Decreasing hypocomplementemia and membranoproliferative glomerulonephritis in Japan.

The number of patients with membranoproliferative glomerulonephritis(MPGN) diagnosed in our institution and the incidence of hypocomplementemia as determined by school urinary screening programs in Japan were investigated retrospectively. Fifty-seven children were diagnosed as having MPGN between 1974 and 1997. Of these, 13 patients were diagnosed during period 1 (1974-1979) and 25 during period 2 (1980-1985). A decreasing trend was observed during periods 3 (1986-1991) (12 patients) and 4 (1992-1997) (7 patients) compared with period 2 (P<0.05 and P<0.01, respectively). A significant difference was also noted when MPGN was compared between periods 1 and 2 (1974-1985) and periods 3 and 4 (1986-1997) (P<0.01). Serum C3 was measured in 1,282 school children with abnormal urinary findings between 1980 and 1997. Thirty children had hypocomplementemia. The incidence of hypocomplementemia was significantly lower in period 3 (1986-1991) (9 children) and period 4 (1992-1997) (2 children) compared with period 2 (1980-1985) (19 children) (P<0.05 and P<0.01, respectively). New cases of MPGN in our institution and the incidence of hypocomplementemia as determined by school urinary screening programs are decreasing in Japan. The reason for this trend is unknown.