Legionella Myocarditis with Reversible Left Ventricular Dysfunction in a Patient Receiving Adalimumab: A Case Report

Legionella pneumophila is a well-recognized cause of community-acquired pneumonia, but its capacity to cause extrapulmonary complications, including myocarditis, remains underappreciated. Myocarditis is among the rarest and most serious cardiac manifestations of Legionella infection and may be underdiagnosed in critically ill patients, where troponin elevations are often attributed to sepsis-related myocardial injury. We report the case of a 51-year-old woman with diabetes mellitus, ulcerative colitis managed with adalimumab (a tumor necrosis factor-α inhibitor), and a significant smoking history who presented to the emergency department after being found unresponsive. She was febrile, tachycardic, and in respiratory distress, with laboratory findings significant for markedly elevated troponin (7,377 ng/L), creatine kinase (10,561 U/L), and procalcitonin (27 ng/mL). Echocardiography revealed severe left ventricular systolic dysfunction with an ejection fraction of less than 15%. A urine antigen test confirmed Legionella pneumonia. Hemodynamic assessment using the Fick method excluded cardiogenic shock, and left heart catheterization demonstrated no obstructive coronary artery disease. Following a 14-day course of levofloxacin along with supportive care, her cardiac function recovered completely, with a follow-up ejection fraction of 71%. This case highlights the potential for Legionella infection to cause fulminant yet fully reversible myocarditis and underscores the role of TNF-α inhibitor therapy as a predisposing factor for severe Legionella disease. Clinicians should maintain a high index of suspicion for myocarditis in patients with Legionella pneumonia who present with unexplained troponin elevation and new systolic dysfunction, as early recognition and targeted antimicrobial therapy can lead to complete cardiac recovery.