[1] Yokohama City Univ, Med Ctr, Dept Pediat, Yokohama, Kanagawa, Japan
[2] Toho Univ, Fac Med, Dept Pediat Nephrol, Ota Ku, 6-11-1 Omori Nishi, Tokyo 1438541, Japan
[3] Tokyo Metropolitan Childrens Med Ctr, Dept Nephrol, Tokyo, Japan
[4] Shiga Univ Med Sci, Dept Pediat, Otsu, Shiga, Japan
[5] Hlth & Welf Ctr, Kawasaki Saiwai Ward Off, Community Hlth Welf Div, Yokohama, Kanagawa, Japan
[6] Tokyo Metropolitan Childrens Med Ctr, Dept Clin Res, Tokyo, Japan
[7] Natl Ctr Child Hlth & Dev, Dept Nephrol & Rheumatol, Tokyo, Japan
[8] Teikyo Univ, Teikyo Acad Res Ctr, Tokyo 173, Japan