What are the components and management of Loeffler's syndrome?

Loeffler's Syndrome: Clinical Triad and Management

The Classic Triad

Loeffler's syndrome is defined by three key components: transient migratory pulmonary infiltrates on chest imaging, peripheral blood eosinophilia, and minimal to absent respiratory symptoms. 1

The specific features include:

• Pulmonary infiltrates: Migratory, fleeting infiltrates visible on chest radiograph (present in 95% of cases), appearing as ground-glass opacities or nodules that characteristically move to different lung zones over days to weeks 2, 3

• Peripheral eosinophilia: Marked elevation in blood eosinophils, sometimes exceeding 5 × 10⁹/L, though can occasionally be absent in early presentation 1

• Mild or absent symptoms: Patients typically present with minimal illness—dry cough, wheeze, low-grade fever, and urticarial rash are common when symptoms occur, but many cases are asymptomatic 1, 4

Etiology and Pathophysiology

The syndrome results from larval migration through the lungs during acute helminth infection, occurring during the prepatent period (1-2 weeks post-infection) when larvae transit through pulmonary tissue. 4

Common causative organisms include:

• Ascaris lumbricoides (roundworm) 1, 4
• Hookworm (Ancylostoma duodenale/Necator americanus) 1, 4
• Strongyloides stercoralis 1, 3
• Less commonly: Toxocara, Trichinella, other helminths 5

Non-parasitic causes (less common):

• Drug reactions: penicillin, nitrofurantoin, tricyclic antidepressants 5, 6
• Fungal infections: Aspergillus species 5

Diagnostic Approach

Diagnosis is primarily clinical based on the triad plus travel/exposure history, as stool examinations are typically negative during the prepatent period when symptoms occur. 4

Key diagnostic steps:

• Concentrated stool microscopy (×3 samples on different days) for all returning travelers with eosinophilia, though sensitivity is limited during larval migration phase 1, 4
• Chest imaging: Look for migratory infiltrates, nodules, or ground-glass opacities 1, 2
• Complete blood count: Document degree of eosinophilia 1, 2
• Serology: Strongyloides serology has good diagnostic yield and should be performed in all cases 1
• Sputum examination: Rarely, larvae may be visualized in sputum or bronchoalveolar lavage 4

Treatment Recommendations

First-line empirical treatment during the prepatent period is albendazole 400 mg twice daily for 3 days PLUS ivermectin 200 μg/kg once daily for 3 days, with prednisolone 30 mg daily for 5 days added in severe cases. 4

Standard Treatment Regimens:

For empirical treatment (when specific pathogen unknown):

• Albendazole 400 mg BID × 3 days PLUS ivermectin 200 μg/kg daily × 3 days 4
• Alternative: Mebendazole 100 mg BID × 3 days PLUS ivermectin 200 μg/kg daily × 3 days 4
• Single-dose option: Ivermectin 200 μg/kg + albendazole 400 mg (may require repeat in 1 month) 4, 7

For confirmed Ascaris lumbricoides:

• Albendazole 400 mg single dose 4, 8
• Alternative: Mebendazole 500 mg single dose OR ivermectin 200 μg/kg single dose 8

For confirmed hookworm:

• Albendazole 400 mg single dose, repeated in 2 weeks 7

For confirmed Strongyloides stercoralis:

• Ivermectin 200 μg/kg daily × 2 days 4
• Immunocompromised patients: Ivermectin 200 μg/kg on days 1,2,15, and 16 4

Adjunctive Corticosteroid Therapy:

Prednisolone 30 mg daily for 5 days may reduce symptom duration in severe cases with significant respiratory compromise. 4, 9

Critical Management Pitfalls

CAUTION: Avoid corticosteroids if strongyloidiasis is suspected without concurrent anthelmintic coverage, as steroids can precipitate life-threatening hyperinfection syndrome. 4

Additional considerations:

• Always treat empirically for Strongyloides when using steroids in patients from endemic areas, even with negative stool studies 1, 4
• Repeat stool examination 2-3 weeks post-treatment if symptoms persist, as initial testing during prepatent period is often negative 4, 7
• Consult specialist for treatment during pregnancy, lactation, or in immunocompromised patients 4
• Most cases are self-limited, resolving within days to weeks even without treatment, but anthelmintic therapy prevents chronic infection 9, 2

Prognosis

The syndrome is benign and self-limited, typically resolving within 1 month, with excellent outcomes when appropriately treated. 9, 2, 3