What is the management approach for a 70-year-old female with significantly elevated absolute eosinophils (Absolute Eosinophil Count) and a normal Complete Blood Count (CBC)?

Management of Moderate Eosinophilia in a 70-Year-Old Female

Immediate Clinical Assessment

This patient requires systematic evaluation to identify the underlying cause of moderate eosinophilia (1729 cells/μL), with initial focus on the most common etiologies: parasitic infections, allergic disorders, and gastrointestinal eosinophilic conditions, before considering hematologic causes. 1

Key History Elements to Obtain

• Travel history, particularly to tropical or subtropical regions where helminth infections are endemic 2, 1
• New medications started within the past 6 months, as drug reactions are a common cause 2
• Gastrointestinal symptoms including dysphagia, abdominal pain, nausea, or diarrhea suggesting eosinophilic esophagitis or parasitic infection 2
• Allergic symptoms including asthma, allergic rhinitis, or atopic dermatitis 1, 3
• Skin manifestations such as pruritus, rash, or urticaria 2

Physical Examination Focus

• Palpate for hepatosplenomegaly which may indicate myeloproliferative disorders or parasitic infections 2
• Examine skin for rashes, urticaria, or signs of parasitic infection 2
• Assess for signs of cardiac involvement (murmurs, heart failure) as eosinophilia can cause end-organ damage 4, 5

Diagnostic Workup Algorithm

Initial Laboratory Testing

Order the following tests immediately: 2, 1

• Stool microscopy for ova and parasites (3 separate specimens) to evaluate for helminth infections 2, 1
• Serology for Strongyloides and other parasites based on travel history 2, 1
• Serum tryptase and vitamin B12 levels to screen for myeloproliferative variants (elevated in PDGFRA-associated neoplasms) 2, 4
• Total IgE level (elevated in allergic conditions and lymphocytic variant hypereosinophilic syndrome) 2, 6
• Comprehensive metabolic panel, LDH, and liver function tests 2

Risk Stratification by Eosinophil Count

This patient's count of 1729 cells/μL falls into the moderate eosinophilia category (1500-5000 cells/μL), which warrants investigation but is not immediately life-threatening. 3, 5

• Mild eosinophilia (500-1500 cells/μL): Usually allergic disorders 3
• Moderate eosinophilia (1500-5000 cells/μL): Parasitic infections, eosinophilic esophagitis, drug reactions 3
• Severe eosinophilia (>5000 cells/μL): Consider myeloproliferative disorders, hypereosinophilic syndrome 3

Management Based on Likely Etiologies

If Travel History Positive or High Parasitic Risk

Empiric treatment is reasonable while awaiting test results: 1

• Albendazole 400 mg single dose PLUS Ivermectin 200 μg/kg single dose for returning travelers with asymptomatic eosinophilia 2, 1
• This covers most common helminth infections including hookworm, roundworm, and strongyloidiasis 2
• Recheck eosinophil count in 4-6 weeks to assess response 1

If Gastrointestinal Symptoms Present

Consider eosinophilic esophagitis: 2, 1

• Initiate proton pump inhibitor therapy twice daily for 8-12 weeks as first-line treatment 1
• If symptoms persist, refer for endoscopy with multiple biopsies (minimum 6 biopsies from at least 2 sites in esophagus) 2
• Diagnostic threshold is >15 eosinophils per 0.3 mm² in any biopsy specimen 2

If No Clear Secondary Cause Identified

Monitor for persistence before extensive workup: 5, 7

• Repeat CBC with differential in 4 weeks to determine if eosinophilia persists 1, 8
• If eosinophilia persists ≥1.5 × 10⁹/L for >3 months, refer to hematology for evaluation of hypereosinophilic syndrome 1, 5

When to Refer to Hematology

Immediate hematology referral is indicated if: 2, 5

• Eosinophilia persists >1500 cells/μL for more than 3 months despite treatment 1
• Signs of end-organ damage (cardiac, pulmonary, neurologic, or skin involvement) 4, 5
• Elevated serum tryptase or vitamin B12 suggesting myeloproliferative disorder 2, 4
• Splenomegaly, lymphadenopathy, or other concerning features on examination 2

Hematology workup will include: 2, 5

• Bone marrow biopsy with cytogenetics and FISH for PDGFRA, PDGFRB, FGFR1 rearrangements 2, 5
• Flow cytometry to evaluate for aberrant T-cell populations (lymphocytic variant) 2, 5
• Molecular testing for clonal hematopoiesis 2

Treatment Considerations for Persistent Idiopathic Eosinophilia

If all secondary causes are excluded and eosinophilia persists without organ damage:

• Watch-and-wait approach with close monitoring is appropriate for asymptomatic patients with counts <1500 cells/μL 5, 9
• For idiopathic hypereosinophilic syndrome (diagnosis of exclusion), corticosteroids are first-line therapy 1, 5, 9
• If PDGFRA or PDGFRB rearrangement is identified, imatinib is the treatment of choice with excellent response rates 4, 5, 9

Critical Pitfalls to Avoid

• Do not assume allergic cause without investigation: While allergic disorders are the most common cause of mild eosinophilia, this patient's count exceeds 1500 cells/μL, warranting more thorough evaluation 3, 8
• Peripheral eosinophil counts may not correlate with tissue eosinophilia: Normal blood counts don't exclude eosinophilic esophagitis or other tissue-based disorders 2, 1, 6
• Many helminth infections don't cause eosinophilia: Testing for eosinophilia alone is inadequate screening; direct stool testing is essential 1
• Don't delay cardiac evaluation if symptoms present: Cardiac involvement is the leading cause of morbidity and mortality in hypereosinophilic syndrome 4, 5
• Persistent eosinophilia of any degree can cause end-organ damage: Even moderate elevations warrant monitoring for cardiac, pulmonary, and neurologic complications 1, 4