Blood culture-negative endocarditis presenting as altered mental status

Blood culture-negative endocarditis (BCNE) is difficult to diagnose because one of the major criteria to raise suspicion for endocarditis, a positive blood culture, is absent. BCNE accounts for 2.5% to 31% of all cases of endocarditis. Our report describes a 69-year-old woman with end-stage renal disease who presented with altered mental status. Physical examination and testing, including complete blood count, comprehensive metabolic panel, chest X-ray and head CT were otherwise unremarkable. Brain MRI revealed multiple areas of decreased diffusion concerning for cardioembolic stroke. A transthoracic echocardiogram demonstrated an abnormality on the mitral valve. Operative evaluation revealed a purulent mitral valve with vegetative clumps. Cultures of the vegetation and the blood grew no organisms. BCNE is a rare entity; neurological abnormalities may be the only presenting signs/symptoms. Endocarditis should be considered among the causes of altered mental status, even in the absence of positive blood cultures.