Related Subjects: Asthma
|Acute Severe Asthma
|Eosinophilic granulomatosis (Churg Strauss)
|Loffler's syndrome (Pulmonary Eosinophilia)
|Pulmonary Eosinophilia and CXR changes
|Drug Reaction Eosinophilia Systemic Symptoms
Löffler’s Syndrome (Simple Pulmonary Eosinophilia) – Updated Feb 2026
🌍 Löffler’s Syndrome (also called simple pulmonary eosinophilia) was first described by Wilhelm Löffler in 1932. It is a self-limited hypersensitivity reaction of the lungs characterised by transient peripheral eosinophilia + fleeting migratory pulmonary infiltrates on imaging.
It is most often triggered by migrating parasites (especially Ascaris) or drugs, but can be idiopathic. Symptoms are usually mild or absent, and the condition resolves spontaneously within 2–4 weeks once the trigger is removed. Recognition prevents unnecessary investigations or repeated exposures.
🧬 Aetiology & Pathophysiology
- Core mechanism: Inhaled or ingested antigen (parasite larvae, drug) → type I hypersensitivity → massive eosinophil recruitment into lung parenchyma and alveoli.
- Eosinophils degranulate, releasing major basic protein, eosinophil cationic protein, and leukotrienes → localised inflammation, alveolar damage, and transient infiltrates.
- No permanent lung damage in classic Löffler’s (unlike chronic eosinophilic pneumonia or EGPA).
- Peripheral eosinophilia: often 1,000–10,000/μL (can exceed 20,000/μL in heavy parasite load).
🪱 Causes (High-Yield Triggers)
| Category | Common Agents | Notes |
|---|
| Parasitic (most common worldwide) | Ascaris lumbricoides (larval migration phase), hookworm, Strongyloides, Toxocara, Trichinella, Fasciola, Schistosoma | Ascaris is the classic cause. Larvae migrate through lungs 4–14 days after ingestion → peak symptoms. |
| Drug-induced | Nitrofurantoin, sulfonamides, aspirin/NSAIDs, penicillin, amiodarone, hydralazine, methotrexate, imipramine | Nitrofurantoin is the highest-yield drug in exams. Onset days to weeks after starting. |
| Other / Idiopathic | Allergens (pollens, moulds), tropical pulmonary eosinophilia (filaria), idiopathic acute eosinophilic pneumonia | Rarely autoimmune overlap. |
🩺 Clinical Features
- Most common presentation: Asymptomatic or mild — incidental finding on CXR in a traveller or patient on nitrofurantoin.
- Symptoms (usually mild and transient):
- Low-grade fever (38–39°C).
- Dry cough or mild wheeze.
- Chest discomfort, fatigue, malaise.
- Rarely: haemoptysis, dyspnoea, night sweats.
- Timeline: Symptoms peak 4–14 days after parasite ingestion or drug exposure; resolve spontaneously within 2–4 weeks once trigger removed.
- Recurrence: Common if re-exposed (e.g., repeated nitrofurantoin courses or endemic travel).
🔬 Investigations (Step-wise Approach)
- Basic bloods: FBC — peripheral eosinophilia (>500/μL, often 10–30% of WBCs).
- Imaging:
- CXR: classic “fleeting” peripheral, non-segmental infiltrates (often upper lobe, “photographic negative of pulmonary oedema”). Infiltrates migrate or resolve within days to weeks.
- CT chest (if needed): peripheral ground-glass opacities, consolidation without cavitation.
- Stool & sputum: Microscopy for ova/parasites (Ascaris larvae may be seen in sputum during migration phase).
- Serology: Parasite-specific IgE or antibody tests if travel history (Toxocara, Strongyloides, filaria).
- Additional if severe: Bronchoalveolar lavage (BAL) — >25% eosinophils; lung biopsy rarely needed.
💊 Management (Step-by-Step)
- Identify & remove trigger (most important step):
- Stop offending drug immediately.
- Treat helminth infection: albendazole 400 mg single dose (Ascaris/hookworm) or ivermectin 200 μg/kg (Strongyloides).
- Supportive care: Most cases self-limiting — no specific therapy needed.
- Steroids: Use only in severe/prolonged cases or idiopathic eosinophilic pneumonia:
- Prednisolone 0.5–1 mg/kg/day for 7–14 days, then taper.
- Monitoring: Repeat CXR in 2–4 weeks; repeat FBC until eosinophilia resolves.
📌 Differentials (High-Yield Comparison Table)
| Condition | Eosinophilia | Infiltrates | Duration | Systemic Features | Key Distinguisher |
|---|
| Löffler’s Syndrome | Mild–moderate | Fleeting, peripheral | Days–weeks | Mild cough/fever | Self-limiting, parasite/drug trigger |
| Chronic Eosinophilic Pneumonia (CEP) | Marked | Peripheral “photographic negative” (chronic) | Weeks–months | Weight loss, night sweats | Responds dramatically to steroids |
| EGPA (Churg–Strauss) | Very high | Patchy, migratory | Chronic | Asthma, vasculitis, neuropathy, ANCA+ | Multi-organ involvement |
| Tropical Pulmonary Eosinophilia | Extreme (>3,000/μL) | Diffuse reticulonodular | Chronic if untreated | Paroxysmal nocturnal cough | Filarial (Wuchereria, Brugia); high IgE |
| Acute Eosinophilic Pneumonia | Moderate | Diffuse alveolar | Acute (days) | Rapid respiratory failure | No peripheral eosinophilia initially; BAL >25% eosinophils |
📌 Key Exam Pearls (OSCE & Viva)
- 🪱 Think parasites first in any patient with travel history + eosinophilia + fleeting CXR infiltrates.
- 💊 Nitrofurantoin and sulfonamides are the highest-yield drug triggers in UK exams.
- Always ask: recent travel, new medications, occupational exposures (e.g., farmers — Ascaris).
- Distinguish from EGPA (systemic vasculitis + asthma + neuropathy) and chronic eosinophilic pneumonia (chronic course, dramatic steroid response).
- CXR hallmark: peripheral, migratory (“photographic negative of pulmonary oedema”).
Teaching Point 🩺
Löffler’s = transient, self-limiting pulmonary eosinophilia triggered by parasites (Ascaris most common) or drugs.
Classic triad: mild symptoms + peripheral eosinophilia + fleeting CXR infiltrates that resolve in 2–4 weeks.
Management: remove trigger + supportive care; steroids only if severe.
Always consider differentials (EGPA, CEP, tropical pulmonary eosinophilia) and investigate travel/drug history.
📚 References (Feb 2026)
- Radiopaedia: Löffler Syndrome (updated 2025).
- Fishman’s Pulmonary Diseases and Disorders (6th ed., 2025).
- UpToDate: Eosinophilic Lung Diseases (2026).
- Recent review: Parasitic Eosinophilic Lung Disease. Lancet Respir Med 2025.
