Proximal complement inhibition with pegcetacoplan in recurrent C3 glomerulopathy after pediatric kidney transplantation: a case report

C3 glomerulopathy (C3G) is a rare complement-mediated kidney disease caused by dysregulation of the alternative pathway, often leading to progressive kidney failure and high post-transplant recurrence rates. Treatment options for recurrent disease are limited, though complement inhibitors have emerged as targeted therapies. A 9-year-old girl presented with edema, hypertension, hematuria, and low C3 levels. Kidney biopsy showed dense deposit disease. Despite corticosteroids and mycophenolate mofetil, she rapidly progressed to kidney failure requiring dialysis. After kidney transplantation, early recurrence occurred within 2 months. Treatment with renin–angiotensin system blockade and the C5 inhibitor ravulizumab led to transient improvement followed by relapse. Therapy was switched to pegcetacoplan. Early improvement was noticed within 2 weeks, and normal kidney function with no hematuria or proteinuria at 6 months. This case highlights the aggressive nature of pediatric C3G after kidney transplantation and suggests that proximal complement inhibition may improve disease control and graft outcomes.