Legionella maceachernii Pneumonia Presenting as a Cavitary Lesion in an Immunocompromised Patient.

is an intracellular, gram-negative bacterium known as a less common cause of pneumonia, which has become a public health concern in recent years due to increased incidence. is recognized as the most common cause of Legionnaires' disease. Other species, including , have been rarely described as causes of Legionnaires' disease. Moreover, cavitary lesions as radiological findings in patients with Legionnaires' disease are uncommon but have been reported, especially in immunocompromised patients. Although the gold standard for diagnosis is a positive culture, the need for special media and extended time for growth can overlook or delay diagnosis. Additionally, urine antigen testing will miss detection of species other than serogroup 1. Molecular testing, although not routinely performed, is a promising tool for early detection and identification of other species. We present a case of an immunocompromised patient presenting with fevers and a cavitary lesion, diagnosed with through cell-free DNA sequencing.