Quiescent Q fever endocarditis exacerbated by cardiac surgery and corticosteroid therapy.

Q fever endocarditis occurs in up to 11% of patients infected by Coxiella burnetti. Major clues for the diagnosis are culture-negative endocarditis, hepatic involvement, rash, and thrombocytopenia. Characteristically, the diagnosis is delayed. In our patient, Q fever endocarditis occurred without previously recorded signs of infection. Fever, rash, and hepatic involvement all occurred following aortic valve replacement. The histologic picture of the excised valve was consistent with endocarditis, and serologic tests disclosed elevated IgA and IgG antiphase 1 antibody titers against C burnetti, compatible with Q fever endocarditis. It is assumed that the exacerbation of quiescent Q fever endocarditis was caused by cardiac surgery and steroid therapy.