Double-seropositive anti-glomerular basement membrane (GBM) disease, characterized by the presence of both anti-GBM and anti-neutrophil cytoplasmic autoantibodies (ANCAs), is extremely rare in children. Double-seropositive patients represent a hybrid phenotype combining the severe acute kidney injury of isolated anti-GBM disease with the relapse risk and subsequent need for maintenance treatment of ANCA-associated vasculitis.

Here we present the case of an 11-year-old girl presenting with rapidly progressive glomerulonephritis leading to kidney failure and warranting kidney replacement therapy. Anti-GBM antibodies and myeloperoxidase-ANCAs were both detected in serum. Kidney histopathology revealed over 90% crescents. Despite the aggressive presentation, treatment with high-dose corticosteroids, plasmapheresis, and rituximab led to recovery of kidney function and dialysis discontinuation.

Our case suggests that rituximab, without cyclophosphamide, may represent a promising therapeutic approach in children with double-seropositive anti-GBM disease, even in severe presentations.