PRTN3 and kidney disorder: Regarding treatment for PR3-ANCA-positive renal disease complicated with infectious endocarditis, previous studies suggested antibiotic monotherapy for patients with low PR3-ANCA titers (<25 IU/mL) and combination therapy with antibiotics and immunosuppressive agents for patients with high PR3-ANCA titers (>50 IU/mL) when the condition does not improve with antibiotic monotherapy.[17,18] In our patient, PR3-ANCA titer was low (11.0 IU/mL), and because of concern that immunosuppressive drugs would increase the risk of exacerbating infectious endocarditis, we initiated antibiotic monotherapy.