Acute renal failure in a neonate caused by the transplacental transfer of a nephrotoxic paraprotein: successful resolution by exchange transfusion.

Acute renal failure was diagnosed within 6 days of birth in a full-term neonate. The mother was known to have a monoclonal gammopathy, immunoglobulin G (IgG) lambda, discovered a year before pregnancy on being investigated for hematuria and proteinuria. Her renal function was intact. Maternal renal biopsy performed at the time showed a focal proliferative glomerulonephritis with nonfibrillary homogeneous mesangial and intramembranous electron-dense deposits. Immunoperoxidase staining was positive for IgG and lambda and kappa light chains along the glomerular and tubular basement membranes. Pregnancy was uneventful. Protein electrophoresis and immunofixation of the infant girl's serum and urine samples showed the presence of a paraprotein electrophoretically identical to that found in the mother. Exchange transfusion resulted in a rapid improvement of renal function in parallel to the disappearance of the monoclonal component.