A case of anti-neutrophil cytoplasmic antibody-associated vasculitis with anti-glomerular basement membrane antibodies that was successfully treated with mizoribine as a safe and effective remission maintenance therapy with prednisolone and plasma exchange.

We herein report the case of myeloperoxidase (MPO) anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis with anti-glomerular basement membrane (anti-GBM) antibody positivity that successfully treated with mizoribine (MZR) as an immunosuppressive drug for remission maintenance therapy after the initiation of dialysis in addition to plasma exchange (PE) and glucocorticoid treatment to control the disease condition. A 79-year-old woman developed serious renal dysfunction and pulmonary alveolar hemorrhaging due to MPO-ANCA and anti-GBM antibody double-positive vasculitis. She was started on hemodialysis and was treated with methylprednisolone (m-PSL) pulse therapy with PE, followed by oral prednisolone (PSL). The pulmonary alveolar hemorrhaging disappeared, and both antibody titers immediately decreased but then rose again. Thus, m-PSL pulse therapy performed again in combination with combined with MZR treatment. Her poor renal function was irreversible; however, this therapy decreased both antibody titers, and they did not increase again. The patient developed pancytopenia and hyperuricemia. It was considered likely that these conditions developed in association with MZR treatment. We, therefore, measured the patient's blood concentration of MZR, and the maintenance dose was finally set at 50 mg after each dialysis session. The patient's pancytopenia and hyperuricemia improved and PSL could be smoothly tapered. This is the first case report of the use of MZR for remission maintenance therapy in a patient on hemodialysis who was positive for both ANCA and anti-GBM antibodies. The findings suggest that MZR can be used safely and effectively in such cases.