In a patient with poorly controlled asthma, multiple exacerbations, elevated eosinophil count, normal IgE, and Southeast Asian origin, what are the concerns?

Primary Concern: Rule Out Parasitic Infection (Helminthiasis)

In a Southeast Asian patient with poorly controlled asthma, multiple exacerbations, and elevated eosinophils but normal IgE, the most critical concern is parasitic infection—particularly helminthic infections such as Strongyloides stercoralis, which can cause life-threatening hyperinfection syndrome if treated with corticosteroids. 1

Immediate Diagnostic Priorities

1. Helminth Screening is Mandatory

The combination of Southeast Asian origin and peripheral eosinophilia creates a high pre-test probability for parasitic infection 1. Key helminth infections to exclude include:

• Strongyloides stercoralis (most critical—can persist >50 years and cause fatal hyperinfection with immunosuppression)
• Hookworm species
• Ascaris lumbricoides
• Schistosomiasis (if freshwater exposure history)

Critical testing sequence:

• Concentrated stool microscopy for ova, cysts, and parasites (minimum 3 samples on different days)
• Strongyloides serology (becomes positive 4-12 weeks post-infection)
• Consider stool PCR if available
• Schistosoma serology if relevant exposure history 1

2. Timing Considerations for Testing

A crucial pitfall: eosinophilia may be transient during the tissue migration phase of helminth infection, occurring during the pre-patent period when stool microscopy is still negative 1. If initial stool samples are negative but clinical suspicion remains high, repeat testing in 4-12 weeks when serology becomes positive.

Secondary Concern: Eosinophilic Asthma Phenotype

Phenotype Classification

This patient likely has T2-high eosinophilic asthma rather than allergic asthma, given:

• Normal IgE (argues against IgE-mediated allergic asthma)
• Elevated eosinophils
• Poor control despite conventional therapy 2

The normal IgE is a key distinguishing feature: Patients with T2-high asthma can have upregulated IL-13 targets, increased bronchial hyperresponsiveness, and eosinophilia WITHOUT elevated IgE levels 2. This represents the intrinsic (eosinophilic) form of asthma, typically adult-onset, where eosinophils are disease drivers rather than bystanders 3.

Biomarker Assessment Strategy

Once parasitic infection is excluded:

• Blood eosinophil count is the primary biomarker for treatment decisions 4

  • Levels ≥300 cells/μL predict increased exacerbation risk 5
  • Persistent elevation indicates ongoing T2 inflammation requiring escalation

• Fractional exhaled nitric oxide (FeNO) adds prognostic value 5

  • FeNO ≥50 ppb combined with eosinophils ≥300 cells/μL identifies highest exacerbation risk
  • The combination has greater predictive value than either biomarker alone

• Induced sputum eosinophils (if available) provide the most direct assessment of airway inflammation and predict corticosteroid responsiveness 4

Treatment Algorithm After Parasitic Exclusion

Step 1: Optimize Conventional Therapy

Before considering biologics, verify:

• Adherence to inhaled corticosteroids (ICS) 6
• Proper inhaler technique
• Environmental trigger control
• Treatment of comorbidities (rhinosinusitis, GERD)

Step 2: Consider Biologic Therapy

For steroid-refractory eosinophilic asthma with persistent eosinophilia despite high-dose ICS:

Anti-IL-5/IL-5R biologics are the preferred choice given normal IgE 2:

• Mepolizumab (anti-IL-5)
• Benralizumab (anti-IL-5 receptor)

These agents reduce circulating and sputum eosinophils and achieve approximately 50% reduction in exacerbations in patients with steroid-refractory eosinophilic disease 2.

Omalizumab (anti-IgE) is NOT appropriate given normal IgE levels—this patient does not have the allergic phenotype where omalizumab is effective 6.

Critical Safety Warnings

Never Escalate Corticosteroids Before Excluding Strongyloides

Systemic corticosteroids in a patient with undiagnosed Strongyloides can trigger hyperinfection syndrome with mortality rates approaching 70-90% 1. This is particularly relevant since:

• The patient has multiple exacerbations (likely received oral corticosteroid bursts)
• Strongyloides can remain dormant for decades
• Southeast Asian origin is a major risk factor

Monitor for Eosinophilic Granulomatosis with Polyangiitis (EGPA)

While less likely, the combination of asthma, eosinophilia, and potential multi-organ involvement warrants consideration of EGPA, especially if the patient develops 7:

• Peripheral neuropathy (mononeuritis multiplex pattern)
• Skin lesions (palpable purpura)
• Cardiac involvement
• Renal manifestations
• ENT symptoms (chronic rhinosinusitis with nasal polyps)

Practical Management Sequence

1. Immediately obtain: Stool ova and parasites (×3), Strongyloides serology, complete travel/exposure history
2. Hold or minimize systemic corticosteroids until parasitic infection excluded
3. Measure FeNO and document blood eosinophil trends over time
4. If helminth-positive: Treat appropriately (ivermectin for Strongyloides), then reassess asthma control
5. If helminth-negative and eosinophils persistently ≥300 cells/μL: Consider anti-IL-5/IL-5R biologic therapy
6. Monitor treatment response at 8-12 weeks using symptoms, chest imaging, and ≥20% reduction in eosinophil count 8

The geographic origin combined with eosinophilia creates a diagnostic imperative that supersedes asthma management until life-threatening parasitic infection is definitively excluded.