Infective Endocarditis with a Left Ventricular Pseudoaneurysm Caused by Proteus mirabilis: A Case Report.

Infective endocarditis (IE) due to Proteus mirabilis is rare. Given that cases of IE complicated with a left ventricular pseudoaneurysm (LVP) caused by P. mirabilis have not been reported thus far, here we report a case of IE complicated with an LVP caused by P. mirabilis. An 83-year-old woman was admitted to our hospital for urinary tract infection, and P. mirabilis was detected in blood cultures. Transesophageal echocardiography and electrocardiogram-gated computed tomography revealed mitral regurgitation and a mass protruding from the mitral annulus on the dorsal side. We made a diagnosis of an LVP due to IE and performed mitral valve replacement and patch plasty of the mitral annulus. Thus, P. mirabilis can cause bloodstream infections and lead to IE, which may result in LVPs. <Learning objective: Proteus mirabilis commonly causes urinary tract infection in older adults and is also likely to cause bloodstream infections; however, it is rarely known to be the causative agent of infective endocarditis and left ventricular pseudoaneurysms. However, in clinical settings, clinicians should be aware that P. mirabilis can also cause IE with annular extension.>.