A case of mistaken identity: subacute bacterial endocarditis associated with p-antineutrophil cytoplasmic antibody.

Seventeen cases of subacute bacterial endocarditis (SBE) associated with antineutrophil cytoplasmic antibody (ANCA) have been reported. Fifteen such cases have been associated with c-ANCA postivity and two with dual p-ANCA and c-ANCA antibodies. The authors describe a 61-year-old man with sole p-ANCA positive autoantibodies on immunofluorescence presenting with Staphylococcus aureus SBE of the aortic valve. To the best of our knowledge this is the only reported case of sole p-ANCA positive SBE. Full recovery was achieved with antibiotic treatment. ANCAs are known to be associated with infection and their characterisation in acute illness is key in differentiating a true vasculitis from an infection. Unnecessary immunosuppression can be prevented with full investigation of such patients, including both immunofluorescence and ELISA.