What is the appropriate treatment for eosinophilia?

Treatment of Eosinophilia

The appropriate treatment for eosinophilia depends critically on identifying the underlying cause: for asymptomatic patients with travel history to endemic regions, empiric antiparasitic therapy with albendazole 400 mg single dose plus ivermectin 200 μg/kg single dose is recommended, while eosinophilic esophagitis requires proton pump inhibitor therapy twice daily for 8-12 weeks or topical steroids. 1, 2

Initial Diagnostic Approach

Before initiating treatment, determine the underlying etiology by:

• Obtaining detailed travel history to identify potential parasitic infections, particularly to tropical or subtropical regions 1, 2
• Performing stool microscopy and serology for helminth infections based on geographic exposure 1
• Evaluating for gastrointestinal symptoms that may indicate eosinophilic esophagitis, requiring endoscopy with at least six biopsies from different esophageal sites 2
• Assessing for end-organ damage (heart, lungs, central nervous system) which requires urgent medical evaluation 1

Treatment Algorithm by Etiology

Parasitic Infections (Most Common in Travelers)

For asymptomatic eosinophilia in patients >24 months with travel history:

• Albendazole 400 mg single dose PLUS ivermectin 200 μg/kg single dose 1, 2

For specific parasitic infections:

• Strongyloidiasis: Ivermectin 200 μg/kg daily for 2 days 1, 2
• Schistosomiasis: Praziquantel 40 mg/kg in two divided doses for 1 day 1, 2
• Ascariasis/Hookworm: Albendazole 400 mg single dose 2
• Loeffler's syndrome (larval migration): Empirical albendazole 400 mg twice daily for 3 days when investigations are negative 3

Critical warning for filarial infections: Seek specialist input before using diethylcarbamazine (DEC) in patients from regions co-endemic for onchocerciasis or with Loa loa microfilaraemia >1000/ml, as severe reactions including encephalopathy and blindness can occur 3, 1

Eosinophilic Esophagitis

First-line pharmacologic options (choose one):

• Proton pump inhibitor therapy twice daily for 8-12 weeks before assessing histological response 3, 1, 2

  • Effective for inducing both histological and clinical remission 3
  • Appears effective for maintaining remission in responders 3

• Topical steroids are highly effective for inducing histological and clinical remission 3, 1, 2

  • Maintenance treatment should be recommended after clinical review, as relapse rates are high after withdrawal 3

Dietary management:

• Two-food elimination diet (milk +/- wheat or egg) for 8-12 weeks with mandatory dietitian support 1, 2
• Allergy testing (skin prick, specific IgE, patch testing) is NOT recommended for choosing dietary therapy 3
• Exclusive elemental diets have high efficacy but low compliance; reserve for refractory cases 3

Medications NOT recommended:

• Immunomodulators (azathioprine, 6-mercaptopurine) 3
• Anti-TNF and anti-integrin therapies 3
• Sodium cromoglycate, montelukast, and antihistamines (though may help concomitant atopic disease) 3

Pulmonary Eosinophilia Syndromes

Tropical pulmonary eosinophilia (W. bancrofti, B. malayi):

• Diethylcarbamazine with specialist guidance (see warning above) 3
• Symptoms typically resolve rapidly; 20% relapse rate necessitating re-treatment 3
• Steroids may be used for ongoing alveolitis and pulmonary fibrosis (exclude strongyloidiasis first) 3

Paragonimiasis:

• Seek expert advice regarding doxycycline and diethylcarbamazine 3
• Corticosteroids may prevent pulmonary fibrosis 3
• Bronchodilators for dyspnea 3

Pulmonary hydatid disease:

• Requires specialist center management 3
• Primarily surgical with complete excision 3
• Praziquantel pre- and post-operatively, plus prolonged albendazole post-operatively 3

Hypereosinophilic Syndrome and Primary Eosinophilias

For persistent eosinophilia ≥1.5 × 10⁹/L for >3 months without organ damage:

• Refer to hematologist for evaluation of clonal/neoplastic causes 1

For mild eosinophilia (<1.5 × 10⁹/L) without organ involvement:

• Watch and wait approach with close follow-up 4, 5

For PDGFRA or PDGFRB rearrangements:

• Imatinib is the treatment of choice due to exquisite responsiveness 4, 5

For lymphocyte-variant hypereosinophilia and idiopathic HES:

• Corticosteroids are first-line therapy 4, 5
• Hydroxyurea and interferon-alpha for steroid-refractory cases 4, 5

Monitoring Treatment Response

• Obtain follow-up eosinophil counts after antiparasitic treatment to assess response 1
• For eosinophilic esophagitis: Repeat endoscopy with biopsy while on treatment to assess histological response 3, 2
  • Histological remission defined as <15 eosinophils per 0.3 mm² 1, 2
• If symptoms recur during treatment: Repeat endoscopy for assessment and histology 3

Management of Refractory Cases

• Joint management by gastroenterologist and allergist for eosinophilic esophagitis refractory to treatment or with significant concomitant atopic disease 3, 2
• Novel biologics (dupilumab, cendakimab, benralizumab) show promise but have low-quality evidence 3
• For persistent eosinophilia despite treatment: Refer to hematologist for further investigation 1

Critical Pitfalls to Avoid

• Do not rely on eosinophilia alone to screen for helminth infection - many infected individuals have normal eosinophil counts 1
• Never use diethylcarbamazine without excluding onchocerciasis co-infection in patients from endemic regions 3, 1
• Do not assume symptom resolution equals histological remission in eosinophilic esophagitis - endoscopic confirmation is required 2, 6
• Recognize that persistent eosinophilia of any degree can cause end-organ damage (heart, lungs, CNS) requiring urgent assessment 1
• Monitor for Candida infection in patients on topical steroids for eosinophilic esophagitis; treat with topical antifungals while continuing steroids 3