An Elusive Diagnosis of Strongyloides Infection Masquerading as Daptomycin-Induced Eosinophilic Pneumonitis.

Daptomycin-induced eosinophilic pneumonitis, characterized by peripheral eosinophilia, bilateral pulmonary infiltrates and respiratory symptoms, is a recognized adverse drug effect. However, these findings overlap significantly with pulmonary strongyloidiasis, in which transpulmonary larval migration provokes a similar eosinophil-rich inflammatory response. Failure to distinguish between these entities carries serious consequences, as untreated Strongyloides infection can progress to hyperinfection syndrome with high mortality. We describe a middle-aged male with alcoholic liver cirrhosis who developed peripheral eosinophilia, bilateral pulmonary nodules, migratory consolidative opacities, and pleural effusions while receiving daptomycin for polymicrobial bacteremia. The findings were initially attributed to daptomycin-induced eosinophilic pneumonitis, and the drug was discontinued. However, given clinical suspicion for a parasitic etiology, Strongyloides testing was pursued. Stool ova-and-parasite examination and bronchoalveolar lavage were both negative; however, Strongyloides serology returned positive, confirming the diagnosis. The patient improved both clinically and radiographically following treatment with ivermectin and albendazole. The negative stool and bronchoalveolar lavage results further underscore the suboptimal sensitivity of conventional diagnostic methods and the essential role of serologic testing. Clinicians evaluating eosinophilia with pulmonary infiltrates in patients receiving daptomycin should systematically consider parasitic etiologies, including Strongyloides serology, before attributing findings solely to a drug-related cause.