The quantification of IgG anticardiolipin (aCL) antibody levels has been suggested to directly correlate with a high positive predictive value for disease progression from acute Q fever to endocarditis.35,36 Only one of our cases had quantification of IgG aCL antibody levels, which were low positive, and went on to develop persistently elevated titers without evidence of endocarditis to this date. Here, ACLY is linked to endocarditis.