Background:Patients with Down syndrome have a variety of urinary tract abnormalities including obstructive hydronephrosis, dysplasia, reflux nephropathy and glomerular lesions. However, primary glomerulonephritis with prominent IgG deposits has not been reported previously in this syndrome.Case Report: A 17-year-old girl with Down syndrome presented with proteinuria and chronic renal insufficiency. A percutaneous renal biopsy revealed prominent IgG deposition without IgA or IgM deposits in the absence of an identifiable autoimmune disorder, or any other etiologic factors known to cause secondary IgG-associated glomerulonephritis.Conclusions: The glomerular lesion identified in the present case demonstrates a distinct entity that further expands the spectrum of renal disease known to occur in Down syndrome. Early detection of renal disorder in Down syndrome may prevent or slow down the progression

Keywords: Adolescent, Down Syndrome - complications, Down Syndrome - immunology, Glomerular Mesangium - metabolism, Glomerular Mesangium - pathology, Glomerular Mesangium - ultrastructure, Glomerulonephritis, Membranoproliferative - diagnosis, Glomerulonephritis, Membranoproliferative - etiology, Glomerulonephritis, Membranoproliferative - immunology, Glomerulonephritis, Membranoproliferative - pathology, Immunoglobulin G - metabolism, Adolescent, Down Syndrome - immunology, Glomerular Mesangium - ultrastructure, Glomerulonephritis, Membranoproliferative - pathology, Immunoglobulin G - metabolism