Two Cases of Recurrence Immediately after Living Donor Kidney Transplantation for ANCA-Associated Vasculitis (AAV)

Introduction: Rituximab, the standard treatment for AAV, reduces B cells and suppresses antibody production, thus contributing to the prevention of AAV recurrence. The two cases presented here are precious cases of recurrent AAV immediately after kidney transplantation (KT). Case Description: [Case 1] A 24-year-old woman diagnosed with AAV 7 years ago, was treated with steroid pulse therapy, plasma exchange, and rituximab, but her renal function declined, and she was introduced to hemodialysis four years ago. MPO-ANCA remained positive, and a blood group-mismatched living donor KT was performed with her aunt as donor. On postoperative day 8, serum creatinine worsened to 2.16 mg/dL and kidney biopsy revealed tuft necrosis. She was considered to have recurrent AAV and creatinine improved to 1.57 mg/dL with steroid pulse and plasma exchange. Repeat biopsy after KT showed still tuft necrosis and fibrocellular crescents. After administration of avacopan, creatinine remained at 1.5-1.7 mg/dl. [Case 2] A 23-year-old woman diagnosed with AAV 18 months ago, was treated with steroid pulse therapy and rituximab, but kidney biopsy showed devastated glomeruli and fibrous crescents, and hemodialysis was introduced. MPO-ANCA remained positive, and a blood group-matched living donor KT was performed with her mother as donor. On postoperative day 4, creatinine deteriorated to 3.34 mg/dL and biopsy showed focal fibrinoid necrosis and cellular crescents. She was diagnosed to have recurrent AAV and was treated with steroid pulse, plasma exchange, cyclophosphamide pulse, and abacopan. Proteinuria and hematuria resolved, and creatinine improved to 1.49 mg /dL. Discussion: The recurrence rate of AAV after KT is reported to be about 10%, and even if recurrence occurs, treatment is successful with intensified immunosuppressive therapy, making KT highly beneficial. ANCA antibody titer before KT does not affect the recurrence rate, so KT should not be postponed because of ANCA positivity. However, KT within one year of remission is associated with increased mortality. Among cases presenting with RPGN, relapse is reported to be more common in ANCA-positive cases than in non-positive cases. The fact that AAV recurred immediately after administration of rituximab, also used in KT, suggests that the MPO-ANCA-producing cells may have already changed from B cells to plasma cells.