Isolated Right Atrial Myocarditis Secondary to Listeria Monocytogenes

Myocarditis secondary to Listeria monocytogenes is rare but life-threatening. A 54-year-old woman with a prior history of systemic lupus erythematous on immunosuppression presented with chest pain and fever. Troponin and C-reactive protein levels were elevated, and an electrocardiogram showed T-wave inversion. Fludeoxyglucose F18 positron emission tomography showed right atrial (RA) uptake. Cardiac magnetic resonance identified RA wall thickening, akinesia, and late gadolinium enhancement, with an associated RA thrombus. Blood cultures were positive for L. monocytogenes. She received antibiotics and anticoagulation. Repeat imaging demonstrated resolution of both RA dysfunction and thrombus resolution. Myocarditis with atrial involvement is uncommon, often associated with inflammatory or autoimmune conditions. Infectious causes must be excluded before starting immunosuppressive therapy. Cardiac involvement by L. monocytogenes is unusual but may not be infrequent in immunocompromised patients. Early identification and treatment are critical. Rare causes of myocarditis should always be considered, particularly in immunocompromised patients. Multimodality imaging can help with diagnosis and guide treatment.