An unexpected case of Coxiella burnetii endocarditis

Introduction. Coxiella burnetii is the causative agent of Q fever, a zoonosis that is usually associated with cattle, sheep, goats and their bodily fluids, mainly milk or amniotic fluid. The disease manifests most commonly as an upper respiratory tract infection or pneumonia, but, in less common cases can lead to endocarditis, hepatitis, meningo-encephalitis and osteomyelitis. In the acute stage, patients usually have a self-limited febrile illness, which can progress to the chronic form of Q fever, most commonly with endocarditis. Endocarditis is the main manifestation of chronic Q fever and it usually affects patients with risk factors, such as prosthetic valves, abnormal native valves or other cardiac disease history, but it can also be seen in patients with no prior medical history, like the one we describe. The diagnosis is confirmed using the same Duke Criteria used in infectious endocarditis, with one major criterion being either a positive blood culture or PCR for C. burnetii, or a positive IgG phase I serological test [>1:6400). The preferred treatment regimen is doxycycline plus hydroxychloroquine, maintained for a minimum of 18 months, along with regular follow-ups for serology testing and side-effects evaluation. Case presentation. We describe the case of a 53-year old male with no medical history who presented in our clinic for a 2-week evolution of fever, chills and weight loss. The physical examination revealed no pathological findings. The trans-esophageal cardiac echography showed small vegetations on the mitral valve and the serological test for Coxiella burnetii was positive, thus allowing us to confirm the diagnosis of Coxiella burnetii endocarditis and start treatment with Doxycycline and Hydroxychloroquine. Conclusions. Coxiella burnetii must be taken into account as a possible diagnosis for culture-negative endocarditis, even in patients with no cardiological medical history and no environmental risk factors.