Infective endocarditis presenting as an isolated aneurysm of the posterior mitral leaflet.

We describe the case of a 64-year-old woman in whom an aneurysm located on the posterior mitral leaflet was detected. Blood cultures grew methicillin-sensitive Staphylococcus epidermidis, and histologic examination of the operative specimen showed polymorphonuclear neutrophilic infiltration of the valve wall associated with fibrin and necrosis, consistent with a diagnosis of endocarditis. The posterior mitral location of the aneurysm and the absence of vegetation are exceptionally rare in this setting. This case demonstrates that a mitral aneurysm may be the sole cardiac presentation of infective endocarditis.