[1] Great Ormond St Hosp Sick Children, Dept Bone Marrow Transplantat, London WC1N 3JH, England
[2] Great Ormond St Hosp Sick Children, Dept Haematol, London WC1N 3JH, England
[3] Cent Middlesex Hosp, Dept Haematol, London NW10 7NS, England
[4] Imperial Coll Fac Med, Dept Haematol, London, England