What is the appropriate management for a 10-year-old patient with elevated absolute eosinophils (EOS) and absolute basophils (BASO) on a differential lab test?

Management of a 10-Year-Old with Elevated Eosinophils and Basophils

Begin with a systematic evaluation focusing on allergic disorders and parasitic infections as the most likely causes, followed by assessment for primary immunodeficiencies if initial workup is unrevealing, as these represent the predominant etiologies in pediatric eosinophilia. 1, 2

Initial Clinical Assessment

Obtain a detailed history focusing on:

• Gastrointestinal symptoms (dysphagia, vomiting, abdominal pain, feeding difficulties) which may indicate eosinophilic esophagitis, particularly common at age 10 years 3
• Atopic conditions including asthma, allergic rhinitis, atopic dermatitis, and food allergies 1, 2
• Travel history to endemic areas for parasitic infections 1
• Consanguinity in the family, which increases risk for primary immunodeficiencies 2
• Duration of eosinophilia (shorter duration <2 months suggests more severe underlying pathology) 2

Severity Classification and Risk Stratification

Classify the eosinophilia level to guide workup intensity:

• Mild: 500-1,500 cells/μL (most commonly allergic diseases) 4, 2
• Moderate: 1,500-5,000 cells/μL (allergic diseases or primary immunodeficiencies) 4, 2
• Severe: >5,000 cells/μL (primary immunodeficiencies most common; values >20,000 cells/μL highly suggestive of myeloproliferative disorders) 4, 2

Note: Basophil elevation alongside eosinophilia may suggest a myeloproliferative process, though this is rare in children. 4

Diagnostic Algorithm

For Mild to Moderate Eosinophilia (500-5,000 cells/μL):

Step 1: Evaluate for allergic diseases (80% of cases) 2

• Assess for food allergies, which are an independent risk factor for childhood eosinophilia (OR: 1.866) 2
• Screen for allergic rhinitis, asthma, and atopic dermatitis 1
• Consider aeroallergen sensitivity testing given 50-80% prevalence in eosinophilic conditions 1

Step 2: If gastrointestinal symptoms present:

• Perform upper endoscopy with multiple biopsies (minimum 6 biopsies from at least 2 different esophageal sites) to evaluate for eosinophilic esophagitis 3, 1, 5
• Diagnostic threshold: ≥15 eosinophils per 0.3 mm² (or per high-power field) 3, 5
• Children at age 10 typically present with abdominal pain or dysphagia 3
• Critical caveat: 21% of children with eosinophilic esophagitis have macroscopically normal esophagus on endoscopy 3

Step 3: Screen for parasitic infections:

• Stool microscopy for ova and parasites (three samples) 1
• Serology for specific helminth infections based on travel history 1
• Consider empiric treatment with albendazole 400 mg single dose plus ivermectin 200 μg/kg single dose for returning travelers 1

Step 4: If above negative, evaluate for primary immunodeficiencies:

• Primary immunodeficiencies are an independent risk factor (OR: 2.200) and not rare in pediatric eosinophilia, especially with consanguinity 2
• Obtain immunoglobulin levels, lymphocyte subsets, and consider genetic testing 2

For Severe Eosinophilia (>5,000 cells/μL):

Urgent evaluation required due to risk of end-organ damage:

• Assess for cardiac involvement (echocardiography), pulmonary involvement (chest imaging, pulmonary function tests), and cutaneous manifestations 4, 6
• Primary immunodeficiencies are the most common cause in severe pediatric eosinophilia 2
• Evaluate for myeloproliferative disorders with bone marrow biopsy and molecular testing (FIP1L1-PDGFRA fusion) 4, 6
• Screen for malignancies (though only 0.8% of cases, they can present with mild eosinophilia) 2

Treatment Approach Based on Etiology

For eosinophilic esophagitis:

• Topical corticosteroids decrease blood eosinophil counts in 88% of patients 1
• Dietary elimination with dietitian support for 8-12 weeks 1
• Target histological remission: <15 eosinophils per 0.3 mm² 1

For parasitic infections:

• Albendazole 400 mg single dose for most helminths 1
• Ivermectin 200 μg/kg single dose for strongyloidiasis 1

For allergic disorders:

• Optimize treatment of underlying atopic conditions 1
• Consider joint management with allergy specialist for refractory cases 1

Monitoring Strategy

Repeat eosinophil count after 4 weeks to confirm persistence (hypereosinophilia definition requires ≥1,500 cells/μL on two consecutive tests at least 4 weeks apart) 4, 7

Follow-up testing:

• Post-treatment eosinophil counts to assess response 1
• Repeat endoscopy if symptoms recur during treatment 1
• Monitor for end-organ damage in severe cases 4, 6

Critical Pitfalls to Avoid

• Do not dismiss mild eosinophilia: Malignancies and rheumatic diseases can present with mild elevations 2
• Do not rely on endoscopic appearance alone: Significant proportion of children with eosinophilic esophagitis have normal-appearing esophagus 3
• Do not overlook primary immunodeficiencies: These are more common than appreciated, particularly in populations with consanguinity 2
• Do not delay evaluation of severe eosinophilia: Risk of cardiac, pulmonary, and cutaneous damage from eosinophil degranulation products 4, 6