RESUMO
The diagnosis of severe mitral stenosis with left atrial thrombus was rectified at valvular replacement in a 48-year old immuno-competent man who was a cat owner. The mass in the left atrium was, in fact, a large endocarditic vegetation. Pre- and postoperative blood cultures were negative as was culture of the excised mitral valve. The diagnosis of infectious endocarditis (IE) due to Bartonella Henselae was made from a positive serological test (1600) and identification of the germ by genetic amplification. Antibiotic therapy was continued for 6 months and the patient was cured with a follow-up of 4 years. Bartonella Henselae IE is very rare (14 reported cases) and affects mainly the aortic valve, often giving rise to very large vegetations which, in half the cases, are complicated by systemic emboli. Germs like Batonella are sensitive to most antibiotics, especially the aminosides and macrolides. In Bartonella Henselae IE, valve replacement is the rule (13 out of 14 cases) and the prognosis is usually good. Sero-diagnosis of Bartonellosis should be part of the systematic investigation of all blood culture negative IE.
