Loefflers syndrome pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Soroush Seifirad, M.D.[2]

Overview

It is understood that Löffler syndrome is the result of transpulmonary passage of helminth larvae. Helminths, with a pulmonary life cycle are responsible for this syndrome, among them are Ascaris.lumbricoides, Ascaris. suum, Ancylostoma duodenale, Necator americanus, and Strongyloides stercoralis.

Pathophysiology

Pathogenesis

• It is understood that Löffler syndrome is the result of the transpulmonary passage of helminth larvae. Helminths, with a pulmonary life cycle are responsible for this syndrome, among them are Ascaris lumbricoides, Ascaris suum, Ancylostoma duodenale, Necator americanus, and Strongyloides stercoralis.
• Pathogen is usually transmitted via the oral route (Ascaris) or penetrate the skin (Necator) to the human host.
• Following transmission/ingestion, infecting larvae reach the lungs via the bloodstream, penetrate into alveoli, mature, and ascend the airways before descending the alimentary tract into the small bowel
• Ascaris is the most common cause of Löffler syndrome worldwide. On the other hand, migrating larvae of hookworms (Ancylostoma duodenale, Necator americanus) and Strongyloides are less likely to elicit symptoms or pulmonary eosinophilia.

Associated Conditions

Conditions associated with Loeffler syndrome include:

• Ascaris lumbricoides,
• Ascaris suum, Ancylostoma duodenale,
• Necator americanus,
• Strongyloides stercoralis.

(1) Adult worms live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces. (2) Unfertilized eggs may be ingested but are not infective. (2) and (3) Fertile eggs embryonate and become infective in 5-10 days depending on the environmental conditions (optimum: moist, warm, shaded soil). (4) Infective eggs are swallowed. (5) The larvae hatch, invade the intestinal mucosa and are carried via the portal, then systemic circulation to the lungs. (6) The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat. (7) The larvae are then swallowed. Upon reaching the small intestine, they develop into adult worms. The female Ascaris begin depositing eggs in 8-10 weeks. Adult worms can live 1 to 2 years. - Source: https://www.cdc.gov/

Gross Pathology

• Loeffler syndrome has its own characteristic imaging findings.
• Biopsy is rarely performed
• Diagnosis is based on clinical findings, radiographic findings, and shreds of evidence of parasite presence in pulmonary secretions.
• Blood-tinged sputum might be presented

Microscopic Pathology

• Eosinophils may be present in sputum
• Eosinophil-derived Charcot-Leyden crystals may be present in blood-tinged sputum
• Stool examinations are generally negative at the time of pulmonary symptoms and thus not useful in the diagnosis of Löffler syndrome.
• Ascaris, Strongyloides, or hookworm larvae might be detected in the respiratory secretions

Eosinophils in peripheral blood in a patient with eosinophilia of unknown etiology. By Ed Uthman, MD, Houston, Texas, USA - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=10813548