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Strongyloidiasis hyperinfection — ABIM Board MCQ

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HardInfectious DiseaseStrongyloidiasis hyperinfectionABIM Board

A 70-year-old man who immigrated from rural Cambodia 35 years ago and has not returned since then is hospitalized for a COPD exacerbation. He receives intravenous methylprednisolone followed by high-dose oral prednisone. Ten days later, he develops fever, abdominal pain, ileus, and hypoxemic respiratory failure. Chest imaging shows diffuse bilateral interstitial and alveolar opacities. Blood cultures obtained on separate days grow Escherichia coli and Klebsiella pneumoniae. His absolute eosinophil count, which was 900/μL several months ago, is now 0/μL. Which of the following is the most likely diagnosis?

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Correct answer: E — Strongyloides stercoralis hyperinfection syndrome

This is Strongyloides stercoralis hyperinfection syndrome. Strongyloides can persist for decades through autoinfection and then proliferate rapidly after glucocorticoid exposure. Accelerated larval migration through the gastrointestinal tract and lungs causes abdominal pain or ileus, pneumonitis, diffuse infiltrates, and respiratory failure. Migrating larvae disrupt the intestinal mucosa and transport enteric organisms, producing recurrent or polymicrobial gram-negative bacteremia. Eosinophilia may identify preceding chronic infection but is frequently absent during steroid-associated hyperinfection. Pulmonary ascariasis, acute schistosomiasis, and visceral larva migrans generally cause prominent eosinophilia and do not explain recurrent enteric bacteremia after remote exposure. Hookworm typically causes chronic gastrointestinal blood loss and iron-deficiency anemia rather than this fulminant pulmonary-gastrointestinal syndrome.

Reference: Centers for Disease Control and Prevention. Clinical Overview of Strongyloides, section 'Hyperinfection syndrome and disseminated strongyloidiasis.' Updated February 11, 2026. https://www.cdc.gov/strongyloides/hcp/clinical-overview/index.html