Q fever endocarditis: A case report and review of the literature

Abstract

E ndocarditis is the most common presentation of chronic Q fever, a zoonosis caused by the obligate intracellular bacteria Coxiella burnetii. Commonly believed to be a rare disorder, it has been estimated to account for up to 5% of all endocarditis cases worldwide (1-3). It occurs almost exclusively in patients who have pre-existing valvular disease or who are immunocompromised (4). Unlike typical cases of endocarditis, the clinical presentation of chronic Q fever is often nonspecific. Furthermore, specialized techniques are required for identification of the organism, and echocardiographic evidence of infection is frequently absent (5). Without prompt recognition and appropriate antimicrobial therapy, the course of Q fever endocarditis is severe and potentially fatal. The following case demonstrates many of the clinical features of chronic Q fever and highlights the difficulty of obtaining the diagnosis. CASE PRESENTATIONA 31-year-old Caucasian man presented to a walk-in clinic complaining of progressive, exertional shortness of breath. He had moved to Calgary, Alberta, from Nova Scotia, where he had worked on a dairy farm, two years prior. Due to pre-existing congenital valvular heart disease, he was referred to the Adult Congenital Cardiology Clinic at the University of Calgary (Calgary, Alberta). The patient could barely climb one flight of stairs without significant shortness of breath, and had developed orthopnea and paroxysmal nocturnal dyspnea. He described occasional palpitations, but denied any syncopal episodes, chest discomfort or peripheral edema. There were no symptoms suggestive of systemic infection.Of note, the patient had been diagnosed with congenital aortic stenosis at the age of eight months and underwent open aortic valvulotomy. The patient was found to have a trileaflet valve with significant fusion of the leaflets. Catheterization at the age of 10 years revealed a peak residual gradient of 25 mmHg across the aortic valve with mild aortic insufficiency. Echocardiograms at the ages of 18 and 22 years demonstrated peak gradients of 37 mmHg and 56 mmHg, respectively, moderate aortic insufficiency and preserved left ventricular function. The patient had no cardiology follow-up after the age of 22 years.Physical examination revealed a blood pressure of 110/50 mmHg, a heart rate of 82 beats/min and a normal The case of a 31-year-old man from Alberta diagnosed with Q fever endocarditis is presented. To the authors' knowledge, this is the first case of Q fever endocarditis diagnosed in the province of Alberta. The patient had undergone open valvulotomy for congenital aortic stenosis as an infant. He presented with congestive heart failure secondary to severe aortic regurgitation and underwent mechanical aortic valve replacement. Early failure of the mechanical prosthesis and numerous laboratory abnormalities prompted an investigation for endocarditis, which was initially negative. Markedly positive serology eventually established the diagnosis of chronic Q fever. The patient subsequently underwent...

Severe acute Q fever pneumonia complicated by presumed persistent localized Q fever endocarditis in a renal transplant recipient: A case report and review of the literature

“…Her titers were slow to decrease, but this may be expected within the first 3‐6 months after the acute illness. However, since she did develop mild aortic valve thickening, there was concern for development of endocarditis, since echocardiographic evidence of infection may be absent in Q fever endocarditis . One study showed that TTE revealed abnormalities in only 12% of cases, which is due to the small size and nodular shape of the vegetations .…”

“…Additionally, the Duke criteria for infective endocarditis were revised in 2000 to include a Q fever phase I IgG titer of greater than 1:800 or a single positive blood culture for C burnetti as a major criterion . A phase I IgG titer of greater than 1:800 has been shown to have a specificity of 99.6% for diagnosis of Q fever endocarditis . Our patient's TEE remained inconclusive, and given the high mortality of approximately 37% associated with Q fever endocarditis due to delays in diagnosis and treatment, the benefits of empiric treatment were thought to outweigh the risks .…”

“…However, since she did develop mild aortic valve thickening, there was concern for development of endocarditis, since echocardiographic evidence of infection may be absent in Q fever endocarditis. 14 One study showed that TTE revealed abnormalities in only 12% of cases, which is due to the small size and nodular shape of the vegetations. 6,15 Another study showed that TEE identified valvular lesions in only 5 out of 15 patients with Q fever endocarditis.…”

Q Fever Endocarditis in a Patient With Bioprosthetic Heart Valves

“…In Q fever endocarditis, blood cultures are usually negative, and transthoracic echocardiogram is not sensitive for demonstrating vegetations. 4 Serology is key to diagnosis, as there is no available routine culture. Usually, an increase in phase 1 IgG antibodies to 1:800 or greater is confirmatory for diagnosis of chronic Q fever endocarditis with a sensitivity of 100% and specificity of 99.6%, although an increase phase 1 IgG antibodies to 1:128 or greater is also supportive.…”

“…Increase in phase II IgG antibodies to 1:200 or greater has sensitivity of 81.9% and specificity of 96.1% and phase II IgM to 50 or greater has sensitivity of 67.2% and specificity of 98.8% for diagnosis of active Q fever. 1,2,4,5 Doxycycline and hydroxychloroquine combination has been shown to be effective therapy for Q fever endocarditis. Despite delay in diagnosis and treatment, the patient has done well since the initiation of appropriate therapy.…”