Löffler first described this disease in 1932, hence it is also known as Löffler syndrome. It is characterized by migratory pulmonary infiltrates with elevated peripheral blood eosinophil counts, mild pulmonary symptoms (often only a slight cough), and a self-limiting course, usually resolving spontaneously within 3 to 4 weeks.

bubble_chart Etiology

This condition is likely a transient allergic reaction of the alveoli, with common disease causes being infection by Chinese Taxillus Herb parasites and drug reactions. Approximately one-third of patients fail to identify the disease cause. The disease exhibits seasonal prevalence in certain regions, suggesting that environmental antigenic factors may also be possible disease causes in some areas.

Ascariasis is the most common disease cause, as various substances from Ascaris worms possess strong antigenicity. Experiments have shown that ingesting Ascaris eggs can lead to larval migration to the lungs, resulting in the typical pulmonary manifestations of this condition and elevated eosinophils. Other Chinese Taxillus Herb parasites that can cause this disease include hookworms, filarial worms, tapeworms, Fasciolopsis buski, Trichinella spiralis, and amoebae. Drugs implicated include para-aminosalicylic acid, aspirin, penicillin, nitrofurantoin, phenylbutazone, chlorpropamide, hydralazine, mecamylamine, sulfonamides, and methotrexate. There are also reports of this disease being triggered by inhalation of Mongolian snakegourd root or fungal spores.

bubble_chart Pathological Changes

The pathological changes are primarily located in the pulmonary interstitium, alveolar walls, and terminal bronchiolar walls, with irregular eosinophil infiltrates. Occasionally, clusters of eosinophils can be seen within the alveoli, and vascular involvement is extremely rare.

This condition may be asymptomatic and only incidentally discovered during X-ray examination. Most patients experience mild cough, small amounts of sticky sputum, and may exhibit symptoms such as lack of strength, headache, poor appetite, low-grade fever, and chest tightness, resembling a common cold. X-ray findings typically show faint, poorly defined patchy shadows distributed in unilateral or bilateral lungs, exhibiting transient migratory patterns. These shadows usually disappear within 1-2 weeks and may reappear in other areas, with most cases resolving within no more than 1 month.

Peripheral blood white blood cell counts may be normal or slightly elevated, with a significant increase in eosinophils, reaching 10-20% or 1,000-2,500/mm³. A higher number of eosinophils may also be observed in the sputum.

bubble_chart Diagnosis

The diagnosis of this condition is primarily based on the presence of elevated peripheral blood eosinophils accompanied by migratory pulmonary infiltrates, along with mild clinical symptoms and the ability to self-heal. For cases suspected to be caused by Ascaris infection, stool egg concentration tests can be performed two months after symptom onset, when the larvae have developed into adult worms in the body.

bubble_chart Treatment Measures

Generally, no treatment is needed. If drug-induced, the medication should be stopped immediately. For cases caused by Chinese Taxillus Herb insects, deworming treatment may be administered. If symptoms are significant or recurrent, adrenal cortical hormones can be used.