A Mycophenolic Acid Concentration-Time Curve (0-12 Hours) to Maintain Remission Without Recurrent Infection in C1q...

C1q nephropathy (C1qN) presenting with steroid-resistant nephrotic syndrome (SRNS) often demands immunosuppressants to maintain remission. Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is one of the immunosuppressants used. However, MMF increases susceptibility to infection, which can lead to severe complications in some cases. Therefore, the optimal blood concentration of MMF for C1qN remains undefined. A three-year-old boy presented with SRNS due to C1qN and was treated with prednisolone (PSL) and MMF at 720 mg/day, achieving remission. However, the patient developed BK virus viruria and experienced a relapse of nephrotic syndrome (NS) simultaneously. After the MMF dose was reduced to 600 mg/day, the patient entered sustained remission without recurrent infections. Ultimately, he was able to maintain remission with only 600 mg/day of MMF, without the need for steroids. During the second remission, the area under the MPA concentration-time curve from 0 to 12 hours (MPA-AUC_0-12) was measured at 53.2 μg·h/mL, suggesting that this level may be sufficient to maintain remission while minimizing the risk of infection, and could serve as a reference point for determining the optimal blood concentration in C1qN treatment. To our knowledge, this is the first report to suggest a potentially optimal MPA-AUC_0-12 for maintaining remission in C1qN without recurrent infection. Further studies of MPA-AUC_0-12 for C1qN are warranted to confirm this result.