Normal Absolute Eosinophil Count in a 9-Year-Old Girl
The normal absolute eosinophil count (AEC) for a 9-year-old girl is 50–500 cells/μL (0.05–0.5 × 10⁹/L), with eosinophilia defined as AEC >500 cells/μL. 1, 2
Age-Specific Normal Ranges and Classification
- Normal peripheral blood eosinophils range from 50–500 cells/μL across all pediatric age groups, including 9-year-old children. 1
- Eosinophilia severity is classified as:
- Hypereosinophilia is specifically defined as AEC ≥1,500 cells/μL documented on at least two separate occasions at least 4 weeks apart. 5, 6
Evaluation Approach Based on Severity
For Mild Eosinophilia (500–1,500 cells/μL)
Allergic disorders account for approximately 80% of mild eosinophilia in children, making this the primary diagnostic consideration. 4
History and Physical Examination Focus:
- Document presence of atopic dermatitis, allergic rhinitis, asthma, or food allergies, as 50–80% of children with eosinophilia have concurrent atopic conditions. 7, 8
- Obtain detailed travel history focusing on: fresh water exposure in Africa/tropical regions, consumption of raw/undercooked meat, and timing of travel relative to eosinophilia onset, as helminth infections account for 19–80% of cases in travelers. 9
- Review all current and recent medications, particularly antibiotics like nitrofurantoin, as drug reactions are a frequent non-infectious trigger. 9
- Assess for gastrointestinal symptoms (dysphagia, food impaction, abdominal pain), as these may indicate eosinophilic esophagitis, though peripheral eosinophilia occurs in only 10–50% of pediatric cases. 9, 8
Initial Laboratory Workup:
- Confirm absolute eosinophil count (not just percentage) on repeat testing to establish persistence. 1, 2
- For any travel history to endemic areas: obtain three separate concentrated stool specimens for ova and parasites, Strongyloides serology and culture, and Schistosomiasis serology if fresh water exposure occurred. 9
- Consider aeroallergen sensitivity testing (skin prick or specific IgE) to identify trigger allergens, as this is recommended in atopic children. 9
For Moderate Eosinophilia (1,500–5,000 cells/μL)
Allergy alone rarely produces AEC ≥1,500 cells/μL, mandating comprehensive infectious and immunologic evaluation. 9, 2
Expanded Evaluation:
- Primary immunodeficiencies (PIDs) account for 8.5% of pediatric eosinophilia overall and are the most common cause in severe cases, particularly in regions with high consanguinity rates. 4
- Complete infectious workup is mandatory: stool ova/parasite studies, Strongyloides serology, Schistosomiasis serology, and consideration of empirical treatment with albendazole 400 mg plus ivermectin 200 μg/kg if helminth exposure is suspected and results are pending. 9
- Screen for end-organ damage:
- Cardiac: ECG, troponin, NT-proBNP (chest pain, dyspnea, heart failure symptoms require urgent evaluation) 9
- Pulmonary: chest X-ray, pulmonary function tests (persistent cough, wheezing, infiltrates) 9
- Neurologic: assess for altered mental status, focal deficits, peripheral neuropathy 9
- Gastrointestinal: if dysphagia present, perform upper endoscopy with ≥6 biopsies (2–3 proximal, 2–3 distal esophagus) 9
Hematology Referral Criteria:
- Refer to hematology if eosinophilia persists >3 months after infectious causes have been excluded or treated, as primary eosinophilic disorders require specialized evaluation including bone marrow biopsy and molecular testing for tyrosine kinase fusions. 9
For Severe Eosinophilia (≥5,000 cells/μL)
Severe eosinophilia carries significant risk of morbidity and mortality from end-organ damage and requires urgent comprehensive evaluation. 9
Immediate Actions:
- Urgent assessment for end-organ damage is mandatory, as cardiac, pulmonary, and neurologic injury can occur even before symptoms appear. 9
- Primary immunodeficiencies are the most common etiology in severe pediatric eosinophilia, necessitating immunologic evaluation including immunoglobulin levels, lymphocyte subsets, and functional studies. 4
- Hematologic malignancies must be excluded: peripheral blood smear, bone marrow biopsy, cytogenetics, FISH, and molecular testing for PDGFRA/PDGFRB/FGFR1 rearrangements (critical because PDGFRA/B-positive cases respond dramatically to imatinib). 9
Critical Pitfalls to Avoid
- Do not rely on eosinophilia alone to screen for helminth infection, as many infected children have normal eosinophil counts; only tissue-invasive helminths cause eosinophilia. 9
- Do not wait for symptoms before investigating persistent moderate-to-severe eosinophilia, as subclinical end-organ damage may already be present. 9
- Do not use peripheral eosinophil counts alone to diagnose eosinophilic esophagitis; tissue biopsy showing ≥15 eosinophils per 0.3 mm² is the gold standard. 7, 9
- In Loa loa infection, never use diethylcarbamazine if microfilariae are present on blood film, as it can cause fatal encephalopathy; use corticosteroids with albendazole first to reduce microfilarial load. 9
- Do not overlook Strongyloides infection, as it can persist lifelong and cause fatal hyperinfection syndrome in immunocompromised patients. 9
Monitoring and Follow-Up
- For mild eosinophilia with identified allergic cause and no organ involvement: monitor eosinophil counts every 3–6 months while optimizing atopic disease control. 9
- For moderate-to-severe eosinophilia: regular clinic visits every 3–6 months to assess symptoms, treatment adherence, and adverse effects. 9
- Consider seasonal variation: pollen exposure can increase eosinophil counts in atopic children, particularly during spring/summer. 7, 9
- Median duration of eosinophilia in pediatric cohorts is 7 months overall, shortest in severe cases (2 months), highlighting the importance of persistent monitoring. 4