Abstract Introduction Strongyloides stercoralis is an intestinal nematode capable of autoinfection, allowing chronic persistence and intermittent extraintestinal involvement. Although pulmonary manifestations are well recognized in immunocompromised hosts, Strongyloides can occasionally present with fluctuating infiltrates or pleural effusion in immunocompetent individuals. Diagnosis is often delayed due to its ability to mimic more common infectious, inflammatory, or neoplastic lung diseases. Case Presentation A 31-year-old male recently returned to the U.S. after working in Middle East for six months. He presented with right-sided pleuritic chest pain, dyspnea, and night sweats for 10 days. He denied direct tuberculosis exposure but had occupational contact with healthcare workers managing TB patients. CT chest demonstrated bilateral ground-glass opacities and a moderate right-sided pleural effusion. Thoracentesis revealed an exudative effusion with a high eosinophil count (63%), while bacterial, fungal, and AFB cultures were negative. Peripheral eosinophilia had also been documented with absolute eosinophil count 1230/uL. The patient was treated empirically for community-acquired pneumonia, with partial symptomatic and radiographic improvement. At pulmonary outpatient follow-up, he continued to report persistent exertional dyspnea. Pulmonary function tests (PFTs) revealed a restrictive pattern. A subsequent CT chest showed new pulmonary nodules with resolution of prior opacities and pleural effusion, consistent with waxing and waning infiltrates. Preliminary differentials included cryptogenic organizing pneumonia, malignancy, connective tissue disease (CTD), and atypical infections including parasitic infections. Bronchoscopy with bronchoalveolar lavage (BAL) was performed. BAL was nondiagnostic and no pulmonary eosinophilia was found. CTD serologies were all negative. Strongyloides IgG was strongly positive. Ivermectin was prescribed for treatment. Discussion This case highlights the diagnostic challenge of Strongyloides infection in an immunocompetent host. Eosinophilia in both peripheral blood and pleural fluid should prompt consideration of parasitic causes. The parasite’s autoinfective life cycle can result in recurrent pulmonary inflammation, producing transient and migratory opacities that mimic organizing pneumonia, malignancy, or vasculitis. Recognition requires high clinical suspicion, particularly in patients with travel or occupational exposure to endemic regions. Conclusion Strongyloides stercoralis should be considered in the differential diagnosis of waxing and waning pulmonary infiltrates or eosinophilic pleural effusion, even in immunocompetent patients. Awareness of travel history and early serologic testing are crucial for timely diagnosis. Prompt ivermectin therapy ensures full recovery and prevents potentially fatal hyperinfection syndrome. This abstract is funded by: none
Mubasher et al. (Fri,) studied this question.