Mitral valve annular bacterial vegetative mass masquerading as a left atrial myxoma

A 49-year-old male with chronic kidney disease and history of renal transplantation in 2006 on chronic immunosuppressant therapy presented with a 1-week history of chills and generalized myalgia. He had a temperature of 101 degrees F. One set of blood cultures grew methicillin-sensitive Staphylococcus aureus. Transesophageal echo (TEE) revealed a mobile mass that was 2 cm in length attached by a thin stalk to the base of the anterior leaflet of the mitral valve. The surgical diagnosis was a left atrial myxoma. The echocardiographic as well as the surgical findings were consistent with an atrial myxoma. However, the histopathology of the specimen showed no evidence of myxoma as the characteristic stellate mesenchymal cells were absent. Instead the milieu of inflammatory cells, fibrin and multimicrobial colonization of both Gram-positive and Gram-negative cocci suggested a super infected vegetative mass. It is interesting that the mitral valve was intact as de novo vegetation being formed on a structurally normal native valve is rare. In some instances, the echocardiographic distinction between atrial masses such as vegetation, thrombus or an atrial myxoma may be ambiguous. Not only does surgical removal allow histological determination of the diagnosis that is critical for treatment, but in cases where an infected mass is mobile and greater than 15 mm, as in this case, there is high potential for embolization. Surgical removal significantly decreases the risk of an embolic event.