What is the best course of treatment for a patient with elevated eosinophils (eosinophilia) related to a lung cause, suspected to have eosinophilic pneumonia or acute respiratory distress syndrome?

Management of Elevated Eosinophils Related to Lung Causes

For patients with pulmonary eosinophilia, corticosteroids are the definitive first-line treatment and should be initiated urgently in symptomatic cases, as delayed treatment can lead to fatal lung disease, particularly in acute eosinophilic pneumonia. 1

Immediate Assessment for Life-Threatening Complications

Before initiating treatment, you must urgently evaluate for end-organ damage that determines both prognosis and treatment intensity:

• Cardiac involvement (chest pain, dyspnea, heart failure, arrhythmias) requires immediate ECG, troponin, NT-proBNP, and echocardiography, as cardiac damage is the primary driver of mortality in hypereosinophilic syndromes 2
• Respiratory failure or acute respiratory distress syndrome necessitates mechanical ventilation support while initiating aggressive corticosteroid therapy 3, 4
• Neurological symptoms (altered mental status, focal deficits, peripheral neuropathy) demand urgent evaluation as eosinophilic meningitis or neuropathy can cause permanent damage 2

Exclude Parasitic Causes Before Corticosteroids

Critical pitfall: Never start corticosteroids before excluding Strongyloides stercoralis, as steroids can precipitate fatal hyperinfection syndrome. 2, 5

Mandatory Pre-Treatment Screening:

• Obtain detailed travel history focusing on fresh water exposure in Africa/tropical regions and raw/undercooked meat consumption 2, 6
• Order three separate concentrated stool specimens for ova and parasites 7, 2
• Send Strongyloides serology and culture immediately 2, 6
• If fresh water exposure in endemic areas: Schistosomiasis serology 2, 6
• For tropical pulmonary eosinophilia specifically: Filarial serology (strongly positive with microfilariae NOT detected on blood film) 7, 5

Empiric Antiparasitic Treatment:

If travel history to endemic areas exists and investigations are pending, empiric treatment with albendazole 400 mg twice daily for 3 days is recommended while awaiting results 7, 6

Corticosteroid Therapy Protocol

For Acute Eosinophilic Pneumonia or Severe Disease:

• High-dose corticosteroids are mandatory and life-saving 1, 4
• Initiate prednisone 0.5-1 mg/kg/day (or equivalent IV methylprednisolone if intubated) 4, 8
• Response is typically dramatic within 24-48 hours 4
• Taper slowly over 2-3 months to prevent relapse 4

For Chronic Eosinophilic Pneumonia:

• Start prednisone 0.5 mg/kg/day for 2 weeks 4
• Taper gradually over 3-6 months based on clinical and radiographic response 4
• Relapses occur frequently (>50% of cases) when tapering or stopping treatment, necessitating prolonged maintenance therapy 4

For Tropical Pulmonary Eosinophilia:

• Diethylcarbamazine (DEC) is the definitive treatment and must be initiated promptly to prevent irreversible pulmonary fibrosis 7, 5
• Before administering DEC, you must exclude Loa loa and Onchocerca volvulus co-infection, as DEC can cause fatal encephalopathy if Loa loa microfilariae are present 2, 5
• If Loa loa microfilariae detected: use corticosteroids with albendazole first to reduce microfilarial load below 1000/ml before giving DEC 2, 5
• Adjunctive corticosteroids (prednisolone 20 mg/day for 5 days initially) may be beneficial for ongoing alveolitis and to prevent pulmonary fibrosis 7, 5
• 20% of patients relapse and require re-treatment with a second DEC course 7, 5

Specific Parasitic Treatments When Identified:

• Strongyloidiasis: Ivermectin 200 μg/kg daily for 2 days 6
• Schistosomiasis: Praziquantel 40 mg/kg as single dose, repeated at 6-8 weeks; add prednisolone 20 mg/day for 5 days in acute Katayama syndrome 7, 6
• Loeffler's syndrome (Ascaris, hookworm): Albendazole 400 mg twice daily for 3 days 7

Diagnostic Confirmation Requirements

While initiating treatment, obtain:

• Chest radiograph to document pulmonary infiltrates (migratory infiltrates suggest Loeffler's syndrome; interstitial/reticulonodular patterns suggest tropical pulmonary eosinophilia) 7
• Pulmonary function tests (obstructive pattern early, restrictive pattern in chronic disease) 7, 5
• Bronchoscopy with bronchoalveolar lavage showing >10% eosinophils confirms pulmonary eosinophilia when diagnosis uncertain 8, 9
• Lung biopsy only if diagnosis remains unclear after less invasive testing 8, 9

Monitoring and Follow-Up

• Repeat eosinophil counts after treatment to assess response 6
• Monitor for treatment-related complications including corticosteroid side effects (hyperglycemia, hypertension, osteoporosis prophylaxis needed) 2
• If eosinophilia ≥1.5 × 10⁹/L persists for >3 months after excluding and treating infectious causes, refer to hematology to evaluate for hypereosinophilic syndrome or myeloid neoplasms 2, 6
• For tropical pulmonary eosinophilia, monitor for relapse with clinical symptoms and eosinophil counts 5

Common Pitfalls to Avoid

• Do not delay corticosteroids in acute eosinophilic pneumonia awaiting parasitic workup results, as this can be fatal; treat empirically for parasites while initiating steroids if travel history warrants 1
• Do not assume normal eosinophil counts exclude helminth infection—many infected patients have normal counts, so test based on exposure history regardless 2
• Do not stop corticosteroids abruptly in chronic eosinophilic pneumonia, as relapse rates exceed 50% 4
• Do not use DEC without excluding Loa loa if patient has been in endemic areas (Central/West Africa), as fatal encephalopathy can result 2, 5