What is the appropriate treatment for elevated eosinophil (Eos) counts?

Treatment for Elevated Eosinophils

The appropriate treatment for elevated eosinophil counts depends critically on identifying the underlying cause through systematic evaluation, with treatment ranging from empiric antiparasitic therapy for mild eosinophilia with travel history, to topical steroids or dietary elimination for eosinophilic esophagitis, to imatinib for PDGFRA/PDGFRB-rearranged disease, to corticosteroids for hypereosinophilic syndrome. 1

Initial Diagnostic Evaluation

Before initiating treatment, determine the degree and cause of eosinophilia:

Classify by Severity

• Mild eosinophilia (500-1500 cells/μL): Most commonly due to allergic disorders including asthma, allergic rhinitis, and atopic dermatitis 2
• Moderate eosinophilia (1500-5000 cells/μL): Consider eosinophilic esophagitis, parasitic infections, or drug reactions 2
• Hypereosinophilia (>1500 cells/μL sustained): Requires evaluation for primary (clonal) versus secondary (reactive) causes 3, 4

Essential Workup Components

• Travel and exposure history: Assess for parasitic infections, particularly in patients with travel to endemic areas 1
• Gastrointestinal symptoms: If dysphagia or food impaction present, perform endoscopy with at least 6 biopsies from 2 different esophageal sites 5
• Atopic history: Evaluate for allergic rhinitis, asthma, and atopic dermatitis, which are present in 50-80% of eosinophilic esophagitis patients 6
• Stool studies: Obtain stool microscopy and serology for helminth infections based on exposure history 1
• Hematologic evaluation: For persistent eosinophilia ≥1.5 × 10⁹/L for >3 months, refer to hematology for bone marrow evaluation, cytogenetics, and molecular testing for PDGFRA/PDGFRB rearrangements 1, 3

Critical pitfall: Peripheral blood eosinophil counts may not correlate with tissue eosinophilia, particularly in eosinophilic esophagitis where tissue biopsy remains the gold standard 5, 2

Treatment Algorithm by Etiology

For Parasitic Infections

• First-line empiric therapy for returning travelers with asymptomatic eosinophilia: Albendazole 400 mg single dose PLUS ivermectin 200 μg/kg single dose 1, 5
• Strongyloidiasis: Ivermectin 200 μg/kg daily for 1-2 days 1
• Schistosomiasis: Praziquantel 40 mg/kg in two divided doses for 1 day 1
• Follow-up: Obtain repeat eosinophil counts after treatment to assess response 1, 5

Important caveat: Many helminth-infected patients do not have eosinophilia, so absence of eosinophilia does not exclude parasitic infection 1

For Eosinophilic Esophagitis

The diagnosis requires >15 eosinophils per high-power field (0.3 mm²) on esophageal biopsy in the proper clinical context 6, 5

Treatment Options (in order of preference):

1. Proton pump inhibitor trial: Twice-daily dosing for 8-12 weeks as initial therapy 1
2. Topical corticosteroids: Decrease blood eosinophil counts in 88% of patients 5, 2
3. Dietary elimination: Two-food elimination diet (milk +/- wheat or egg) for 8-12 weeks with dietitian support 1, 5

Target for remission: <15 eosinophils per 0.3 mm² (histological remission) or <5 eosinophils per 0.3 mm² (deep remission) 5

Critical pitfall: Allergy testing to foods is NOT recommended for choosing dietary restriction therapy 1, 5

For Primary Eosinophilic Disorders

PDGFRA/PDGFRB-Rearranged Disease

• Imatinib is the treatment of choice due to exquisite responsiveness of these molecular subtypes 3, 4, 7
• Identification of these rearrangements is critical and requires cytogenetic and molecular testing 3, 4

Hypereosinophilic Syndrome (HES) and Idiopathic Eosinophilia

• First-line therapy: Corticosteroids 1, 3, 4, 7
• Second-line options for steroid-refractory cases:
  • Hydroxyurea 3, 4
  • Interferon-α 3, 4, 7
  • Mepolizumab (anti-IL-5 antibody, FDA-approved for idiopathic HES) 3

Watch and wait approach: For patients with eosinophilia <1.5 × 10⁹/L without symptoms or organ involvement, close follow-up without immediate treatment is appropriate 3, 4

For Concomitant Atopic Disease

• Optimize treatment for allergic rhinitis, asthma, and atopic dermatitis 5
• Consider sodium cromoglycate, montelukast, and antihistamines for atopic conditions, though these are NOT recommended for primary management of eosinophilic esophagitis 6
• For refractory cases with significant atopic disease, consider joint management with allergy specialist 5

Emerging Therapies (Not Yet Standard)

The 2022 British Society of Gastroenterology guidelines note promising but not yet recommended therapies 6:

• Dupilumab (anti-IL-4 receptor): Showed significant reduction in eosinophil counts and improved esophageal distensibility in phase 2 trials 6
• Cendakimab (anti-IL-13): Demonstrated reduction in eosinophil counts and dysphagia scores in phase 2 trials 6
• Benralizumab (anti-IL-5 receptor): Effective in eosinophilic asthma with case reports of resolution in eosinophilic esophagitis 6

These agents may be considered for patients with coexisting allergic diseases pending further trial data 6

Monitoring and Follow-Up

• Repeat eosinophil counts after treatment to assess response 1, 5
• For eosinophilic esophagitis: If symptoms recur on treatment, repeat endoscopy with histology 6, 5
• For persistent unexplained eosinophilia: Refer to hematology for evaluation of clonal disorders 1
• Organ damage surveillance: Persistent eosinophilia can cause significant end-organ damage, particularly affecting heart, lungs, and central nervous system 1