Immunotactoid glomerulopathy in a child with Down syndrome.

A 9-year-old girl with Down (21-trisomy) syndrome was found to have proteinuria and microscopic haematuria at age 6 years. Proteinuria gradually increased during the next 3 years, although blood pressure and renal function remained normal. The patient exhibited no underlying systemic diseases, monoclonal gammopathy, cryoglobulinaemia or histological evidence of plasmacytoma. A percutaneous renal biopsy revealed immunotactoid glomerulopathy (fibrillary glomerulonephritis) characterized by thickening of the glomerular basement membrane, diffuse mesangial expansion and various-sized acid-Schiff-positive nodules that were intensely positive for IgG, light chains (kappa and lambda) and complement components (C3, C4, C1q) along the glomerular capillaries in the mesangium. Congo red dye and amyloid thioflavine T staining were negative. Fibrils (15-17 nm in diameter--larger than amyloid fibrils) were present in the mesangial area and within the glomerular basement membrane. We are not aware of a previous report of immunotactoid glomerulopathy and a patient with chromosomal abnormalities.