This report details two unprecedented cases of Legionnaires' disease caused by Legionella cardiaca. The first patient, a 70-year-old male with a history of lymphoma, presented with fever, cough, and dyspnea, developing severe pneumonia. The second, a 69-year-old male with multiple comorbidities, also presented with respiratory distress and pneumonia. Both were diagnosed via next-generation sequencing and culture, confirming L. cardiaca as the causative agent. This bacterium was previously only known from a single endocarditis case. These cases highlight its potential to cause severe respiratory infections in immunocompromised individuals.
Key note: Legionella cardiaca can cause severe pneumonia, expanding its known clinical spectrum beyond endocarditis.