ABSTRACT
Q fever is a zoonotic infection caused by Coxiella burnetii. The most common clinical manifestation of acute Q fever infection is as an atypical community-acquired pneumonia. The pulmonary findings are accompanied by extrapulmonary findings, most typically an increase in serum transaminases and splenomegaly. Because C. burnetii is difficult to culture, the diagnosis of Q fever is usually made serologically. The diagnosis of acute Q fever atypical community-acquired pneumonia is made by demonstrating a fourfold or greater increase in titer between acute and convalescent specimens or by demonstrating elevated immunoglobulin (IgM) (phase II) titers. Chronic Q fever is manifested as granulomatous hepatitis or more commonly as culture-negative endocarditis (CNE). Chronic Q fever (CNE) is a difficult diagnosis because of difficulty in culturing the organism from the blood and the vegetations with Q fever CNE are small or absent. The diagnosis of chronic Q fever CNE is based on serology. Such patients commonly have highly elevated IgM and IgG titers (phase I/II) titers. Chronic Q fever CNE may involve native or prosthetic heart valves. Q fever prosthetic valve endocarditis is rare compared with native valve Q fever endocarditis. Q fever prosthetic valve endocarditis usually requires valve replacement for cure. We present a case of chronic Q fever bioprosthetic aortic valve endocarditis that was successfully treated with doxycycline monotherapy that did not require aortic valve replacement.