Löffler's syndrome

Overview

Löffler's syndrome is a rare, transient respiratory condition characterized by the accumulation of eosinophils (a type of white blood cell) in the lungs, leading to inflammation and respiratory symptoms. It is also referred to as simple pulmonary eosinophilia. The syndrome typically presents with mild respiratory symptoms, abnormal chest imaging, and elevated eosinophil counts in the blood or lung tissue. Löffler’s syndrome is usually self-limiting and resolves on its own, especially when the underlying cause is addressed.

Causes

Löffler's syndrome is most commonly caused by a hypersensitivity reaction to parasitic infections or exposure to certain drugs or environmental allergens. Major causes include:

• Parasitic infections – especially those involving larval migration through the lungs, such as:

  • Ascaris lumbricoides (roundworm)

  • Strongyloides stercoralis

  • Ancylostoma duodenale and Necator americanus (hookworms)

• Drug reactions – certain antibiotics, NSAIDs, and other medications can trigger eosinophilic lung responses

• Allergic reactions – to inhaled environmental allergens or fungal spores

The condition results from the immune system’s overreaction, which leads to eosinophil accumulation in lung tissues and temporary inflammation.

Symptoms

Symptoms of Löffler’s syndrome are generally mild and may include:

• Dry cough

• Mild shortness of breath

• Wheezing

• Chest discomfort

• Low-grade fever

• Fatigue or malaise

In cases caused by parasitic infection, gastrointestinal symptoms such as abdominal pain or diarrhea may also be present due to the parasite’s life cycle. Most cases are asymptomatic or resolve quickly without complications.

Diagnosis

Diagnosis of Löffler’s syndrome is based on clinical history, imaging, and laboratory findings. Key diagnostic steps include:

• Complete blood count (CBC) – showing elevated eosinophil levels (eosinophilia)

• Chest X-ray – reveals transient and migratory pulmonary infiltrates, often with no corresponding symptoms

• Sputum or stool tests – to detect parasitic larvae or ova (especially Ascaris or hookworm)

• Serologic testing – may help identify parasitic infections

• Bronchoalveolar lavage (BAL) – used in unclear cases to confirm eosinophilic infiltration in the lungs

History of recent travel, medication use, or exposure to potential allergens is important for identifying the underlying cause.

Treatment

Treatment for Löffler’s syndrome depends on the underlying cause but often requires minimal intervention due to its self-limiting nature. Management may include:

• Discontinuation of offending drugs – if drug-induced

• Anti-parasitic medications – such as albendazole or ivermectin, when a parasitic infection is confirmed

• Supportive care – including rest and hydration

• Corticosteroids – rarely needed, but may be considered in severe or persistent cases to reduce inflammation

Most patients do not require hospitalization, and symptoms typically resolve within 2–4 weeks once the cause is addressed.

Prognosis

The prognosis for Löffler’s syndrome is excellent. It is typically a self-limiting condition with complete resolution of symptoms and radiological findings. Recurrence is uncommon if the underlying cause is treated or avoided. However, in rare instances where the syndrome is misdiagnosed or progresses due to repeated exposures, complications can arise. Regular follow-up is recommended to ensure resolution and rule out more serious eosinophilic lung diseases.