What is the approach to managing eosinophilia in pediatric patients?

Approach to Pediatric Eosinophilia

Begin by determining the absolute eosinophil count (AEC) and assessing for life-threatening end-organ damage, as any patient with evidence of end-organ involvement requires urgent medical assessment regardless of eosinophil count. 1

Initial Classification and Risk Assessment

Classify eosinophilia severity:

• Mild: 500-1,500 cells/μL 2, 3
• Moderate: 1,500-5,000 cells/μL 2
• Severe: ≥5,000 cells/μL 2, 3
• Hypereosinophilia: ≥1,500 cells/μL on at least two consecutive tests with minimum 4-week interval 2, 4

Immediately assess for cardiac involvement (Löeffler endocarditis), which presents with myocardial fibrosis, systemic thromboembolism, and acute heart failure—the primary cause of mortality in hypereosinophilic syndromes. 1 Eosinophilic myocarditis progresses through necrotic, thrombotic, and fibrotic stages, with high thromboembolism risk in the thrombotic stage. 1

Systematic Etiologic Evaluation

The most common causes follow the "APLV" mnemonic:

• Allergic disorders (most common overall, 80% of cases) 2, 3
• Parasitic infections 2
• Leukemia/Lymphomas and solid tumors 2
• Vasculitis and Immunodeficiency diseases 2

Severity-Based Diagnostic Approach

For mild eosinophilia (500-1,500 cells/μL):

• Allergic diseases are the predominant cause (80%), including atopic dermatitis and food allergies 3, 5
• Food allergy is an independent risk factor for childhood eosinophilia 3
• Malignancies and rheumatic diseases can present with mild eosinophilia, so do not dismiss based on severity alone 3

For moderate eosinophilia (1,500-5,000 cells/μL):

• Continue to prioritize allergic diseases 3
• Evaluate for parasitic infections, particularly in travelers or migrants (19-80% diagnosis rate) 1
• Consider primary immunodeficiencies (PIDs), especially in regions with consanguineous marriages 3

For severe eosinophilia (≥5,000 cells/μL):

• Primary immunodeficiencies become the most common etiology 3
• PIDs are an independent risk factor for childhood eosinophilia 3
• Values >20,000 cells/μL are highly suggestive of myeloproliferative disorders 2
• Median duration of eosinophilia is shortest in severe cases (2 months) 3

Critical Parasitic Infections to Identify

Helminths are the most common identifiable cause in returning travelers or migrants. 1

Strongyloides stercoralis requires specific attention because it can persist lifelong and present as hyperinfection syndrome with high mortality in immunocompromised patients. 1 Testing for eosinophilia alone is inadequate screening—many infected patients do not have eosinophilia. 1

Schistosoma haematobium is associated with squamous cell bladder carcinoma. 1

For asymptomatic eosinophilia in children >24 months: empirical treatment with albendazole 400 mg single dose plus ivermectin 200 μg/kg single dose is recommended. 1

Diagnostic Workup Algorithm

Step 1: Detailed history focusing on:

• Atopic conditions (eczema, asthma, food allergies) 3, 5
• Travel history and geographic exposures 1
• Medication exposures 4
• Family history of immunodeficiency or consanguinity 3
• Symptoms of organ involvement (cardiac, pulmonary, cutaneous) 2

Step 2: Laboratory evaluation:

• Complete blood count with differential on at least two occasions 4 weeks apart 2, 4
• Stool examination for ova and parasites (multiple samples) 1
• Strongyloides serology 1
• IgE levels and allergen-specific testing if allergic disease suspected 3
• Immunologic workup if PID suspected 3

Step 3: Organ damage assessment:

• Echocardiography and cardiac MRI for cardiac involvement (myocardial biopsy is gold standard) 1
• Pulmonary function tests if respiratory symptoms 2
• Skin examination for dermatologic manifestations 2

Referral Criteria

Refer to hematology if:

• Eosinophilia ≥1,500 cells/μL persists for >3 months after infectious causes are excluded or treated 1
• Severe eosinophilia (≥5,000 cells/μL) without clear secondary cause 3
• Evidence of end-organ damage at any eosinophil level 1

Common Pitfalls to Avoid

Do not delay treatment in patients with end-organ damage—this is a medical emergency requiring prompt aggressive therapy to reduce morbidity and mortality. 1

Do not rely solely on eosinophil count to exclude serious pathology—malignancies and rheumatic diseases frequently present with mild eosinophilia. 3

Do not assume single etiology—hypereosinophilia may be the combinatorial effect of multiple etiologies rather than a single cause, requiring long-term follow-up. 6

Do not overlook primary immunodeficiencies, particularly in children from regions with high rates of consanguineous marriages, as PIDs are not rare causes of severe eosinophilia. 3

Monitoring Strategy

For persistent hypereosinophilia (≥1,500 cells/μL):

• Regular clinic visits to assess symptoms, compliance, and adverse effects 7
• Serial cardiac imaging if cardiac involvement was present 1
• Repeat eosinophil counts every 4 weeks until etiology established 4
• Long-term follow-up as eosinophilia may evolve or reveal additional etiologies over time 6