A 53 year old white male was admitted to the hospital for shortness of breath and cough.

An otherwise healthy individual with neurofibromatosis he had experienced the insidious onset of shortness of breath beginning two to three months prior to his admission. Accompanying the shortness of breath was a non-productive cough. He had had no fevers, chills, or sweats. His breathing difficulties progressed to the point that he had difficulty sleeping. He eventually found it easier to sleep sitting up.

He sought medical care several times prior to his eventual hospitalization. He first presented to the emergency room approximately one month prior to admission and was found to be in supraventricular tachycardia. This rhythm spontaneously converted, and he was treated with diltiazem subsequently. He was also treated at that time with a five day course of azithromycin for his cough. Later when he developed peripheral edema and orthopnea, furosemide had been substituted for the diltiazem.

The patient had no previous history of cardiac disease including rheumatic heart disease or endocarditis. He had not had recent dental work and, in fact, had not been to the dentist for several years because of lack of means. He was a local scout-
master and had no history of intravenous drug use. He had not been suffering intestinal symptoms nor arthritic symptoms. He was not around animals significantly.

At the time of the patient's hospital admission he was afebrile  but coughing, and had evidence of congestive heart failure clinically and radiographically. He had no apparent peripheral stigmata of endocarditis (splinter hemorrhages, Osler nodes, etc.) He had obvious extensive cutaneous neurofibromata (see image upper left). Laboratory data included WBC 15 (H), Hgb 12.9 (L), Plts 300; LFT's were normal. A trans-esophageal echocardiogram showed severe aortic regurgitation and a 1.8 x .8 cm hypermobile mass along the leaflets of the noncoronary cusps of the aortic valve (see image lower left).

A cardiac surgeon recommended aortic valve replacement because of the degree of valvular incompetence. Four blood cultures were obtained and the patient was begun on IV ceftriaxone for possible subacute bacterial endocarditis.

This patient had subacute bacterial endocarditis (SBE) secondary to Cardiobacterium hominis.

The patient in the preceding vignette underwent aortic valve replacement because of the severity of his aortic insufficiency. Pictured at upper left is the resected valve with the attached vegetation. Susceptibility testing is not standardized for this unusual organism. By disc diffusion it appeared sensitive to ceftriaxone which was continued as antimicrobial therapy.

Little in the preceding vignette could distinguish between the several bacterial choices offered as possible causes of SBE. Streptococcus sanguis, a viridans streptococcus, is a very common cause of endocarditis. Tropheryma whipplei, the cause of Whipple's Disease, and Coxiella burnetti, that of Q fever, remain uncommon causes of "culture negative" endocarditis in the modern era. The patient did not have other signs and symptoms of Whipple's Disease and did not seem to have epidemiologic risks for Q fever.

Infective endocarditis is thought to develop through a complex interplay of host and microbiologic factors (see schema at left). Often it is believed structurally abnormal heart valves experience fibrin-platelet deposits (nonbacterial thrombotic endocarditis) which under certain circumstances become infected by coincident bacteremias. After colonization of the valve occurs and a critical mass of adherent bacteria develops, the vegetation enlarges by further platelet-fibrin deposition and continued bacterial proliferation. The bacterial colonies are found beneath the surface of the vegetation where infiltration by phagocytic cells is minimal because of the avascular nature of valvular tissue. The use of aggressive, cidal antimicrobial therapy is thus crucial in treatment.

What role the patient's neurofibromatosis may have played in the development of his illness is unclear. No evidence of neurofibromatous involvement of his valve was evident at pathology nor does it appear that this has been described in the medical literature.

Ref: Walkty, A., Cardiobacterium hominis endocarditis: A case report and review of the literature, Can J Dis Med Microbiol, 16:5, pgs 293-297, 2005.