Double Renal Pathology with Favorable Response to Pegcetacoplan in a Pediatric Patient: A Case Report

Introduction: MPGN is a rare histological pattern of immune-mediated kidney injury. It has recently been reclassified into two major subtypes: IC-MPGN and C3G. ARPKD is a chronic inherited disorder characterized by cystic kidney changes and a gradual decline in renal function. Case Description: An 11-year-old girl who initially presented with nephrotic-range proteinuria, edema, hypertension, bicytopenia, and hepatosplenomegaly. Despite initial immunosuppressive therapy with steroids and MMF, her condition deteriorated. A biopsy confirmed IC-MPGN, and she developed progressive renal dysfunction requiring dialysis. Endoscopy revealed esophageal varices, and genetic confirmed ARPKD. In light of her refractory disease course, off-label treatment with pegcetacoplanwas initiated. Following the initiation of pegcetacoplan, she experienced clinical and biochemical improvement. Her urine output progressively increased, creatinine decreased from 450 µmol/L to 129 µmol/L, and proteinuria declined from 6 g/day to 0.9 g/day. Dialysis was discontinued after 11 weeks. Discussion: This case highlights a rare overlap of ARPKD and IC-MPGN, and demonstrates a favorable clinical response to pegcetacoplan following failure of conventional therapies. It supports a potential “double-hit” hypothesis and emerging role of complement inhibition in managing severe, treatment-resistant glomerular disease.