C3 nephritic factor can be associated with membranous glomerulonephritis

Background C3 nephritic factor (C3NeF) has been described in association with membranoproliferative glomerulonephritis and is involved in 80 % of cases of dense deposit disease. C3NeF is an immunoglobulin G (IgG) autoantibody which binds to the complement component 3 (C3) convertase C3bBb, thereby inhibiting its decay and leading to massive C3 cleavage. Commonly associated with C3NeF are low C3 levels, decreased total haemolytic complement (CH50) and normal C4 levels. C3NeF patients often present with proteinuria, haematuria and high blood pressure. Evolution to end-stage renal disease is common. Treatment consists of steroids and/or immunosuppressants, with variable efficiency. Renal transplantation is marked by histological recurrence, leading to higher rates of allograft loss. Cases We report C3NeF in association with membranous glomerulonephritis type 3–4 in two unrelated children. We also demonstrate that, under adequate immunosuppressive therapy, proteinuria is significantly lowered, blood pressure is kept within normal range and long-term renal function remains normal. Conclusions C3NeF can be associated with membranous glomerulonephritis in children. Clinical presentation is mild, and mid-term outcome is favourable under adequate therapy. However, complement anomalies persist for several years.