficacy in case reports 1, 2
  • Anti-IL-5 receptor antibodies (benralizumab) are under investigation 2
  • These biologics await further clinical trials and are not recommended for routine use 1

3. Eosinophilic Esophagitis (EoE)

• Dietary approach: Elimination diets to identify and remove food triggers 1
• Pharmacologic approach: Topical corticosteroids (fluticasone or budesonide) 1
• Proton pump inhibitors: May be effective in some patients with EoE 4

Monitoring and Treatment Endpoints

• Regular monitoring of eosinophil counts is essential
• Treatment should initially aim at improving symptoms 1
• For persistent eosinophilia, decisions to advance treatment should consider:
  • Degree of symptoms
  • Age of patient
  • Presence of organ damage
  • Patient preferences 1

Special Considerations

• Asymptomatic mild eosinophilia (<1.5 × 10^9/L): Watch and wait approach with close follow-up may be appropriate 2, 3
• Severe eosinophilia with organ involvement: Requires prompt treatment to prevent irreversible damage 5
• Tropical pulmonary eosinophilia: Diethylcarbamazine is the treatment of choice 1

Pitfalls and Caveats

• Failure to identify and treat underlying parasitic infections can lead to persistent eosinophilia
• Corticosteroid treatment before ruling out strongyloidiasis can lead to hyperinfection syndrome
• Long-term corticosteroid use carries significant side effects; steroid-sparing agents should be considered for maintenance therapy
• Patients with eosinophilia are at increased risk for thromboembolism and should be monitored accordingly
• The natural history of untreated eosinophilia is not well established, making treatment decisions challenging in asymptomatic patients 1