C4B deficiency associated with membranoproliferative glomerulonephritis.

A 10-year-old girl was noted to have microscopic hematuria and proteinuria in 1986. As her urinary abnormalities were persistent, she underwent a renal biopsy on 4 occasions until 2003. Although the appearances of the renal biopsies were strongly suspicious of systemic lupus erythematosus, she never exhibited specific autoantibodies or distinctive symptoms. She received corticosteroid therapy and the urinary findings responded. The 4th component of complement remained low during the period of the observation. Both genotyping and allotyping analysis revealed complete C4B deficiency. Some case reports have mentioned renal disease associated with C4B deficiency and we consider the nephropathy in this case to be related to the C4B deficiency.