Löffler’s Syndrome (Simple Pulmonary Eosinophilia)

Overview

Löffler’s syndrome, also known as simple pulmonary eosinophilia, is a transient, eosinophil‑rich inflammatory disease of the lungs. It is characterized by brief episodes of coughing, wheezing and, most notably, an increase in eosinophils (a type of white blood cell) within the lungs and peripheral blood. The condition is usually self‑limited, lasting from a few weeks to a few months, and most people recover without permanent lung damage.

The syndrome was first described by the Austrian physician Wilhelm Löffler in 1932, after observing a group of patients with migrating lung infiltrates and marked eosinophilia. Today, it is recognized as a hypersensitivity reaction to parasites (most commonly helminths) or, less frequently, to certain medications and environmental allergens.

Who it affects: The disease can affect anyone, but it is most common in children and young adults who live in rural or tropical areas where soil‑transmitted helminths are endemic. In non‑endemic regions, infection is often linked to travel.

Prevalence: Exact global incidence is unclear because many cases are mild and go undiagnosed. In the United States, eosinophilic lung diseases collectively account for < 0.5 % of all respiratory diagnoses, and Löffler’s syndrome makes up a small fraction of those cases. In endemic areas of sub‑Saharan Africa and Southeast Asia, seroprevalence of the most common causative parasite (Ascaris lumbricoides) can exceed 30 %, and isolated reports suggest Löffler’s syndrome occurs in up to 5 % of infected individuals.^CDC

Symptoms

Symptoms develop 1–4 weeks after exposure to the offending parasite or allergen and often follow a characteristic pattern:

• Cough: Dry or minimally productive; may be persistent.
• Wheezing or shortness of breath: Especially on exertion; can mimic asthma.
• Fever: Low‑grade (37.5–38.5 °C) in about 40 % of cases.
• Chest tightness or pleuritic pain: Usually mild.
• Fatigue and malaise: Common but nonspecific.
• Peripheral eosinophilia: Blood eosinophil count > 500 cells/µL; often > 1,500 cells/µL.
• Transient pulmonary infiltrates: Detected on chest X‑ray or CT; usually peripheral and migratory.
• Gastrointestinal symptoms: Nausea, abdominal discomfort, or diarrhea may accompany helminth infection.

Most patients experience the full constellation within a few weeks, and symptoms typically resolve spontaneously within 2–8 weeks.

Causes and Risk Factors

Parasitic infections – the most common cause

• Ascaris lumbricoides (large roundworm) – ingestion of embryonated eggs from contaminated soil or food.
• Hookworms (Ancylostoma duodenale, Necator americanus) – larvae penetrate skin, often through bare feet.
• Strongyloides stercoralis – can cause chronic infection and eosinophilic pulmonary migration.
• Trichinella spiralis – from undercooked pork or wild game.

Non‑parasitic triggers

• Medications: certain antibiotics (e.g., penicillins), anti‑epileptics, and non‑steroidal anti‑inflammatory drugs (NSAIDs).
• Inhaled allergens: mold spores, dust mites, and some occupational exposures (e.g., farmer’s lung).
• Idiopathic: a small percentage have no identifiable cause.

Risk factors

• Living in or traveling to areas with poor sanitation where soil‑transmitted helminths are common.
• Childhood exposure – children are more likely to ingest contaminated soil.
• Occupations with frequent soil contact (agriculture, construction, mining).
• Immunocompromised states can increase parasite burden, although severe disease is more typical of hyperinfection syndromes rather than classic Löffler’s.

Diagnosis

Diagnosis rests on a combination of clinical history, laboratory findings, and imaging. The classic triad includes:

1. Peripheral eosinophilia.
2. Transient, migratory pulmonary infiltrates on imaging.
3. Evidence of a recent parasitic infection or exposure.

History and Physical Examination

• Recent travel to endemic regions, consumption of raw/undercooked meat, or exposure to contaminated soil.
• Medication review to rule out drug‑induced eosinophilia.
• Physical exam may reveal wheezes, crackles, or a normal chest exam.

Laboratory Tests

• Complete blood count (CBC): Elevated eosinophil count; > 1,500 cells/µL in most cases.
• Serology: Antibody tests for Ascaris, Strongyloides, Hookworm, etc., help identify the parasite.
• Stool ova and parasite exam: Three separate specimens increase detection rates up to 70 %.
• Serum IgE: Often elevated, supporting an allergic/hypersensitivity reaction.

Imaging

• Chest X‑ray: Peripheral, ill‑defined infiltrates that may shift locations over days to weeks.
• High‑resolution CT (HRCT): Shows ground‑glass opacities, nodular lesions, or pleural-based infiltrates; useful to rule out other eosinophilic lung diseases.

Additional Tests (when diagnosis is unclear)

• Bronchoalveolar lavage (BAL): Demonstrates eosinophils > 25 % in the recovered fluid.
• Lung biopsy: Rarely needed; would show eosinophilic infiltrates without vasculitis.

Treatment Options

Because Löffler’s syndrome is usually self‑limited, the main therapeutic goals are to eradicate the underlying cause, relieve symptoms, and prevent complications.

Antiparasitic Medications

• Albendazole 400 mg orally twice daily for 3 days (effective for Ascaris, hookworms, and most soil‑transmitted helminths).^{Mayo Clinic}
• Mebendazole 100 mg twice daily for 3 days – an alternative where albendazole is unavailable.
• Ivermectin 200 µg/kg single dose – preferred for Strongyloides stercoralis.
• For Trichinella, albendazole** plus** a short course of corticosteroids may be needed if muscle involvement is severe.