Loeffler Syndrome and Pulmonary Eosinophilia
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Direct answer
Loeffler syndrome is a transient eosinophilic lung infiltrate that migrates between lung zones and usually resolves within weeks, most often caused by larval migration of helminths such as Ascaris. Peripheral eosinophilia is typical and symptoms are often mild. The diagnosis rests on migratory shadows, eosinophilia and identification of a parasite or drug. Treatment is anthelmintic therapy for parasitic causes, and withdrawal of the offending drug for drug-induced cases.
What you must remember
- Origin: first described by Wilhelm Löffler, a Swiss physician, as transient pulmonary infiltrates with eosinophilia.
- Parasites: Ascaris lumbricoides is the classic cause, while Strongyloides and hookworm can produce similar migratory infiltrates.
- Drugs: nitrofurantoin, sulfonamides, penicillins and NSAIDs can cause eosinophilic lung disease, so the drug history is essential.
- Clinical picture: a mild dry cough or none, low-grade fever in some, and shadows that shift and clear within weeks.
- Investigations: peripheral eosinophilia, stool examination for ova, Strongyloides serology and serial chest films showing transient shadows.
- Treatment: albendazole or mebendazole for Ascaris, ivermectin for Strongyloides, and drug withdrawal with corticosteroids only for severe reactions.
A student with a shifting chest shadow and high eosinophils
A 19-year-old man from a rural area has mild dry cough for ten days. His chest film shows a patchy shadow in the right mid zone, and a repeat film a fortnight later shows the shadow has moved to the left lower zone. His blood count shows eosinophilia.
Loeffler syndrome should be considered when a shifting, transient infiltrate occurs with eosinophilia. The steps below separate the causes and guide treatment.
- Confirm the eosinophilia: A raised absolute eosinophil count in the blood supports an eosinophilic process rather than a bacterial pneumonia.
- Check serial films: Migratory, transient shadows that clear within weeks are typical of Loeffler syndrome rather than a fixed consolidation.
- Search for a parasite: Stool examination for ova and Strongyloides serology are sent, since helminth migration is the most common cause.
- Take a drug history: Nitrofurantoin, sulfonamides, penicillins and NSAIDs are reviewed, and the drug is stopped if it is implicated.
- Treat the cause: An anthelmintic is given for a proven parasite, and steroids are reserved for severe or persistent disease.
- Re-check the film: Repeat imaging and the eosinophil count show whether the infiltrate has resolved.
| Condition | Onset and course | Key clue |
|---|---|---|
| Loeffler syndrome | Weeks, migratory, self-limiting | Helminth or drug, shifting shadows |
| Chronic eosinophilic pneumonia | Months, persistent | Asthma, peripheral shadows, steroid-responsive |
| Acute eosinophilic pneumonia | Days, sudden and severe | Young smokers, hypoxaemia, BAL eosinophilia |
| Tropical pulmonary eosinophilia | Months, nocturnal cough | Filarial immune response, very high IgE |
The duration and the clue separate these conditions more than the chest film does. Loeffler syndrome is self-limiting, whereas chronic eosinophilic pneumonia persists and usually needs corticosteroids.
Where the exam tests the eosinophil trap
The exam tests whether you attribute every eosinophilic infiltrate to asthma or to steroids.
- Trap: assuming eosinophilia always means asthma Correct: eosinophilic lung disease has parasitic, drug and idiopathic causes, and the travel and medication history matter.
- Trap: giving steroids for every eosinophilic infiltrate Correct: treat the parasite or stop the drug first, and reserve steroids for severe or persistent disease.
- Trap: treating Loeffler syndrome with a bacterial pneumonia regimen Correct: the cause is a parasite or drug, so an anthelmintic or drug withdrawal is the right step.
- Trap: mistaking tropical pulmonary eosinophilia for Loeffler syndrome Correct: tropical pulmonary eosinophilia is a persistent filarial immune response with very high IgE, and it responds to diethylcarbamazine.
Frequently asked questions
What causes Loeffler syndrome?
Loeffler syndrome is most often caused by larval migration of helminths such as Ascaris lumbricoides. It can also be caused by drugs such as nitrofurantoin, and Strongyloides or hookworm infection can produce similar transient infiltrates during lung migration.
How is Loeffler syndrome treated?
Loeffler syndrome caused by a helminth is treated with an anthelmintic such as albendazole, and the infiltrate usually resolves within weeks. Drug-induced cases are treated by withdrawing the offending drug, with corticosteroids reserved for severe reactions.
How does tropical pulmonary eosinophilia differ from Loeffler syndrome?
Tropical pulmonary eosinophilia is a filarial immune response to microfilariae, with very high IgE and nocturnal cough. Unlike the transient, migratory Loeffler syndrome, it is persistent and responds to diethylcarbamazine.
Which investigations establish the cause of Loeffler syndrome?
Stool examination for ova and parasites, Strongyloides serology and a detailed drug history help establish the cause of Loeffler syndrome. Peripheral eosinophilia on the blood count and migratory transient shadows on serial chest films complete the picture.