Culture-negative infective endocarditis with clinical features mimicking systemic lupus erythematosus and ANCA-associated vasculitis

Abstract

    A 75 year-old man was referred to our hospital for inflammatory disease with progressive anemia, thrombocytopenia, and renal insufficiency 9 months prior to admission. Positivity for ANCA and anti-dsDNA antibody made us suspect autoimmune diseases as the etiology, but detection of vegetation by echocardiogram led to diagnosis of infective endocarditis. Blood cultures were all negative, so we started treatment with gentamicin for 2 weeks and ceftriaxone for 6 weeks according to the protocol for culture-negative endocarditis. Decrease in CRP and size of vegetation were observed, but there was no complete recovery. Fortunately Bartonella henselae IgG and IgM antibody results turned out to be significant, led to an appropriate change in antibiotics, and finally complete remission of the inflammatory disease.　
    Patients with infective endocarditis may present rheumatic manifestations concurrent with autoantibodies. The incidence of infective endocarditis with negative culture was reported to be 2.5~31%, varying by country. Recognition of culture-negative infective endocarditis and its resemblance to autoimmune diseases is important since misdiagnosis may result in the initiation of immunosuppressive therapy, which could be detrimental to patients with infective endocarditis. Serological testing is one of the useful ways to determine the etiology of infective endocarditis.