A Twist in the Tale: An Unexpected Pathogen in a Patient With a Cavitary Lung Lesion

We present a challenging case of <i>Legionella pneumophila </i>lung abscess in a 58-year-old woman with myelodysplastic syndrome presenting with a cavitary lung lesion. The diagnostic workup was complicated by a false-positive galactomannan result, resulting in unnecessary medicamentous treatment and possible different therapeutic decisions. Management involved surgical resection regarding a necessary stem cell transplant and prolonged antibiotic (with monotherapy versus broad-spectrum) and antifungal therapy. This case highlights the need to consider atypical pathogens in immunocompromised patients, even when other findings suggest more common infections, and underscores the importance of a multidisciplinary approach and careful interpretation of laboratory results to guide appropriate management strategies.