Pegcetacoplan-induced remission in pediatric immune-complex membranoproliferative glomerulonephritis with comorbid autosomal recessive polycystic kidney disease: a case report

Background Membranoproliferative glomerulonephritis (MPGN) is a rare glomerular disorder characterized by immune complex or complement-mediated injury, often leading to nephrotic syndrome, hypertension, and progressive renal dysfunction. Its management remains challenging, particularly in pediatric patients with coexisting renal pathologies. Case presentation We report a case of an 11-years-old girl who presented with nephrotic syndrome, severe hypertension, and impaired renal function. Renal biopsy confirmed immune complex-mediated MPGN (IC-MPGN), and genetic testing revealed a homozygous, pathogenic missense PKHD1 variant (NM_138694.3:c.4870C > T; p.(Arg1624Trp), leading to a diagnosis of autosomal recessive polycystic kidney disease (ARPKD). Initial treatment with prednisolone and mycophenolate mofetil failed to halt disease progression, and the patient became dialysis dependent. Pegcetacoplan, a complement C3 inhibitor, was subsequently initiated. After 11 weeks of pegcetacoplan therapy, the patient achieved renal recovery and was successfully weaned from dialysis. Proteinuria decreased from nephrotic to sub-nephrotic levels without significant adverse effects. Conclusion To our knowledge, this is the first pediatric case of IC-MPGN with genetically confirmed ARPKD successfully treated with pegcetacoplan. The case illustrates that renal recovery occurred following initiation of proximal complement inhibition with pegcetacoplan.