Loefflers syndrome
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Loeffler syndrome eosinophilic pulmonary
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Here is a thorough overview of Loeffler's Syndrome, drawn primarily from Fishman's Pulmonary Diseases and Disorders and supplemented by other textbooks in the library.
Loeffler's Syndrome (Simple Pulmonary Eosinophilia)
Definition
Loeffler's syndrome is a transient, self-limited form of pulmonary eosinophilia caused by the transpulmonary migration of helminth larvae. It was first described by Wilhelm Loeffler and is characterized by the triad of:
- Mild respiratory symptoms
- Peripheral blood eosinophilia
- Migratory pulmonary infiltrates on imaging
The term "simple pulmonary eosinophilia" is often used interchangeably.
Etiology and Causative Organisms
The most common cause is Ascaris lumbricoides (human roundworm). Several other parasites with lung-migratory life cycles can cause the same syndrome:
| Organism | Notes |
|---|---|
| Ascaris lumbricoides | Most common cause; human roundworm |
| Ascaris suum | Pig roundworm |
| Ancylostoma duodenale | Hookworm; common in SE USA, Mexico, C/S America |
| Necator americanus/brasiliensis | Hookworm |
| Strongyloides stercoralis | Can cause recurrent/hyperinfection |
| Trichinella spiralis | From undercooked pork |
| Toxocara canis | Dog roundworm (visceral larva migrans) |
Beyond parasites, the syndrome is also described in drug- and toxin-induced pulmonary eosinophilia and fungal infections. Loeffler syndrome occurs in up to 50% of cases of hookworm "creeping eruption."
Pathogenesis
The life cycle of Ascaris drives the pathology:
- Ingestion of Ascaris ova
- Larvae hatch in the small intestine and cross the intestinal wall
- They enter the splanchnic and pulmonary circulation
- Larvae cross pulmonary capillaries into alveoli - triggering an acute eosinophilic inflammatory response
- They ascend the airways (mucociliary escalator), descend into the alimentary tract
- Return to the small bowel to complete their life cycle
The inflammatory response is immune-mediated and is more pronounced on second and subsequent infections.
Clinical Features
- Affects all age groups
- Low-grade fever
- Nonproductive cough
- Mild to severe dyspnea
- Chest discomfort with coughing or deep breathing
- Wheezing
- Occasionally hemoptysis
- Symptoms are self-limited, resolving in 1-2 weeks
Hookworm (Ancylostoma) infections may also present with a "creeping eruption" - a raised, erythematous, serpiginous, itchy skin lesion at the site of larval skin penetration (usually the feet).
Diagnostic Studies
Blood
- Moderate to marked peripheral eosinophilia - may peak as respiratory symptoms resolve
- Eosinophilia itself may persist for weeks even as symptoms clear
Sputum
- Eosinophils present in expectorated sputum
- Charcot-Leyden crystals (crystallized eosinophil proteins) may be found
Imaging (CXR / CT)
- Transient/migratory, nonsegmental, bilateral infiltrates
- Often peripheral or pleural-based
- Interstitial and alveolar pattern
- Infiltrates clear over several weeks - the "fleeting" or migratory nature is a hallmark
Pulmonary Function Tests
- Mild-to-moderate restrictive ventilatory defect
- Reduced DLCO (diffusing capacity for CO)
Microbiological / Parasitological
- Larvae can be recovered from sputum, BAL, or gastric aspirate during the pneumonic phase
- Stool O&P (ova and parasites) is negative for the first ~8 weeks after onset of respiratory symptoms (because larvae haven't yet completed their life cycle and returned to the intestine)
- Clinical follow-up for 2-3 months is therefore indicated
Histology (if obtained)
- Striking eosinophilic infiltration of interstitial and alveolar-capillary units
- Increased macrophages
- No tissue necrosis or vasculitis
- Larvae may occasionally be seen in tissue
Treatment
| Component | Details |
|---|---|
| Symptomatic | Bronchodilators for wheezing; corticosteroids rarely needed |
| Antiparasitic | Mebendazole 100 mg twice daily x 3 days (or 500 mg single dose) - to prevent late GI complications |
| Alternatives | Pyrantel pamoate, albendazole, or ivermectin |
| Follow-up | 2-3 months, as early stool O&P will be negative |
Why treat if self-limited? - Because the Ascaris larvae will eventually reach the intestine and mature into adult worms, leading to late GI complications including malnutrition, diarrhea, abdominal pain, and intestinal obstruction (appearing ~8 weeks or more after respiratory onset).
Classification Context: Pulmonary Eosinophilic Syndromes
Loeffler syndrome falls under the broader group of pulmonary eosinophilic syndromes of known cause, which includes:
- Parasitic-induced eosinophilic pneumonias (including Loeffler syndrome)
- Drug- or toxin-induced eosinophilic pneumonias
- Tropical pulmonary eosinophilia (associated with Wuchereria bancrofti, Brugia malayi - presents with paroxysmal cough, bronchospasm, marked eosinophilia in tropical regions)
- Allergic bronchopulmonary mycosis (e.g., ABPA)
Key distinction from Loeffler's endocarditis:
Loeffler's endocarditis (also called eosinophilic endomyocardial disease) is a separate condition - a restrictive cardiomyopathy caused by sustained hypereosinophilia (as in idiopathic hypereosinophilic syndrome). It shares the eponym but is clinically and pathologically distinct from pulmonary Loeffler's syndrome.
Summary Table
| Feature | Detail |
|---|---|
| Cause | Helminth larval migration (most commonly Ascaris) |
| Mechanism | Immune-mediated eosinophilic lung inflammation during transpulmonary larval passage |
| Symptoms | Cough, wheeze, low-grade fever, dyspnea - self-limited (1-2 weeks) |
| Eosinophilia | Peripheral blood - moderate to marked |
| Sputum | Eosinophils + Charcot-Leyden crystals |
| CXR | Migratory, fleeting, bilateral, peripheral infiltrates |
| Stool O&P | Negative in first 8 weeks |
| Treatment | Mebendazole (or albendazole/ivermectin); bronchodilators if needed |
| Prognosis | Excellent - self-limited |
Source: Fishman's Pulmonary Diseases and Disorders, 2-Volume Set; Murray & Nadel's Textbook of Respiratory Medicine; Harrison's Principles of Internal Medicine 22E
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