[1] Nara Med Univ, Dept Pediat, Kashihara, Nara, Japan
[2] Chugai Pharmaceut Co Ltd, Tokyo, Japan
[3] Natl Ctr Child Hlth & Dev, Div Hematol, Tokyo, Japan
[4] Ogikubo Hosp, Dept Blood Coagulat, Tokyo, Japan
[5] St Marianna Univ, Dept Pediat, Sch Med, Kawasaki, Kanagawa, Japan